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View Full Version : Origin of COE as compatibility measure in studio glass


Lani McGregor
03-28-2005, 01:50 PM
Henry (you up yet?),

Dan tells me that you guys never talked about COE in the '60s in Madison.

He also sez that he thinks Harvey was (maybe) the first to import the German color bars, but he also never remembers hearing about COE in relation to those.

Where did this COE thing first come into studio glass? Specifically as it relates to compatibility? Any recollection?

-Lani

Henry Halem
03-28-2005, 04:52 PM
Harvey? not a chance. Dan should remember Barber was doing work with batch at Madison when we were there. Just got off the phone with Fritz and he believes it was probably Chihuly in about 67-68 that brought back color bars from Germany. Fritz knew about COE in 65 in Iowa and then when he got to Madison did work there with Barber on making glasses using The Schole's book Modern Glass Practice as the bible along with Weyl's book. Barber was the real whiz with the glass calculation though. He, Barber may have been doing glass calc. prior to 65 but we have no way of knowing as he's dropped off the face of the earth. Barber was doing his batching in 68 when I was there. So there really is no definitive answer to your question. A bottle of single malt might help me in doing more research though.

Lani McGregor
03-28-2005, 06:27 PM
Originally posted by Henry Halem
Harvey? not a chance. Dan should remember Barber was doing work with batch at Madison when we were there.
Yes, Dan still has those brain cells. And how could we forget Barber? He was production manager here for years. Bullseye’s own Raymond Babbitt.
Barber was the real whiz with the glass calculation though. He, Barber may have been doing glass calc. prior to 65 but we have no way of knowing as he's dropped off the face of the earth.
Now, now, be kind. Portland, Oregon (where Mr B still babbles) is not “off-the-face-of-the-earth.” I have it on good authority that it is three ‘burbs better than “Bum**** Nowhere”.
Barber was doing his batching in 68 when I was there. So there really is no definitive answer to your question. A bottle of single malt might help me in doing more research though.
Do you want that with a side of Jerk sauce or neat?

Seriously, there must be records – somewhere – as to when the color bars started being schlepped according to COE. Do you have any old product catalogues? Anyone else? Or are they all in Marvin’s attic?

Pete VanderLaan
03-28-2005, 10:18 PM
Robert Held made clear reference to C.O.E. in the '67 NCECA papers he did on phosphate opals. Dudley Gibberson was also referring to it in 67. I do think Fritz was Dudleys source and inspiration.. Paul Manners did his Custom Made to Fit article for Al Lewis's old magazine but it was always referred to as Linear expansion Co-efficient (L.E.C.) which is much more correct. It also appears in Morey and Scholes as Henry suggested. Dan was the first I recall making the suggestion that viscosity was explaining a lot about fit although Nick Labino was totally tuned into it from the getgo. I wish I still did single malts.

Dale did not bring kugler in until '73 actually and talked Benheim into handling it. Then Littleton got it and started selling it and Benheim returned it all in disgust. I first saw it when John Bingham was carrying it around in a mailing tube he brought from Orrefors. John had been a student at Goddard with Billy Happel and had spent a summer at Orrefors. That was in 1971, considerably earlier than Dale's effort to supply the RISD Students. If you'll remember RISD had that catalog with the melt samples and the barrels of SODA and LIME on the cover. That was '73.

No one actively talked about C.O.E. then. It was like this magic Isotoner stuff where "One size fits all"....except for the bright Reds and yellows, and all of those awful hotdog colors which fit nothing.

Henry Halem
03-28-2005, 10:54 PM
I have a vague recollection of Joel Myers having Kugler bars earlier than 73 but I couldn't swear to it. I'll try and contact him to find out. It would be intereresting to try and find out who did actually bring them in first.

Rick Sherbert
03-28-2005, 11:20 PM
I sat with Fritz and Kent Ipsen a few years back at VCU and got s-faced on some good whiskey and listened to them tell stories and wishing I had a tape recorder. The old timers aren't going to be around forever and it would be really nice to have a record (even anecdotal) of what happened in the early days, like when did Kugler arrive, who brought it in and who really did throw the trout into the Penland furnace....

Tom Littleton
03-29-2005, 12:15 AM
The story I always heard was that Kugler came to the US when David Hopper brought it back from Germany and got C & R Loo to import & sell it. The only thing I'm certain of is that HKL got into the business of importing and selling it as early as 81 and certainly was doing so in 83. I'd have to ask him if he brought any back for his own use before then. I think he was back and forth to Europe almost every year or so during the late 60s and 70s. He spent alot of time in Frauenau and it's not all that far from where Herr Kugler was.

I never heard of Benhein selling Kugler. They did sell Zimmerman and gave up after Olympic got some. However, at the time, one of the people at Benhiem also told me that they had serious safety concerns about the Zimmerman.

Durk Valkema
03-29-2005, 01:13 AM
Concerning Kugler colour bars I remember dragging loads over in January '68 when Sybren Valkema was the Visiting professor in Glass at Madison teaching "European techniques" and introducing tricks like uberfang and underfang with colour bars among other tricks.
Conpatibility with the e-glass was an issue, Harvey was melting a batch from Erwin in his own shop that worked better.

03-29-2005, 01:35 AM
This is like a trip down memory lane! I know we had our hands on some Kugler as early as '70 or '71. I don't know if we were getting it sent directly from Germany or from some other source. CRLoo was the earlist supplier that I can remember. I know there were times when we got a bulk order together with the University students and got straight from the factory. I think I still have a few chunks with those really old labels.
David Hopper was the first person I saw blow glass who knew what he was doing. We were just messing around until then.
I know Harvey had lots of Kugler around his shop and made pick up cups in '79. We certainly knew about fit and expansion before that and did lots of calculations to increase and decrease "LEC". Paul Manners paper was biblical material.

Henry Halem
03-29-2005, 08:02 AM
First of all it's Bendheim non Benheim. Kugler bars came here before Loo ever started importing. The only way you could get it was to order directly. You had to go to the Customs office and pick it up. If the person in customs didn't like you for some reason they made you pay 7% duty if you didn't look like a hippy you could just sign for it.
Durk, that batch that Erwin melted at Harvey's was a black and a white. Erwin made the most fantastic pieces of German expressionistic glass I ever saw. As I recall the glass was very and I mean very soft but for a reason, it all devitrified into a slimmy mass. David Hopper worked with Erwin in Germany and did make some fantastic work. I remember his white scultural pieces very much influenced by Erwin. In my estimation Erwin was a very important figure in the American glass studio movement and is not given enough credit. I will be in Penland this summer and if HKL is up to it I will go and pay him a visit and of course try and jog his memory of that time. Of course TL can do that now if cares to.

Lani McGregor
03-29-2005, 09:02 AM
What I’m still digging for - more even than the origin of Kugler importation - is where specifically in time COE/LEC came into the studio glass vocabulary as a term synonymous with compatibility.

Were the early Kugler bars referred to by a specific LEC? Were they marketed that way by C&R Loo et al?

When Hugh mentions knowing about fit and expansion, how was that measured? Theoretically, by calculation? Measured with a dilatometer? Or a number provided by a manufacturer? Were the early clear studio batches designed to fit Kugler? If so, how was that fit measured?

Was SPB the first commercially available batch in the US studio glass scene? What was it designed to fit? How was the "fit" measured?

In Europe what had Kugler been designed to fit?

To my knowledge, the American factories (Fenton etc) never used color bars, but melted their own color. How did/do they measure the fit/mismatch of their color?

Anyone know the date/issue of the Manners article in what Pete calls “Al Lewis’s old magazine” – was that “Studio”?

Incredible what that first cup of coffee will do to you.

Jon Myers
03-29-2005, 10:37 AM
I love this kind of thread.... I heard that Spruce was formulated to fit K61(white), is that true? As I'm reading this I'm thinking we're missing the boat by not having an organized oral history of the studio movement early days while we still can. Since we have the attention of a lot of smart folks here online we should put together a set interview questions and interviewees.
Some of the people who were instrumental were not book writers so their footprints will fade as the people who walked by, and directly behind them die off. One of the neat things about the internet is that there is a reader of this board within 100 miles of almost every major glass figure I can think of (which is not that many as I an new to this and don't know who did what 20 years ago hence the need for something like this(for me at least)) I would be willing to travel in the wintertime to work on something like this and I'd imagine that there are others who would like to get in on the fun....I'd love to have an excuse to talk to some of these folks....

Pete VanderLaan
03-29-2005, 11:10 AM
Scholes made the only presentation that the studio movement used. Books like Morey simply weren't being read. The early Kugler had NO references to expansion factors. It just magically fit. Expansion really entered the mainstream as something to measure after Paul's article. Again, Nick would always say he didn't know why high lead glasses had such tolerance, just that they did. Once Nick made the initial SP batch formula ( I believe SP92), expansion and compatibility became common in discussions in private shops, but not much in the schools that continued to say things like "It's OK to put the purple over the yellow but not the yellow over the Purple". In any of my time at Pilchuck- 77-78 it was never mentioned once. but the private shops that made their own color knew. I don't think at the time that private shops were much into casting and so the annealing- viscosity issues were not on the table. The Manners article really brought it upfront. These days if I talk about measuring viscosity, people's eyes glaze over.

Sorry about Bendheim. I really couldn't remember the spelling and tried it both ways. I do remember them having color rods way before Loo though. If it was Zimmermann, it's possible. At that time Zimmermann was flakey, cordy and sometimes stone ridden. We said it had character. I always liked their colors better than Klaus's.

I brought a load in once thru a friend stationed in Oberamagau and he was to ship us about 40 KG. His garage caught fire and the whole thing turned into one big block which he shipped us anyway. We would whack off chunks with a big chisel. I remember the airfreight and customs part too.

But Lani, why the interest outside of the fact that you guys have a proprietary interest and don't really think L.E.C. is all that critical compared to viscosity- which may be because you tend to work with big long flat sheets that can really drag themselves around a lot.

Henry Halem
03-29-2005, 01:52 PM
Originally posted by Jon Myers
I love this kind of thread.... I heard that Spruce was formulated to fit K61(white), is that true?
Not true!

Lani McGregor
03-29-2005, 02:00 PM
Originally posted by Pete VanderLaan
The early Kugler had NO references to expansion factors. It just magically fit.

Magic? During the time when Hopper visited the Eisch factory in 1969 (per David this AM) they were testing for compatibility two ways:

- the thread pull test (which, as we all know, measures the differences between glasses based on the combined factors of their viscosity and their expansion)

- a softening point test (which, not to insult anyone’s intelligence here, is also an indicator of viscosity).

I’d assume that Kugler - located so close to Eisch - if he was testing for compatibility at all, was using similar methods. But that’s an assumption. Maybe he was using magic. As you state, it appears that he was NOT using LEC.


Expansion really entered the mainstream as something to measure after Paul's article.

Again, I’d love to find this article. Got a date/issue number?



But Lani, why the interest outside of the fact that you guys have a proprietary interest and don't really think L.E.C. is all that critical compared to viscosity- which may be because you tend to work with big long flat sheets that can really drag themselves around a lot.

I’m not sure what you mean by “proprietary interest”. Can you explain?

And I’m also not real clear on what “big long flat sheets” have to do with it.

As to our not thinking LEC is critical, that’s NOT what Dan’s been saying. His sole argument is that it’s only half the story and has oddly become a standard with the inherent problems of all over-simplifications.

Why the interest?

A) material science/history curiosity

B) having to deal with the confusion/suspicion that continually results (what you call “eyes glazing over”) in trying to insert viscosity into the compatibility discussion.

C) marital discord: the other day as Dan was banging his head yet again against the kitchen wall trying to clarify LEC/viscosity relationships to my dull (and hugely unscientific) brain, I shrieked back at him in my best Fishwife voice “Aren’t you going to feel like an asshole if it turns out that this problem of equating the COE with compatibility really got going when you and that lame-ass ex-partner of yours wrote that stupid book in ’83 and suddenly [at least in our corner of the market] it was all “COE 90 glass and COE 86 glass” blah blah blah. Now that I’m hearing it’s all Paul Manners’ fault, I just need to find Mrs Manners and see whether LEC screwed up her marriage too.

So, where’s this article?

Steven O'Day
03-29-2005, 02:00 PM
Bendheim carried Kügler before Loo, but had a falling out about business practices. They picked up Zimmerman somewhat later, but Zimmerman went through a period of really awful quality control which was straightened out. They were also carrying Wiesenthalhütte which I believe at that time was made primarily for pressing jewels and other things and was not really made to be compatible. Eventually Bendheim was just not too interested in hassling with color anymore and gave it up.

I think the Swedish factories use the bars, but I don't know if this is a recent thing or not.

Durk Valkema
03-29-2005, 03:20 PM
Harvey and Erwin played around with the black and white while Erwin was there autumn '67. I distinctly remember clear glass in Harvey's shop spring '68, I will check.
Most factories' in Europe melted there own colours and made bars on the side for own use (at Orrefors Sven Palquist 'Colora" series in fuga technique 1953, and Gunnar Cyrén "Pop" goblets from 1966) but used Kugler, Zimmerman and others as well and simply adjusted the clear base to fit. Leerdam used to make bars for there own use. Donated the remaining 3-ton of it to the school later on.
I will check my father's notes to find out more and talk with the Leerdam chemist. The big change in Leerdam came after the war when the tableware production was automated and crystal production reduced. They did have a small test/colour furnace in the back of the crystal furnace though. This is where my father experimented with his students of the glass school (1943-52) and where he learned glass blowing himself.
As to compatibility, the early morning test was the thread pull, followed by the cylinder cut and tested after it annealed on the belt for 3 hours. For precise dating I will have to do some research.

Lani McGregor
03-29-2005, 03:37 PM
So - Hi, Durk! - was a connection between LEC and compatibility of glasses part of the discussion in European glass factories (then or now?) to your knowledge?

Pete VanderLaan
03-29-2005, 06:53 PM
well, I still have the article and I will copy it for you. I will have to find it however but I know which room it is in. It does make a gross error in that Paul used the English and Turner numbers which have really done a very good job of standing the test of time BUT he then included the Winkelmann and Schott numbers for colorants as well. Those numbers were created for the enamelling industry and utilized an entirely different range in which to measure the expansions. They comedy of errors was compounded by Glassnotes using those numbers as well and they don't have anything to do with the real world. Simply put, there are no values for metallic oxides that are used as colorants. Industry never cared since they never planned to case colors with clear as a production item.

I really think that L.E.C. works so well for glass blowers that the viscosity issues have just about never concerned them. Not many people make the connection between viscosity and annealing ranges in thinner ware. In casting, you guys have to anneal forever , only to open the kiln and find the piece cracked which tends to make one ponder the issues at hand a good deal more. There is a lot going on. Glassblowers really get instant gratification and when things don't fit, usually you know pretty quickly. In that capacity, I don't think that Dan's observations about viscosity being the flip side of the coin will ever gain much traction. That is not the same as saying that the observations aren't correct, I think they are.

Where I think the problem lies, is in the gross generalization that such things as "96" guarantee you a clear blue sky and great sailing. I was just talking to Henry about a zinc sulphide cad sel red that is in the last edition of GlassNotes. It is a very nice red, but the L.E.C. is about 114. Cad sels really have to have at least three percent zinc in them to work well, or at least I've never seen one work with less zinc than that. That in itself is OK but if you want to make that glass color into a 96 as well, it's going to be kind of stiff to work while the clear is fairly runny. That tells me something about the likelyhood of mixing those glasses in really thick pieces as being problematic. Theyu do however work well in blown ware.

As to Mrs Manners, She and Paul long ago divorced and the last time I had heard a thing from Paul, he had quit glass and was teaching kindergarden and playing beach volleyball.. Then he vanished entirely. Anyone knowing his whereabouts, please tell me. I haven't heard a word since 1986.

Pete VanderLaan
03-29-2005, 07:19 PM
Glass Art Magazine August 1973. Great issue. the article talks about matching "Drykiln Crystal A" cullet. Also a very nice picture of Kathie Bunnell and an ad for bullseye glass selling opal colors and clear colors for 1.85 sq ft. Also Bob Biniarz teaching a summer class at the Archie Bray Foundation.

Lani McGregor
03-29-2005, 07:43 PM
Originally posted by Pete VanderLaan
Glass Art Magazine August 1973. ...an ad for bullseye glass selling opal colors and clear colors for 1.85 sq ft...

OK, Pete, now we are into magic: Bullseye wasn't founded until 1974.

Tom Littleton
03-29-2005, 11:44 PM
Henry,
HKL won't get back from Florida for at least a couple more days. He's had a fun winter trying to rebuild his apt and gallery that the hurricanes blew away but now my mom wants to get back to NC. Soo.. It'll be a little while fore I can ask him anything.

As for the original formulations of the labino formula othewise known as sp batch, and again this is as I remember, Nick gave us the original formula as a "chemical" formula and not a list of materials. We had to convert it to a list of materials and we had our first test melt run at Penland. Bill Worchester was there at the time and It did not melt well. We got a different mesh silica and added the Lithium at Labino's suggestion. With those changes, we ended up with the formula now known as the 92. The 92 turned out to be less than Ideal. Sooo.. The expansion was lowered and I always thought we had tried to match the Kugler 61 as it was the most popular color. However, I was not the one that was actually doing the work. This new batch formula had a theoretical expansion of 87 so that is what we called it.

Henry Halem
03-30-2005, 08:03 AM
The original SP had very high Lithia as you say suggested by Nick but because the viscosity was so low it ate everyones tanks and pots like pak man. You reduced the lithia and voila SP87.

Robert Mickelsen
03-30-2005, 09:02 AM
Glassblowers really get instant gratification and when things don't fit, usually you know pretty quickly. In that capacity, I don't think that Dan's observations about viscosity being the flip side of the coin will ever gain much traction.

Pete, as a flameworker who is accustomed to much more instant gratification than even glassblowers get I want to respectfully disagree here. I am *very* interested in this thread and am following it closely. There have been issues with borosilicate glass fits that justify the validity of viscosity as a factor in fit, even in low-expansion borosilicate glass. For instance, there is an opal green that is notorious for crackling when incased. But the measured LEC is dead-on that of clear boro glass. Why doesn't it fit? The only answer, and what I have been telling students for years myself, has to be variations in the viscosity curve of each glass.

Fascinating discussion folks. Please continue...

Bruce Troeh
03-30-2005, 09:08 AM
While Iowa State still has the glass facility it no longer offers glassblowing except through the Glasblowers Guild. I started in 1977 learnign (sp) about formulating batch and calculating COE with Dr. David Martin. At the time I remember one of the grad students had purchased a box of kugler color I dearly wanted to use. Our batch was 111 - 113 COE. I do remeber a few broken pieces.
I've got a box of kugler to play with now but I'm using 104 so it still sits. BTW. Bruce

Tom Littleton
03-30-2005, 09:16 AM
Henry,
That is not correct. Where did you get your info?

I have to say we got lucky with a short learning curve but we did have Nick's help. The first stuff that got melted at Penland was made to the orginal formula and which had no lithium. As I remember, the stuff was so hard to melt it got cooked at high temp for 24-36 hours perhaps the source of you stories. We were trying a relatively large grain local sand. We tried screening that sand to get a smaller grain but that didn't work. I remember only two people got some of those first runs. We tried changing the source of the sand and added the lithium at the same time and by the way it was the maximum amount suggested. We should have tried changing one thing at a time and used less lithium and then increasing it in a series of tests but that was not done. The result was the 92. We only took out a little soda to make the 87.

Pete VanderLaan
03-30-2005, 09:43 AM
Originally posted by Lani McGregor
OK, Pete, now we are into magic: Bullseye wasn't founded until 1974.

well, you are right. I actually included the items from a few other issues that popped up just for effect. The price on the glass was right though. I do have the ad announcing the grand opening of bullseye.
40th anniversary indeed!

Dave Bross
03-30-2005, 09:54 AM
Wow! spectacular thread! Do continue!

If anyone has that book that HKL did in the late sixties there is a lot of discussion of what went on with Erwin at the factory as regards melts. I read the book a few years back in the Seattle library so I don't have a copy to reference now.

Tom,

Are there any other reasons besides expense of material that you wished you had used less lithium?

Durk Valkema
03-30-2005, 09:54 AM
Just spoke with my friend the chemist at the Leerdam plant.
In his memory Kugler colours where used in the Crystal production all the time. Kugler was asked to make a melt to fit but if it did not the clear was adjusted.

It was tested by production doing the ring test.
The lab used the "method Dr. Patmos". Dr. Patmos worked for Philips and developed a test where a standard clear was welded to the glass to test. After annealing the weld was cut and polished and viewed through a micro polariscope to measure the tension.
Necessary for the developments of all the different light systems Philips developed.
This is all pre 1950.
His remark on the COE, LEC and viscosity was very practical, to my friend its all very theoretical if you know the LEC you know the COE and for him viscosity has to do with machine speed. Than again he is all about container glass. Density of 2.5 at room temperature but only 2.25 at 1400 C (2552F)
Batch calculations with expansion is only practical empirical info, measure and you will know.

Pete VanderLaan
03-30-2005, 09:55 AM
Originally posted by Robert Mickelsen
glass. For instance, there is an opal green that is notorious for crackling when incased. But the measured LEC is dead-on that of clear boro glass. Why doesn't it fit?
Fascinating discussion folks. Please continue...

When you say it is dead on, who measured it and how. Is it a pull test? I simply do not trust pull tests in opal/clear matches as even remotely reliable. They only work in formulas of similar composition. It would require dilatometry or a ring or trident seal test to get accuracy here. Chrome glasses are refractory in nature and the problem is compounded by opacity. If it is a boro supplier, I have so far not been overwhelmed by the current group of suppliers being terribly thorough. It's a comparatively young industry when it comes to color and actual batching of colors.

Lani McGregor
03-30-2005, 10:45 AM
Originally posted by Pete VanderLaan
I really think that L.E.C. works so well for glass blowers that the viscosity issues have just about never concerned them.

Pete, IMO what works well for glass blowers is glass blowing. Not LEC. I happen to know three glassblowers who started a glass factory and found out – while trying to fit different colored glasses together in streaky sheets – that after sending in numerous tests to laboratories (late ‘70s) they could only make the glasses match by INCREASING the difference in their COEs (0-300C). Everything they thought they knew about expansion and fitting colored glass had only taken them in the wrong direction.

Where I think the problem lies, is in the gross generalization that such things as "96" guarantee you a clear blue sky and great sailing.

Exactly. COE is half of it. Viscosity is the other half. One without the other is certainly a place to start, but is misleading. Matching COEs only works if the base compositions are the same or very similar. Who can make a broad color palette with only one base composition? Bullseye has at least five different base compositions for its line of colored glass. If we made the expansions the same on each of these they’d be grossly incompatible.

At the time BE developed its Tested Compatible line Boyce (ever the salesman) liked to call it “90 COE” and, IMO, intended to take over the kiln world at that “expansion”. Dan was never completely comfortable with the corruption of glass science entailed in that kind of marketing. Of course they could have called the glass “990 AP” instead of “90 COE” and been equally right – and equally wrong. For accuracy, it would have been more accurate to call it a 90/990 glass.

I’m just curious as to where the COE as a synonym for compatibility first entered the marketplace and hot shop. When did color bars or batch start to be listed/distributed in those terms?

And I’m talking measured (i.e. at 0-300C) not theoretical or calculated COE. Lots of people were doing calculations. But to our knowledge the practical testing done in factories on a daily basis has always measured the “fit” between glasses, i.e, the combination of expansion and viscosity – NOT the COE.

When did SPB first list a measured COE? I’m pretty sure that what Tom and Henry are talking about in terms of Labino’s formula is calculation.

Robert Mickelsen
03-30-2005, 11:24 AM
Originally posted by Pete VanderLaan
When you say it is dead on, who measured it and how. Is it a pull test? I simply do not trust pull tests in opal/clear matches as even remotely reliable. They only work in formulas of similar composition. It would require dilatometry or a ring or trident seal test to get accuracy here. Chrome glasses are refractory in nature and the problem is compounded by opacity. If it is a boro supplier, I have so far not been overwhelmed by the current group of suppliers being terribly thorough. It's a comparatively young industry when it comes to color and actual batching of colors.

I know the green was tested on a dilatometer and was on the money. The color manufacturers have tried for years to solve the problem to no avail. You are absolutely correct in what you say about the present group of suppliers.

Lani McGregor
03-30-2005, 12:18 PM
Originally posted by Pete VanderLaan
When you say it is dead on, who measured it and how. Is it a pull test? I simply do not trust pull tests in opal/clear matches as even remotely reliable. They only work in formulas of similar composition. It would require dilatometry or a ring or trident seal test to get accuracy here.

Just so we're all straight on what's being measured:

a DILATOMETER is used to measure the expansion, e.g. COE(0-300C) or “LEC”. This is the measurement of an isolated glass.

The following three tests measure the combined effect of expansion AND viscosity on two different glasses:

RING TEST

TRIDENT SEAL TEST

BULLSEYE’S CHIP/BAR TEST

The PULL TEST is also a rough measure of the combined effect of expansion and viscosity on two different glasses, BUT in our factory experience it is very frequently unreliable due to on the skill level (or lack thereof) of the person performing the test.

Pete VanderLaan
03-30-2005, 12:21 PM
Originally posted by Lani McGregor
terms?

And I’m talking measured (i.e. at 0-300C) not theoretical or calculated COE. Lots of people were doing calculations. But to our knowledge the practical testing done in factories on a daily basis has always measured the “fit” between glasses, i.e, the combination of expansion and viscosity – NOT the COE.
*************************************
When did SPB first list a measured COE? I’m pretty sure that what Tom and Henry are talking about in terms of Labino’s formula is calculation.


Actually you have hit on the first point of confusion. How about 17C-300C instead. When I did the work at Los Alamos labs with this, we started at 0C just like the ASTM standard would have suggested. Nothing made real world sense. Once I shifted to 17C as a start point, things looked right. 17C is of course the temperature at which lab workers are comfortable while wearing white coats. I have to be very careful when I'm measuring four inch rods for expansion that the start temperature is consistent. In summer, it easily goes up to 23C so I need a cooling bath for the canes and dilatometer.

The labino stuff is calculation and it is consistent with the E&T numbers if run up to 250C ( I think). E&T did not originally go to 300C and that's why those numbers have never made real world sense. It seems to me it was either 250C or 225C. I cannot recall right now and I don't want to look it up.

When Croucher and I sat down about eight years back to talk about expansion we both felt that a 93-93.5 would have been a better standard but SP87( which is really a 96) was the elephant in the room. If we wanted to sell color that was not 45 percent lead we were going to target SP87. While Kugler just got around the fit issue by dumping lead into the glasses, we really wanted lower lead contents wherever possible and no lead if it was not critical to the glass. Kugler and company all use GLASMA 70 or 71, I forget which but it is their proprietary batch. It has a predetermined L.E.C which they add colorants to. It explains why Kugler is all over the map. John and I both made the color first, and then adjusted the glass to a 96.

I agree about the multiple formulas. I have six base glasses. I think John had seven the last time we talked. The trouble with the viscosity issue is that I can't explain it. Nick couldn't explain it. Why did lead seemingly defeat the compatibility problem up until you pierced the surface tension of the piece with a saw or a grinder? Would a high Bismuth glass do the same thing ( moot since bismuth is too expensive).

I don't think anyone listed an L.E.C. on their stick until Croucher. I never did. I advertised its expansion but never put it on the rod. I liked the parrots too much.

Maybe glassblowers are more like the tarot card of the fool. Walking towards the cliff and always the presumption that they will turn at the last minute without ever knowing the cliff was there.

Pete VanderLaan
03-30-2005, 12:26 PM
Originally posted by Robert Mickelsen
I know the green was tested on a dilatometer and was on the money. The color manufacturers have tried for years to solve the problem to no avail. You are absolutely correct in what you say about the present group of suppliers.
***************************
Is this that green that was a square stick and came from the phillips plant in NY along with the opaque white stick about three years back? Secondly , who did the dilatometry tests? Do you really know firsthand that it was tested? That's what I mean about the suppliers.

Lani McGregor
03-30-2005, 12:51 PM
Originally posted by Pete VanderLaan
John and I both made the color first, and then adjusted the glass to a 96.


Pete, I’d still argue that you weren’t adjusting to a 96 COE, you were adjusting to fit SP87.

Do all glasses with a 96 COE fit SP87?

And you think viscosity is confusing?

BTW what’s the AP of SP87?

Originally posted by Pete VanderLaan
Why did lead seemingly defeat the compatibility problem up until you pierced the surface tension of the piece with a saw or a grinder?


I don’t understand how the compatibility problem is even “seemingly” defeated if it’s only compatible until you cut into it.

Steven O'Day
03-30-2005, 12:55 PM
In the mid 80's Therese LaHai was at CR Loo and wanted to try and figure out the in-compatability problem. She had the base glasses and colors tested and published the COE numbers in the catalog as a rough guide. I don't remember any talk of viscosity. I think at the supplier level before this it was caveat emptor, the numbers used were the ones from the manufacturers or the E & T theoretical.

Pete VanderLaan
03-30-2005, 01:06 PM
Originally posted by Lani McGregor
Pete, I’d still argue that you weren’t adjusting to a 96 COE, you were adjusting to fit SP87.

Do all glasses with a 96 COE fit SP87?

And you think viscosity is confusing?

BTW what’s the AP of SP87?



I don’t understand how the compatibility problem is even “seemingly” defeated if it’s only compatible until you cut into it.
*********************
That's why I said that the viscosity issue has never gained any traction. Glassblowers seem to be content with the notion that they can't cut and grind their work made with a lot of german color rods. It's bizarre but people seem very accepting of it. I don't disagree with you. It would seem as long as it doesn't actually explode, it's OK. How many people have you seen who still try to use bright canary yellow opal from Kugler. It doesn't fit anything on the planet. It still sells and if you don't grind it, it holds together for some time if you use cullets that are nearer to a 90.

I have been a vocal minority for a loooong time that the glass made in the 70's and 80's well may be the cullet of this century in due time. It's like pushing back the tide. I am simply stating the way I perceive things to be.

As to all glasses that have 96 C.O.E. fitting Sp87, no I don't think that but I think it based on the thickness of the two glasses that are present. I make opals at 96 that saw and grind with SP87 just fine if they are under one inch thick. Go over that and they don't fit. Why? my hunch is annealing range, not point.

You live in a casting world where thickness is a day to day issue. Things crack. They don't crack in blownware and the schools have absolutely no technical interest in this crap at all anymore. They have all adopted Dale's out of sight out of mind approach to broken glass.

As to the argument about what we were aiming at, I measure my glasses as a 96 on a dilatometer. I do that because I can usually measure SP87 as a 96 or very close. I make the number my target these days. I don't actually have any SP87 in the building right now and haven't for about a year. If SP varies, and it does occasionally, I simply can't try to follow the day to day vaguries of the soap opera. I need to be within 1.5 ten thousandths., that's all.

The annealing RANGE of SP87 is about 890 to 945 depending on thickness and how fast you want to anneal it. I put away large grinding blanks that are thick at 995 for about an hour before dropping to 940. If I don't, I have really cracking issues on grinding them or I have to anneal them at 940 for way to long a time.

When Croucher and I made our presentations at Corning back in 2001, Frank Wooley, senior melt engineer at Corning was there and got into the Q &A very actively. I made the assertion that a substantial number of "Checks" in pieces were really being mistaken for incompatibility when they were actually annealing problems. Frank became very animated in agreement. We talked about it for some time.

Tom Littleton
03-30-2005, 01:39 PM
Dave,
Expense is the biggest reason for not wanting to use a relatively large proportion of lithium but it also has a bad rep as a very aggrssive flux. My feeling is though (without actual data to back me up) that by the time you replace the fluxing action of the lithium with something else whatever you come up with will be just as corrosive.

Lani,
I can't remember when I started putting a measured COE in the sales material. I think fairly recently and likely when everyone else started talking about COEs and stuff and started to look at the 87 as a standard. No more than 8-10 years at the most but I'd have to check and I didn't always keep good records of when I made changes. It seems like it became more of an issue when the Dichroics came out and people wanted to use them in their furnace worked glass and the 90 standard stuff would not work with the SP 87. And likely after Pete learned how to build and operate a a dilatometer.

Lani McGregor
03-30-2005, 02:04 PM
Originally posted by Tom Littleton

Lani,
I can't remember when I started putting a measured COE in the sales material. I think fairly recently and likely when everyone else started talking about COEs and stuff and started to look at the 87 as a standard. No more than 8-10 years at the most but I'd have to check and I didn't always keep good records of when I made changes. It seems like it became more of an issue when the Dichroics came out and people wanted to use them in their furnace worked glass and the 90 standard stuff would not work with the SP 87. And likely after Pete learned how to build and operate a a dilatometer.

Tom, thanks. This is the input I was looking for. COE as a measure of compatibility seems to have showed up in the vocabulary of studio glass very recently (certainly quite a while after BE published Glass Fusing Book One in 1983 and our side of the market – i.e. kilnworkers - grabbed the “shorthand” tag of “90 fits 90” with all its half-accuracies and commercial agenda).

I'm not saying that the batch or color manufacturers are wrong to provide COE info, just that users think this equates to compatibility when any colored glass maker knows it doesn't.

Tom, do you provide an Annealing Point for SP 87? (Not the annealing range – the AP as determined by the ASTM test)? A softening point?

Durk Valkema
03-30-2005, 04:00 PM
"Kugler and company all use GLASMA 70 or 71, I forget which but it is their proprietary batch. It has a predetermined L.E.C, which they add colorants to. It explains why Kugler is all over the map. John and I both made the colour first, and then adjusted the glass to a 96."
That's Bullshit
Excuse me but Kugler was there decades before Glasma ever was thought of. Kugler started to line up with Glasma just to provide a base glass that would hopefully fit there range of colour glass to all of those studio melters, if people where able to melt it in the first place.
The basics of "Kugler crystal" mixed by Glasma has absolutely nothing to do with the different base glass that Kugler Colour or rather frau Fridrich develops her colour ranges around, other than the two fit most of the time hopefully.

Justin Watermann
03-30-2005, 04:01 PM
I just wanted to say I've spent the past hour and a half of my work day reading this, its more fascinating that the history channel and the military channel put together (and if you know my love of weaponry and old stuff that says alot). So thanks guys, and yes I'd be interested in researching or helping to organize info if anyone wants to try and put together some kind of documentry archive of it all.

Justin

Robert Mickelsen
03-30-2005, 05:45 PM
Originally posted by Pete VanderLaan
***************************
Is this that green that was a square stick and came from the phillips plant in NY along with the opaque white stick about three years back? Secondly , who did the dilatometry tests? Do you really know firsthand that it was tested? That's what I mean about the suppliers.

No, it is an opal green (NS jade) manufactured by Northstar. Paul Trautman did the dilitometer tests in an attempt to discover the reason for the cracking problem. I believe he did them and related the true results to me because there was no reason for him not to. I might be suspicious if I were not such a close friend of his. He divulged the results to me while were discussing what the problem could be if not the LEC. That is when we first discussed the possibility of viscosity curves... which is why bells went off when Lani mentioned it.

I might be wrong... the jade problem may be entirely different from what is being discussed here... but I am still reading this thread egerly every day (instead of working like I should be) anyway.

Dave Bross
03-30-2005, 05:56 PM
Thanks Tom.

I'll bet your assumption about whatever flux you use being equally corrosive is probably true. I suspect the amount of alumina in the glass is important here too.

One other thing Pete has (repeatedly) had to remind me about is that our old friend viscosity is THE major player in how fast the glass will eat the pot.

So there's one thing "for sure" about viscosity.

Lani,

While we're in history channel mode, who solved your expansion/viscosity fit issues in the early days and how?

Pete VanderLaan
03-30-2005, 06:09 PM
Frank Wooley had said to me that no chemical was particularly more corrosive in a glass than any other but it was the viscosity of the glass at a fixed temperature that determined how quickly a pot was attacked. In that capacity I think you could assume that Lithium is a very powerful flux for lowering viscosity. A little goes a long way.
As to the GLASMA issues, what Durk says goes contrary to what I have been told over the years. I was told that GLASMA became involved when German environmental law blocked the mixing of the base formulas in Germany. At that time the mix moved to GLASMA and much was standardized. If this were not the case, then it would be inexplicable to me that the company would make so damn many different expansion coefficients. It is not hard to standardize them if one can simply adjust the formula but if it's premixed then you have problems. When Klaus sold the company, my impression was the sale of a formula box and little else. The product suffered quality issues for years and produced a sufficient amount of defective product to cause US suppliers to stop dealing with them. As far as I could see at the time under Frau Fredrich, there was an apparant lack of control over process. They have gone on to build a large factory and try a variety of processes such as cast rod which have had genuine problems.

Pete VanderLaan
03-30-2005, 06:12 PM
Originally posted by Robert Mickelsen
No, it is an opal green (NS jade) manufactured by Northstar. Paul Trautman did the dilitometer tests in an attempt to discover the reason for the cracking problem. I believe he did them and related the true results to me because there was no reason for him not to. I might be suspicious if I were not such a close friend of his. He divulged the results to me while were discussing what the problem could be if not the LEC. That is when we first discussed the possibility of viscosity curves... which is why bells went off when Lani mentioned it.

I might be wrong... the jade problem may be entirely different from what is being discussed here... but I am still reading this thread egerly every day (instead of working like I should be) anyway.

*************************
Draw me several feet of cane of it, about 4mm in diameter which is around the thickness of a lead in a pencil. Vary it up and down a bit in thickness to be sure, I will test it.

Steve Stadelman
03-30-2005, 06:19 PM
Paul has not had Northstar for a while now. Is it an old batch?

Rollin Karg
03-30-2005, 06:43 PM
Originally posted by Robert Mickelsen
For instance, there is an opal green that is notorious for crackling when incased.
Robert, if that green is a fluorine opal this may help.
Years ago when we first started making colors a guy told me that the fluorine opals are made of billions of little fluorine inclusions.When you reheat you start to lose these little inclusions to the atmosphere and the more you heat the more you lose. Also the hotter the flame the more inclusions you lose and when you lose these little guys you change the LEC. The same thing happens in the pot when we make them. The longer they stay in the pot the more the LEC changes and most likely the viscosity changes too.
I remember how we were struggling to make the colors work at the time and that bit of news was just one more thing to torture us.
Rollin

Henry Grimmett
03-30-2005, 07:11 PM
Robert,

The jade green was never tested for COE by Paul. It was tested by 2 other people who wanted to know about the glass. Both found the glass to be in the 35 range.

The glass does not contain fluorine and the cracking in the early days (prior to mid 98) was poor formulation. After that date the cracking was closely related to reduction during working or phase seperation issues during extended "garaging" at high temperatures.

And yes, the viscoity curve and rate of heat loss during cooling of the borosilicate glass is very important to fit, maybe more so since the metal oxides tend to much denser in the boro glasses than in the soda-lime.

03-31-2005, 12:51 AM
I was told, by whom I have no idea, that the fluxing power of the alkalis has to do with ion diameter and the ability of the ions to enter and spread the tetrahedral bonds of silica. My copy of Handbook of Chemistry and Physics doesn't have data on ion sizes, but it is almost as old as I am. Do recent editions have such info? Which is larger among sodium, potassium and lithium? Does it make sense with expansion and what we know about fluxing power?

Durk Valkema
03-31-2005, 12:58 AM
Pete,
You get two stories mixed up here.
GLASMA was set up towards the end of the 70th to solve the environmental problems around the batch rooms of the Swedish manual glass industry.
Klaus had to close down his colour factory in Germany because the small industrial area got enclosed by housing estates and he had no space to expand into filters et all.
He sold the business to Fridrich & Schebler since they had a factory producing colour bars and rods for buttons and lampworking. The technology there was very primitive compared to the high tech set up Klaus had been running.
More than 10 years ago they invested millions in a new production facility complete with the latest in environmental technology.
They mix and melt there range of glasses there on the premises.
Just as a service to primarily the studio's they have GLASMA produce a pelletised batch that should fit most of their colours most of the times.

Klaus never indicated numbers for compatibility just an indication "Harte W" which you could read as an indication for viscosity because it indicates if it's a hard or soft glass. To bad Klaus passed away last year, but I will try to find out more about the origins.

Richard Huntrods
03-31-2005, 01:31 AM
I don't know about fluxing power, but if it's ion size you're after, that's a simple function of the number of protons & neutrons in the nucleus, as well as the number of electrons in the various orbitals.

A periodic table of elements is all that's necessary

http://www.webelements.com/

In essence, down is larger in any column, so it's Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs), Francium (Fr). Also, sideways is also larger for a given row. (i.e. Magnesium (Mg) is bigger than Sodium (Na).

Does this gibe with fluxing power (i.e. Sodium larger than lithium, etc)?

Cheers,

-R

03-31-2005, 03:23 AM
Ion diameter and molcular weight might not be related in the way you suggest. Since lithium is a light atom, it's internal forces are weak. I think it is the larger ion even though it is the lighter element. I would need to see some data though to be sure. Can anyone help here?

Lani McGregor
03-31-2005, 08:30 AM
Originally posted by Bruce Troeh
While Iowa State still has the glass facility it no longer offers glassblowing except through the Glasblowers Guild. I started in 1977 learnign (sp) about formulating batch and calculating COE with Dr. David Martin. At the time I remember one of the grad students had purchased a box of kugler color I dearly wanted to use. Our batch was 111 - 113 COE. I do remeber a few broken pieces.
I've got a box of kugler to play with now but I'm using 104 so it still sits. BTW. Bruce

But these were theoretical CALCULATIONS, yes? Did you ever MEASURE the COE back then? I.e., with a dilatometer?

This is definitely the basis of a lot of the confusion: the difference between calculated and measured COEs. The imagined compatibility between glasses of the same expansion in today's studio/marketplace is based on comparing MEASURED expansions.

And what I'm digging for is WHEN did the measured COE become the standard for compatibility in studio glass?

Lani McGregor
03-31-2005, 08:41 AM
Originally posted by Durk Valkema
Klaus never indicated numbers for compatibility just an indication "Harte W" which you could read as an indication for viscosity because it indicates if it's a hard or soft glass. To bad Klaus passed away last year, but I will try to find out more about the origins.

Wow, very interesting! Thanks, Durk!

I assume "W" = weich (soft)

So Klaus Kugler was comparing - or categorizing - his colored glasses based on the differences in their viscosities (hart/weich - hard/soft), NOT on their COEs.

Did that information travel with the bars? Does anyone who used Kugler in the '70s or '80s remember these ratings?

Tom Littleton
03-31-2005, 09:18 AM
Lani,
From Frank Woolley (data from a Melt at the Studio at Corning in 1997). Softening point 666 degrees centigrade(1231degrees F), Annealing point-492 degrees centigrade (918 degrees F), strain point-455 (851 degrees F), expansion (0-300 degrees) 94.9.

CAVEAT- None of these figures should be taken as gospel, a holy grail, something that everyone is going to get every time they melt. Variations in raw materials, frunaces, melting techniques and other factors will cause differences in the glass. Not to mention Frank told me that the dilatometer measurements were plus or minus one point in accuracy.

Have I put enough qualifiers in here yet?

Lani McGregor
03-31-2005, 09:28 AM
Originally posted by Pete VanderLaan
*********************
As to all glasses that have 96 C.O.E. fitting Sp87, no I don't think that but I think it based on the thickness of the two glasses that are present. I make opals at 96 that saw and grind with SP87 just fine if they are under one inch thick. Go over that and they don't fit. Why? my hunch is annealing range, not point.

Pete, the Annealing Point of a glass is a very precisely defined indicator of the viscosity of a glass (and of course, it determines the RANGE). So we are agreeing: the compatibility problems you sometimes encounter when you match measured COEs relates to their VISCOSITY differences.

You can try to compensate for the incompatibility problems of COE-matched glasses by better annealing practice, but you’re still screwing with glasses that are basically badly matched because they haven’t taken viscosity into consideration at the start. And you can very likely get away with it in blowing (or torchwork), but it comes back to bite you in the butt when you get thicker or grind – which is what lots of people are doing currently. At the same time that they’re kidding themselves that their matching COEs guarantee they’re working with compatible glass.

The annealing RANGE of SP87 is about 890 to 945 depending on thickness

Pete, I’m asking for the Annealing POINT. It’s a laboratory measure of viscosity that we can use to compare the relative viscosities of different glasses. It’s not an “about” number and it’s not a range (although I’d guess there might be slight variation depending on the lab used for the measurement).

For Bullseye, for instance, the AP of our clear is 990F, our white opal is 937F, our lead-based gold-pink transparent is 927F. Because of these annealing point differences, we have to adjust the expansion (to 91, 88 and 85 respectively) in order for the glasses to fuse together without visible stress in the daily compatibility tests. If we adjusted all those glasses to the same COE (believe me we’ve done this), they’d break apart.

Lani McGregor
03-31-2005, 09:34 AM
Originally posted by Tom Littleton
Lani,
From Frank Woolley (data from a Melt at the Studio at Corning in 1997). Softening point 666 degrees centigrade(1231degrees F), Annealing point-492 degrees centigrade (918 degrees F), strain point-455 (851 degrees F), expansion (0-300 degrees) 94.9.

CAVEAT- None of these figures should be taken as gospel, a holy grail, something that everyone is going to get every time they melt. Variations in raw materials, frunaces, melting techniques and other factors will cause differences in the glass. Not to mention Frank told me that the dilatometer measurements were plus or minus one point in accuracy.

Have I put enough qualifiers in here yet?

Perfect! Thanks heaps, Tom! So what you've got - IF all the qualifiers are taken into consideration - is a glass with a 94.9 COE and an AP of 918F.

I'd wager that any colored glasses that fit that base clear (i.e. show little stress in a ring, pull, Trident seal or BE chip/bar test) but have a much lower AP (such as a lead glass would) will NOT have a 94-95 COE. Their measured LEC (0-300C) will be lower.

Richard Huntrods
03-31-2005, 11:03 AM
Well, Tom - I'm a fan! I did the bending test when I first set up my annealer, and it resulted in me using my annealer at 915F. I give the glass a 1 hour soak and then ramp 100F/hr down to 50F. So far, so good as they say!

Gotta love that Spruce Pine!

-R

Originally posted by Tom Littleton
Lani,
From Frank Woolley (data from a Melt at the Studio at Corning in 1997). Softening point 666 degrees centigrade(1231degrees F), Annealing point-492 degrees centigrade (918 degrees F), strain point-455 (851 degrees F), expansion (0-300 degrees) 94.9.

CAVEAT- None of these figures should be taken as gospel, a holy grail, something that everyone is going to get every time they melt. Variations in raw materials, frunaces, melting techniques and other factors will cause differences in the glass. Not to mention Frank told me that the dilatometer measurements were plus or minus one point in accuracy.

Have I put enough qualifiers in here yet?

Dave Bross
03-31-2005, 11:38 AM
Random bits from the Lithium chapter in Volf's "Chemical Approach to Glasses':

"It's low ionization energy is indicative of the strongly ionic nature of it's bonds. Lithium differs from the other alkalai metals in the properties of it's compounds and it's behavior in glass.

In its behavior in glass,Li is more similar to Mg than to Na or K. Lithium and magnesium have similar effective radii,and are functionally substitutable, in particular in glasses with low dielectric losses, and both decrease the liquidus temperature of basic silicate glasses in the range between 2 and 4% of the oxide."

(My note here: lowering the liquidus temp. lowers the annealing point that Lani is talking about up above, and in what I've been melting, way less than 2-4% lithium will drop the anneal temp.)

"Li2O is the lightest oxide component of glasses, being twice as light as Na2O. Replacement of Li2O for Na2O or K2o, or assesment of the effect of Li2O on the physical properties of glasses, should therefore be considered on a molar basis only. The effect of Lithium in glasses is first of all given by its small effective radius, which is the smallest among the monavelent metals. "

" The small size of the lithium ion also facilitates diffusion into the glass by substitution for Na and K both below and above the transformation interval. The process results in a permanent compressive tension in the surface, which has become the basis of chemical strengthening of glass products."

( my note here: You have to wonder if this wasn't in Nick Labino's mind when he suggested the lithium to Tom and family for tuning up the final version of Spruce Pine. Nick knew that studio artists would be attempting to combine all sorts of odd glasses and may have figured some " permanent compressive tension in the surface" would be a very good thing.)

"As a result of a strong attraction to oxygen, lithium tends to contract the free spaces in the silicate network. This contraction, for example, leads to a greater effect of Li on the density of glass than would be expected theoretically.

Owing to its small ionic radius the field strength of Li is the greatest among the alkalai metals. Li is therefore strongly bound in the silicate network, as indicated by its improving effect on the chemical durability with respect to water and acids in both glass and enamels. The properties that increase with increasing bond strength (such as viscosity) thus follow the sequence Li - Na - K, whereas the properties that increase with the loosening of the structure (such as thermal expansion) follow the opposite sequence K Na Li."

" Lithium raw materials generally improve the melting properties of glasses, which is a result of the low melting point of Lithium compounds, of the formation of eutectics and the mobility of the lithium ion."

" The lithium ion resembles in some respects a proton, which has the ability to penetrate deeply into the electron envelope of anions and neutral molecules. In this way, Fajans and Kreidl explain the outstanding efficiency of Li as a flux and its effect on decreasing the viscosity, in spite of it not being an element with a high deformability of its ion. The meltability is likewise contributed to by the great mobility of the small Li ion."

Pete VanderLaan
03-31-2005, 11:49 AM
Durk: I understand what you are saying but my understanding of the story is somewhat different in that Klaus got tagged with an overhead photograaph showing clearly a cone emanating from the shop that literally showed death and destuction of vegetation that focused in his yard.

The thing that bothers me about what you say is the incredible variation in L.E.C. in the stick and my best understanding is that it persists to this day. I specifically refer to the soda lime based sticks of bright yellows and red opaques which the last time I measured them were actually about an 85. This would be a group of rod that virtually fits nothing and I have to question why it would be produced if it could actually be controlled. Since most of the lead flourides run around an 89 and the transparants a 94-94.5, what is the possible motivation in not at least standardizing the L.E.C.'s when it is not difficult to do. Lining up the viscosities is another and more substantial problem ( tip of the hat to Lani here)? So my assertion that they have been- at least in the past, stuck with a premixed leaded batch that they added colorants to and that explained the wandering L.E.C.'s I would assume that the lead fluoride batch is a different base formula but I don't know that and the soda lime base for the cadmium selenium glasses has to be a diferent formula. The formula for the lead arsenates could be a simple addition of Arsenic, but I doubt it.

But making glasses that fit nothing continues to baffle me.

Lani, I understand what you are saying and understand the point to which you refer but I do normally look at the range in which annealing can and does take place at varing speeds. We certainly also agree that thickness changes everything. I would note that the 918 falls exactly in the middle of what I suggested the range to be. Once we get out in the field, we find that the equipment is a hell of a lot looser than we would like to see it be while at the same time, the opinions about what is wrong today are wide, varied and unsubstantiated. Even while you refer to the annealing point as 918, I am almost positive that Tom has referrenced 895 as an annealing point at some time in the not too distant past. I assume that would be the lower point.

With my own work on the cut glass pieces- and you saw one when I was up in Portland in 2003, those pieces cannot go into a lehr at 940, let alone 918. I need to put them in at 995 for about an hour and then to lower them slowly to 945 or they simply crack when I do the knife edged grinding that they require.. That says to me that there is something going on in annealing land which I cannot account for except empirically. I trust my controllers and thermocouples.

Dilatometry was also approached back in the '80's by Steve Maslach as well who did a GAS presentation on it as well. I did not ever see the presentation but I did read about it and Steve was really jumping thru hoops to make sure the sample didn't drag on the side of the sample tube. When I asked him about the presentation, he didn't want to talk about it. Now, I have never had any of those problems. I do not think the dilatometer is a holy grail at all. still really only trust the ring test as a final arbiter but the dilatometer gets me right into the ballpark and tells me if I am high or low. If the ring test, or the trident seal is off by much, the sample doesn't survive the test and the information is fairly useless. The trident seal is way more sensitive to self destructing than the ring is which is why I prefer the ring.

I think that Steve O'Day is correct about Theresa at C R LOO being the first to make comparison charts which told everyone about the expansion factor of each glass. I think that really came out as the number of players in the sales field expanded exponentially in the late '80's and a lot of people were just randomly throwing colors together and then happily blaming the vendors when things cracked ( what else is new?).

To simplify for me I have to say that the rules for fit are simply different in blown, cast and slumped ware. People do such bizarre things with the product that creating a homogenous rule of thumb leads me down the path of madness.

Durk Valkema
03-31-2005, 12:07 PM
You mention AP, great but at Log ç 13.4 ?
At Leerdam the batch calc program spitted out Log ç 2 down to 7 and Log ç 13.4 as AP
Philips mentions Log ç 12.4 Pa.s as AP and 13.5 as SP. The area in between is regarded annealing range in their info.
GLASMA through Glafo talks about transformation temperature at Log ç 13 in Pa.s
So what's the consensus here?

Douglas Terry
03-31-2005, 12:40 PM
This is a GREAT thread. THANK YOU ALL. Doug Terry

Lani McGregor
03-31-2005, 12:57 PM
Originally posted by Durk Valkema
You mention AP, great but at Log ç 13.4 ?
At Leerdam the batch calc program spitted out Log ç 2 down to 7 and Log ç 13.4 as AP
Philips mentions Log ç 12.4 Pa.s as AP and 13.5 as SP. The area in between is regarded annealing range in their info.
GLASMA through Glafo talks about transformation temperature at Log ç 13 in Pa.s
So what's the consensus here?

Durk, I'm not sure whether your question is directed at me, Pete or Tom, but the Bullseye annealing points that I provided earlier are at log 13.0. These are measured (not calculated) according to the ASTM test C336.71: "Standard Test Method for Annealing Point and Strain Point of Glass by Fiber Elongation".

We believe that this is Woolley's basis also, but you'd need to ask Tom, or check Frank's book (anyone?) where we think this is published. It's pretty standard in the US.

Pete VanderLaan
03-31-2005, 01:08 PM
Originally posted by Lani McGregor


I'd wager that any colored glasses that fit that base clear (i.e. show little stress in a ring, pull, Trident seal or BE chip/bar test) but have a much lower AP (such as a lead glass would) will NOT have a 94-95 COE. Their measured LEC (0-300C) will be lower.

**********************
The spreadsheet I run brings SP87 in at a 94.6 and measures with dilatometry as a 95.9. When I use that spreadsheet on fluorine glasses at 6-7 percent, I bring in a calculated expansion of 72.3 and they almost always fit the first time. I do not know the assumptions in the program being made about the fluorine that makes this so low. They also measure 95.9-96.0. It is also the case that a pulled thread of those glasses has a serious arc. I am no where near the program right now so I cannot say about the annealing Log.

I do know that opal lead fluorides from kugler have ( or at least had the last time I tested) an expansion coefficient of about 89 . They however do not fit SP87 at all. It is why Tom created SP83 which I always thought had a measured L.E.C. of about 90.5 That would be within the 1.5 ten thousandths tolerance that has been accepted in the past as the maximum outside tolerance for expansion coefficient fit. .

I am confused though about the viscosity issue. Any Kugler rod will really run on the surface of a piece made with most commercial clear glasses indicating a lower viscosity than the host clear. This could be , either cullets or batches. One of the main reasons people really liked my black as an example was firstly the density of the color but also the fact that it does not bleed at all and stays absolutely where you put it. . It measures a 96.0 but has a close viscosity match to SP87 and still contains a substantial amount of lead.. It presents no strain in a ring test at all. I find bringing all of the gut features of a glass body to be very contradictory especially when one is trying to match up radically different formulations. I am thinking out loud here and will probably get an earful from someone.

Kevin Bethea
03-31-2005, 02:33 PM
So where does The Littleton Point come in? I was reading the interview from the oral history for Harvey K. Littleton and it mentions his father coming up with it but doesn't really date it. http://www.aaa.si.edu/oralhist/little01.htm

MR. LITTLETON: And so it was his job to get rid of the dark of the moon as a factor in making glass, among many other things. He defined annealing, the softening point of glass, which became an international standard.

MS. BYRD: The Littleton Point.

MR. LITTLETON: The Littleton Point, one way of determining what is a glass and differentiating one glass from another. There are literally an infinite number of glass compositions possible. And so, it's difficult to say precisely what one glass is without some kind of comparison to another glass.

A quick google tells me that it measured the softening point to compare glasses but I was just wondering how that fit in the whole picture. sounds like viscosity being measured to me but what do I know? This has been a cool thread.
Thanks!
Kevin Bethea

Pete VanderLaan
03-31-2005, 04:32 PM
I had no idea that Harvey started Paoli Clay. Thanks for posting that. It takes quite a long time to read but it's really engrossing.

Dave Bross
03-31-2005, 06:45 PM
Yes indeed! A must read. I love his take on art.

Now, from Scholes "Modern Glass Practice":

"The softening point of a glass, defined by Littleton as the temperature at which a filament of glass of specified diameter and length, heated at a given rate, elongates under its own weight one millimeter per minute, is a definite physical quality. According to Lillie, the viscosity at the Littleton softening point is 4.5 x 10 to the seventh power poises, or log n = 7.65.

The Littleton method is illustrated on this page. The small electric furnace contains a vertical iron core, four inches in length and one inch in diameter, with a 1/4 inch hole drilled through it lengthwise and another small hole drilled two inches deep paralell to the central hole. This permits the insertion of a thermo element at a point opposite the center of the rod to be tested. The specimen is a round filament of glass, .50 to .75 mm diameter, varying not more than .05 throughout its length of 22.8 cm. This is suspended in the central hole in the core of the furnace with its projecting lower end opposite a scale ( my note: "scale" meaning a ruler), against which the length of the freely suspended filament can be observed. Length in mm is plotted against time in minutes in the same units, and when the slope of the resulting curve reaches 45 degrees the temperature at the observed time is accepted as the softening point. The softening point of a glass runs about 200 degrees higher than its annealing temperature. The range for the commercial glasses is from 500 to 800 Centigrade (900 to 1500 farenheit) ."

Lani McGregor
03-31-2005, 07:13 PM
For those suffering from “log” jam (like me), Morey mentions that Littleton initially chose the term “softening point” to describe the viscosity at which tubing bent in the flame of a lampworker’s torch.

04-01-2005, 12:22 AM
Dave, great info on lithium. Another book I'll have to find I guess (Volk). Interesting that the small ion actually makes the glass more dense and more fluxed. Good to have an actual reference rather than what I think I remember someone saying one time. ("Don't trust half of what you think!" and maybe less of what you remember!)
As a side, I always liked my batch formulas with a percentage of magnesium from dolomite better than straight calcium. Interesting to see this compared to lithium. Magnesium containing batches seemed more even in their softening than with calcium only, which makes glass harder on the cold end and softer on the hot end. Some high calcium glasses have seemed rather sudden in softening when heating.
Nick was a smart man. It seems he included lots of non-essential but very desirable components in the SP batch. Zinc for colorant solubility, lithium for durability, density, and ease of melting, a small amount of fluorine which helps with the phosphate opals.

Lani McGregor
04-01-2005, 02:01 PM
My question at the start of this thread was “When/where did COE come to be synonymous with compatibility in the studio glass scene?”

I could have spared everyone the pain (ok, so some of you like pain) of English & Turner, Winkelman & Schott etc if I’d written MEASURED, not calculated, COE – since it is the measured COE that is nowadays claimed and generally understood to equate to the “fit” of different glasses. And – no arguments here? – we arrive at this COE (0-300C, or 25-300C, or 17-300C!) measurement via a laboratory test using a dilatometer.

Where do we find this – that the measured COE equates to compatibility - in the technical literature? Is there any mention in Scholes, Morey, Volf? If so, can someone direct me to it? We can’t find it.

Was matching COEs to determine compatibility EVER the practice of glass factories in the US or Europe? Not to our knowledge. We, and everyone else we know (thanks to Durk & David Hopper for input on the Europeans; thank you, Tom, for the notes on SPB history), have been doing compatibility testing based on thread tests, ring tests, Trident seal tests, bar tests, and chip/bar tests. None of those tests are measurements of COE or LEC.

Where the COE = compatibility thing IS found is in the book that Dan & Boyce wrote in 1983, while they still thought that matching COEs – or being fairly close – was critical to compatibility. They had reservations at that time and expressed them with disclaimers like “Coefficient of expansion numbers should be regarded as starting points from which to experiment rather than definitive numbers not to be questioned” and “…some glasses that have the same coefficient number, as determined by a laboratory, do not always fit each other when fused together.” (pg. 42, Glass Fusing Book One, 1983)

But in spite of those disclaimers, our industry (colored glass dealers and other manufacturers, and eventually users) grabbed this easy “code” and started using it to define compatibility. Terms like “Tested Compatible to 90.0” (even though the experts will tell you that you can’t even measure to a .0 of accuracy in a dilatometric test) and “90 COE glass” came to be accepted to mean “this glass will fit other glasses of this same COE”.

When Bullseye published its actual COEs that showed a COE (0-300C) range of 88 for our white and 91 for our clear, it was interpreted to mean that we allowed a mismatch of plus or minus 1.5 COE points. We never said that (but this also seems to have come down in the lore - note Pete's comment earlier).

When we declined to guarantee that our glasses would fit other glasses with a COE of “90” we were accused of trying to corner the market and refusing to be “cooperative” with other manufacturers.

The ball was rolling. Dealers were looking for easy ways to inventory, categorize and sell. (I remember the work that Therese did at C & R Loo to try to categorize compatible glasses. It was a supremely noble effort. But I can guarantee that she didn’t have COE tests run on those glasses. At $150 per sample, does anyone really think that Mr Loo let her spend that kind of money to find out what the COE of K61 was, much less the entire Kugler line? I suspect she called around and ASKED. If she then put COE numbers on the answers, it was pure speculation and trust in her sources.)

(apparently I’ve exceeded the ability of the blather-o-meter to track my rant at this point, so this is continued in the next post…)

Lani McGregor
04-01-2005, 02:03 PM
I originally asked this question (started in the prior post) because I honestly don’t know for sure whether Glass Fusing Book One is the original source of this bad science. But from what I’m reading on this board, this (early 1980s in the fusing sector) is where the measured COE as a synonym for compatibility first showed up in studio glass.

I would LOVE for someone to find evidence to the contrary, because we’d really like to blame all this crap on someone else. I can’t find it.

Now it’s everywhere. It’s accepted as “biblical” even though it runs counter to users’ own experience.

This is what amazes me here in the Kingdom of Blowing: I can understand why kilnworkers have a hard time understanding viscosity and how it is an equally important factor in compatibility. We put stuff in a box, turn on the heat, close the door and usually don’t have a clue what happens until we open the door and it’s broken or not. Pete, why do you say that blowers’ eyes “glaze over” at the mention of viscosity? Who the hell can’t feel/see the difference between a hard and a soft glass? Why would any blower think that the most OBVIOUS characteristic of a hot glass would not be at least as important as the characteristic he can’t even experience (the expansion between 0-300C)???

Contrary to what we’ve been accused of (thank god you’ve banned David from this board or I’d never have gotten this far), Bullseye is not out to BASH the COE. Jeeezus, how sick does that make us? What next? Do we go mug a Tg? We’re only arguing that divorcing it from viscosity seriously hinders the understanding of what makes glasses fit.

But I never intended this to be an “argument” anyway. I was just hunting for evidence that Bullseye didn’t start this COE = Compatibility mess in the first place. So far, I haven’t found any.


--------

Steven O'Day
04-01-2005, 02:45 PM
Lani- I am pretty sure that Therese had the base glasses tested, but agree that they probably used the manufacturer's numbers for the color.

I was at Bendheim at the time and the two main problems were bad quality color and compatability problems. It seemed like some bars had more stones than glass.

Some customers were screaming for guidance on compatability. We had a lot of personal experience and anectodal help but no empirical proof. And so the COE number. I don't think that anyone ever represented it at the time as the end all, but a starting point. We always recomended testing with the actual base glass being used.

We were familiar with Boyce and Dan's book and had been around workshops that Boyce did in the early 80's. This was one source, I was also looking at Scholes. I believe Huchthausen had a lecture on it at Appalachian Craft and I remeber that lecture that Maslach gave. I don't remeber a eureka moment but rather a whole lot of sources saying the same thing.



Did that information travel with the bars? Does anyone who used Kugler in the '70s or '80s remember these ratings?

Yes, Kugler had the words Harte W on the labels but no numbers. They also seemed to be color coded (the labels) but I assumed it had to do with the color of the bar. And the glue was water soluable so it was easy to get the label off!

Lani McGregor
04-01-2005, 03:43 PM
Originally posted by Steven O'Day
Lani- I am pretty sure that Therese had the base glasses tested, ...

But what were the "base glasses"? And I'd still be shocked if Mr Loo OK'd dilatometric lab tests, considering the expense.

Some customers were screaming for guidance on compatability.

I remember the pain.

We had a lot of personal experience and anectodal help but no empirical proof. And so the COE number. I don't think that anyone ever represented it at the time as the end all, but a starting point. We always recomended testing with the actual base glass being used.

I believe you. Nevertheless, the information has morphed over the years from "if it has the same COE it's (probably) compatible" to "if it's compatible it must have the same COE". Hence, people in Germany are fusing Bullseye (that famous "90" glass) to Desag Artista and because most of it isn't cracking wildly, dealers are listing Desag as a "90" glass - contrary to what the manufacture lists as their measured COE (which Desag lists as 94)

We were familiar with Boyce and Dan's book and had been around workshops that Boyce did in the early 80's. This was one source, I was also looking at Scholes.

Did you ever find any reference in Scholes that equates a measured COE with compatibility?

I believe Huchthausen had a lecture on it at Appalachian Craft and I remeber that lecture that Maslach gave. I don't remeber a eureka moment but rather a whole lot of sources saying the same thing.

But what exactly was that "same thing"?

Thanks for the input. It's great to hear from someone who was at Bendheim back then. I sure wish I'd held on to catalogs! I just KNEW that cleaning house we fundamentally WRONG .

Peter Bowles
04-02-2005, 04:21 AM
[QUOTE]Originally posted by Lani McGregor
My question at the start of this thread was [B]“When/where did COE come to be synonymous with compatibility in the studio glass scene?”



Its probably more to do with the technology that the potters and ceramicists brought with them when they moved over to working with glass than something that has been promulgated by the glass industries.

Certainly from a UK perspective, many of the key educators in glass have come from a background in ceramics, and with an understanding of 'fit' and 'compatibility' between ceramic bodies and glazes as an integral part of their knowledge and practice. Ceramic glazes are almost always made to fit by shifting the COE- a little bit more or less Silica will solve most glaze fit problems. I reckon some of this same thinking has just been transposed onto the 'new' materials of glass and taught into the system.

Marc Leva
04-02-2005, 10:51 AM
Originally posted by Lani McGregor
I originally asked this question (started in the prior post) because I honestly don’t know for sure whether Glass Fusing Book One is the original source of this bad science. But from what I’m reading on this board, this (early 1980s in the fusing sector) is where the measured COE as a synonym for compatibility first showed up in studio glass.
--
Glassforming;glassmaking for the craftsman by Frederic and Lilli Schuler ©1970 pp.97-98
"When glasses are mixed, it is important that they have the same coefficients of expansion, so that stress is not set up at the interfaces between the different glasses after cooling."

Tom Littleton
04-02-2005, 11:08 AM
OK
I asked HKL if he ever talked about COE in his seminar. He said that he did not. He indicated he did know about caculating COE even before he got into glass but seemed to have considered it superfluous. He said he used the empirical (trial and error) approach and knew about making things "fit" from his years as a potter before he got into glass.

An interesting aside is that he did say that he knew both Scholes and Green and that Green had lived in Corning and had worked for his father (J T Littleton) at Corning. Also some years ago HKL told me that he used to play poker with Labino in Toledo when he taught at the Toledo Museum. That would have been in 1950 and 1951 before he moved to Wisc.

I asked when he first knew about Kugler and he said he visited Herr Kugler in Olenburg sp? before he moved to Kaubeuren-Neugablonz but couldn't say what year.

The Wooley data is from his book "Glass Technology for the Studio". I believe that the tests were done in the Corning Labs.

Just to confuse the issues
From Robert Stephen in 1996 come these results (done at Corning Experimental Labratories I believe). These tests were done to the ASTM C336 standard. Annealing Point-499 degrees C (930 degrees F) and Strain Point-461 degrees C (861 degrees F)

We originally got an 890 annealing point from Nick Labino and that is what we put in our literature.

Anybody who asks me about annealing point and annealing gets a whole "song and dance". I tell about how inaccurate thermocouples can be. I then tell them to calibate their annealers using the sag test and mention Henry's book (so that I can tell him how I'm promoting him and stay on his good side). I also mention the need for some kind of polariscope to check for strain.

Some of you may remember the old Wiesenthal sp?. It had the expansions printed on the bars. The first stuff that was availible was just under a 100 COE.

Steven O'Day
04-02-2005, 11:47 AM
Peter - I agree, expansion was widley taught in the ceramics programs at the time.

Lani - My recolection is this: I worked at Bendheim for a short while and went back to studio work. Therese was at CR Loo and I distinctly remember having conversations with her about them testing some clear glasses and how expensive it was and being surprised how far off the tested numbers were from the calculated. I don't have the catalogs either, but the glasses probably were Gabbert/Louise, SP and maybe East Bay (though this may have come latter). I think there was a Schott in there too.

I don't remember any specific reference in Scholes and am not inclined to go looking having had a hard enough time with it the first time.
But what exactly was that "same thing"?
When the question of fit came up in a workshop the only thing I remember being discussed was expansion. There always was talk about how even if the expansion was the same, sometimes the glasses would still not fit. You are correct in stateing that glassblowers should have known about viscosity being a factor and of course we did, having to deal with it in every piece that has two different types of glass. But no one that I know of knew how to measure it.

My working strategy was to ask around about color fit first. Pull a cane test, if it was way off return the color. Fuse some chips to a rondel and look at through the polariscope, if way off return the color. Maybe make a paperweight with the color and a lot of crystal and look at that. I would sometimes do the ring test, mainly if I wanted to show off. I think this was more testing than a lot of studios did, but not as much as some.
fusing Bullseye (that famous "90" glass) to Desag Artista and because most of it isn't cracking wildly, dealers are listing Desag as a "90" glass - contrary to what the manufacture lists as their measured COE
Copy writers, the bane of truth everywhere.

I doubt that you will ever get a definitive answer to your question.

Lani McGregor
04-02-2005, 12:38 PM
Originally posted by Tom Littleton
From Robert Stephen in 1996 come these results (done at Corning Experimental Labratories I believe). These tests were done to the ASTM C336 standard. Annealing Point-499 degrees C (930 degrees F) and Strain Point-461 degrees C (861 degrees F)

Tom, thanks for this! Great info
Why were these tests done?

Was a COE measured at this time? If not, why not?

Did Robert's tests pre-date Woolley's?

Lani McGregor
04-02-2005, 12:45 PM
Originally posted by Marc Leva
Glassforming;glassmaking for the craftsman by Frederic and Lilli Schuler ©1970 pp.97-98
"When glasses are mixed, it is important that they have the same coefficients of expansion, so that stress is not set up at the interfaces between the different glasses after cooling."

Well, thank GOD!

But who were the Schulers? Flameworkers?

Again, I think this is "popular" science (with its typical half-truth).

Does the book mention what glasses they were mixing?

Lani McGregor
04-02-2005, 12:56 PM
Originally posted by Steven O'Day
You are correct in stateing that glassblowers should have known about viscosity being a factor and of course we did, having to deal with it in every piece that has two different types of glass. But no one that I know of knew how to measure it.

But you DID know, you just didn't know you knew:

... Pull a cane test... Fuse some chips to a rondel and look at through the polariscope.... Maybe make a paperweight with the color and a lot of crystal and look at that. ...do the ring test,

These are all tests that measure the combined results of COE & viscosity (you can't separate the two). None of these tests measure COE. You DID know how to measure viscosity.

Copy writers, the bane of truth everywhere.

amen

I doubt that you will ever get a definitive answer to your question.

I don't need a definitive answer. I'm just looking for extenuating circumstances to get my husband's sentence reduced for aiding and abetting Bad Glass Science.

Marc Leva
04-02-2005, 01:31 PM
Here's my convoluted theory.

Dr. Schuler (Ph.D U Wisconsin'49) was senior research associate of the Fundamental Chemistry Group, Corning Glass Works from '53-'56 and administrator of the Scientific Research Program, Corning Museum of Glass from '56-'58. While with the museum he met F. Carder and had a chance to work on casting in his workshop. His wife also worked at Corning in a scientific capacity.(from the dust cover)
He did other types of art (drawing, clay, etc.) for several years and the started doing flamework in '67 which led to him writing a book on flameworking. Then he started doing casting again. Also in '67 at Corning 2 large cast disc were made. 1 - 157 inches dia. X 25 inches thick, 1 - 144 inches dia. X 20 inches thick. The first weighed 18 tons; the second , about 12 3/4 tons. They made them from smaller pieces of glassy (not crystalline) silica that were preshaped, arranged in the mold and fused together. Glassy silica was used, among other qualities, for its low expansion. Its expansion is 4 and I think the Palomar was boro at about 30.
The book has many qualifiers when it talks about COE. Its mostly in the context of enameling on glass or casting. It also has charts and grafts and comparisons of all kinds of different things until it starts to take on a bibilical effect. If you take a passage from the front and pair it with an unrelated graph in the appendicies and then confirm it with a paragraph from the back on a different technique, well hell, things start to make a weird kind of sense. Different qualities take on strange proportions. And I think for Schuler, at least, he was impressed with the whole glassy silica lenses low COE and its in his book alot.
Living down here 240 miles south of bum****, I didn't get this book until it was recommended to me by James Broadwell at Ruthglass. That was in '81. There just wasn't any information for casters and this was an incredibly helpful book. I don't know when David Ruth started making glass but the book was there in '70 and Schuler was living in Santa Barbara, Ca.
Just a guess.

Lani McGregor
04-02-2005, 02:31 PM
Marc, Oh good, Mr & Mrs Schuler weren’t bongmakers by trade. Whew!

But the earlier statement "When glasses are mixed, it is important that they have the same coefficients of expansion, so that stress is not set up at the interfaces between the different glasses after cooling" is still without enough qualifiers to be applicable to all studio glass situations.

Primary missing info here is:

1. What glass were the Schuler’s working? Were they mixing glasses with the same annealing points (i.e., the same viscosity)? If so, the statement is undeniably true.

2. Does Schuler mention which COE he’s talking about? 0-300C? Or a COE for instance in the 500-530C range?


So much of the problem today, as has come up earlier in this thread, is with the mixing of color where the viscosities – which are indicated by the AP - are often so different. Finding any reference in the technical literature to compatibility issues in mixing colored glasses of different base compositions is close to impossible.

The other problem with part of this discussion is a semantic one: the mismatch of glasses is commonly referred to as an “expansion” problem, but the term “expansion” used this way refers to the strain between the glass, NOT to the LEC of either or both glasses. This expansion difference (or strain) is not solely the result of LEC differences.

L.

PS. Marc, I don't mean for you to have to spend your Saturday copying passages out of this (great reference, thanks!) book. I'll go track it down and add it to our library....

Marc Leva
04-02-2005, 03:40 PM
The book is not really technical. I does have charts and graph and tables but they don't all have the same information. It has a graph of viscousity coefficient verses temps for "several" glasses against "ordinary material (300C-1000-1200C), next page the same for Corning Code 8391, PPG Pennvernon and LOF Colburn glasses. Then a table with COE of fused silica, boro and soda-lime glass. Then a graph showing a generalized expansion of glass colors with a substrate glass that ranges from 0C to 510C. Individually they don't mean much. But if you mix and match the info anything is possible. I didn't mean to deflect the origins towards Schuler or David. I'm just saying that the book was on the W coast and so was Schuler. If your a young guy wanting to make sheet glass, like several people were attempting at the time, wouldn't you ask around? If some guy who'd worked at Corning was available wouldn't somebody talk to him?

But the earlier statement "When glasses are mixed, it is important that they have the same coefficients of expansion, so that stress is not set up at the interfaces between the different glasses after cooling" is still without enough qualifiers to be applicable to all studio glass situations.

Thats the only sentence in the whole book that doesn't have qualifiers within the sentence. And it actually refers to striae in a clear glass body.

I should be working on my taxes. I'm just working down my procrastination list. I had a very small triumph in the studio yesterday and I'm not set up for any failures till tomorrow so, I'm staying out of there to bask briefly. Its this or taxes respond faster, please!

04-03-2005, 07:04 AM
OMG!! Total Flasback!


Waay back I did Stained Glass and the Ruth Glass -End of Day sheet glass was Totally AWESOME..amazing colors the glass cut like butter.. !!

I went into my secret stash and found I still had several End of Day Ruth Glass Sheets !! yippee!! I had forgotten about them !!


In 1980 Tony Parker came up to Alaska and did a fusing glass workshop.. that was my first exposure to fusing and the first time I heard of COE..
followed by Doug Hansen, (fuser and caster ! ) Ruth Brockman Richard LaLonde,Liz Mapelli , Boyce , (your little buddie..just loved when he pitched his dinner fork at Cathy during dinner... thank G-d his aim sucked ! ) they were all big into teaching compatibality..expansion and COE ..and "TOUTING" B/E Tested Compatible Glass!

my first exposure to issues of COE and "fit" was with fusing and Bulleseye. Glass.. Looks like yur company may be guilty after all Lani.. of "spreading the word" in the 80's Fusng Book# I was a "bible" / manual / guide to fusing.. original book had graphs and charts on testing.. and COE.. !! Followed by Gil Reynolds book..

Therez at CR Loo did do COE charts.. ( I hate to clean !!) and then they were picked up by OCR in their catalog..

Bad Science or not.. seems that Bulleseye Tested Compatible put the concept of COE 'out there' in a huge way.. and it is still out there.. sorta like a Jeannie outta the bottle...too late to put the cork in it.. and yu want to put the cork in the bottle why??


mmmm.. seems that COMPRESSION and TENSION HAVE NOT been mentioned in this discussion, and they are very important to the way a 'blower" uses color bars and base clear!



Cynthia

PS
someone check my memory. on this...

was not the "standard" base glass , for blowers, back in the 80"s, and early 90's Louie cullett??
I seem to remember 'everyone 'used Louie until the day that Louie "changed " their formula and forgot to tell their customers!! and all hell broke loose.. glassblowers lost huge amounts of work as it sat in the shelfs..glass just blew/flew apart!

was this not the time when Spruce Pine Batch took hold among glassblowers in a large way?

Lani McGregor
04-03-2005, 01:08 PM
Originally posted by CynthiaEngland

… they were all big into teaching compatibality..expansion and COE ..and "TOUTING" B/E Tested Compatible Glass! … my first exposure to issues of COE and "fit" was with fusing and Bulleseye...

I’d agree. “Touting B/E”. Boyce was a Salesman and COE = compatibility certainly made fusing easier to grasp for the hobby market. And “easy” is more saleable. But that doesn’t make it correct. But Boyce left Bullseye 20 years ago. And in spite of all the qualifiers that Dan tried to put into GFB1, the demon-child of COE & Compatibility lives on.

Looks like yur company may be guilty after all Lani.. of "spreading the word" in the 80's Fusng Book# I was a "bible" / manual / guide to fusing.. original book had graphs and charts on testing.. and COE.. !!

Yes, but read the qualifiers in that book about how glasses with the same COE may not fit and how COE is only a “starting point”. Seems like our entire market just zipped over that. How come people weren’t screaming “why not?” IMO, because it’s easier to SELL if it’s SIMPLE. Screw ACCURATE.

Therez at CR Loo did do COE charts… and then they were picked up by OCR in their catalog..

We still don’t seem to know HOW Therese came up with her numbers. But you just gave me another piece of the puzzle. I’d wondered where OCR got the numbers on their charts. They are interesting:

http://glasscolor.com/colors/coefficient_table.aspx

How come there’s no “Measured COE” for Gaffer on that chart?

Why, instead, is there this statement from Croucher:

“Gaffer Color range will show very little retardation and thus very little measurable strain, when fused to a typical soda lime glass that measures at 96 x 10-7 (20-300C) and has an annealing range between 450-520C (840-970F).” -John Croucher

Because Croucher knows full well that a COE without the qualifier of viscosity can be very misleading information. So he suggests the viscosities (annealing points) AND the additional qualifier “typical soda-lime glass” needed for the COE to work.

And the other data, according to you, was just lifted off the C & R Loo charts. Well, that information (“90 COE”) is wrong for Bullseye. Why should anyone think it’s right for the other color makers?

Bad Science or not.. seems that Bulleseye Tested Compatible put the concept of COE 'out there' in a huge way.. and it is still out there.. sorta like a Jeannie outta the bottle...too late to put the cork in it.. and yu want to put the cork in the bottle why??

We just want to let the “Jeannie” of viscosity OUT of the bottle and clear up some of the rampant – and increasingly problematic – half-truths that the Salesmen (yes, Boyce was one of the pioneers) have brought into studio glass. This industry – I guess it’s a sign of growth – has gotten rampant with Salesmen. And the users seem perfectly content to accept marketing as technical information.

I may be hyper-sensitive on this issue – having been bashed for years by David W. who believes that every piece of technical data that comes out of Bullseye is a sinister PLOT to control the market – but why would you even ask why we want to “put the cork in the bottle”?

OK, truth is , we’re drilling for Viscosity in the Arctic National Wildlife Refuge and if we can convince the studio glass community that it’s got value, VISCO-BULL, LLC. is gonna make us richer than King Fahd.

Shit, Cynthia, I knew it would take a blond to figure it out.

Pete VanderLaan
04-03-2005, 01:45 PM
jeez, I just had to get away from this and do something fun, SO I just did an alchohol intervention, flying from Santa Fe to Denver to LA to Denver and back to Santa Fe in 24 hours. On the way back, I sat next to a valley girl who watched MTV , giggled incessantly and who keep applying a lip gloss that smelled exactly like the little cake in a men's urinal.

Anyway, I did some testing for CR LOO but it wasn't that far back.. I think I did it in about 1996 or whenever Croucher was bringing Gaffer into the market. I do recall asking for formulations on various glasses and getting most of them with the exception of GLASMA who would only supply a stupid pie chart that was useless. My recollection of Theresa's efforts was that she simply collated the responses from various manufacturers. and believed them. ( I mean crap, she believed me,)

I don't have the article right in front of me but my distinct recollection of the 1.5 ten thousandths difference was mentioned specifically in Manner's article.

If you really think about it Paul could take the blame for all of this and get Dan off of his invisible hook, especially since none of us know where Paul is: His article only talked about expansion and never about viscosity as being an issue.

When I say "mention viscosity and eyes glaze over", They do. I wish they didn't but they do. Glassblowers by and large really take no responsibility at all for their materials.They want to be told "It fits" which is essentially what Bullseye tells them. When I mention that the expansion of a certain clear glass being imported wanders all of the time when I test it, I suspect that the viscosity does too, I have no motivation to check it. Even so, glassblowers buy the stuff by the ton and scoff at problems until they inexplicably have them and then it's almost always someone elses fault.. With many of the clear cullets, they are not designed for handblowing but are designed to go thru gob feeders and never have to be mated to another glass type. They were never intended to be used in small shops or matched to "Isotoner" color rods. People want to be lulled into complacency and they really really want to believe that weight gain isn't their fault and that you can lose weight sitting on the couch eating Pizza if you just take Cortisol. Eyes glaze over because being responsible involves real work.

I actually think people would be happier with Heidi Broderbund's 15 percent rule that the beadmakers used to hold up as the first of the ten commandments. Grrr....

The part of the puzzle that never gets answered for me is why German color rods, with their 45 percent lead and their clearly wildly different viscosities will fit ( meaning they don't actually explode) the bulk of clear glasses marketed today in blownware. The expansions aren't far off but the viscosities are and you can visibly see it in the bleeding that occurs when any german stick is applied to the surface of ant clear glass. It's like an ink stain on a white carpet. It fails when you saw it so guess what? People don't saw it and say it fits. Would you stand under a chandelier made with Spruce pine and Kugler's bright yellow opaque? I wouldn't. ( and I know it's not a lead rod.)

04-03-2005, 05:48 PM
Being only interested in confusion rather than in answering Lani's question, I want to add a question to the viscosity discussion. Why does anyone think that measuring viscosity in the 17 to 300C range tells the story of what happens over the entire annealing range? Do all glasses remain linear above that temp up to their annealing point? And isn't a 40 or 50 degree difference in annealing points (or strain points) sufficient to create a fairly large difference in the total contraction that each glass experiences? I favor the behavioral tests over the theoretical because all of the factors that we can or can't measure are included. The ball test is one that no one has mentioned. Take your color and gather a clear layer over it. Shape and anneal. Observe cracking if any. Look at through a polariscope. Most problems will show up at this point. If you want lots more evidence or reassurance do the following. Saw it in half. Observe. Saw a slice. Observe. Look at through a polariscope again. Polish one face (this micro-heating can set off latent strain). If there are problems, compare to a pull test tt determine what the problem is. I think Lani hit one thing right on the head. There is skill in doing a good pull test and they should be repeatable. And there are limits to what they mean, but a dilitometer test of expansion over the lower and of the cooling range doesn't tell the whole story either.

Pete VanderLaan
04-03-2005, 06:36 PM
well, the curiosity I run into, and I agree that neither a pull test or a dilatometer test tell the definitive story BUT when I do a ring test and I get a slight gap, it tells me that the inner glass needs a higher expansion. If in 100 lbs of the inner glass, I add about 100 grams of sodium, or another of the alkaline fluxes, the gap usually closes. That is true in either opaques or in transparants. What it doesn't say as a test again applies to viscosity and it is grossly obvious that the viscosity of a soda lime clear is way way higher than it is in a fluorine opal. My opals actually melt at about 1975-2000F which really tells the viscosity difference in a heartbeat. Now I can get these two totally dissimilar glasses to do great in a ring test, to give me a consistent readout in a dilatometer, give me terrible pull tests have totally different softening point but saw like a dream and grind like a dream, never break in blownware, but check if there is too much of the opaque in relation to the transparant soda lime present. That is as in 2 inches thick or so. At one point I was making some weights that were about four inches across. I would take two big gathers of the fluorine cased in clear and they would crack. If I used a gather of clear, then the fluorine and then the clear, they were perfect and never gave any trouble. If I blew those glasses together, they never gavwe me any trouble. I could grind and I could saw and they never gave me any trouble. I varied annealing schedules and it never affected a thing. I don't know what the deal was.

Now I know that the fluorine crystals are growing, collapsing and regrowing as the glass ages but it's viscosity doesn't seem empirically to be changing much. I suppose I could continually check it each day for differences, I just never have. I am simply observing that as the density of the opacity goes away, the viscosity doesn't seem to go along with the density loss.. When I make color rod or frit, I capture the density of it usually about ten hours after the melt and I have not had occasion to watch its characteristics deteriorate in a measurable way/ ( nor do I care to)

Chuck Savoie used to say to me, and it really applied to cad sel opaques particularly when we were screwing with some of the old Thuringen formulas,, "Sometimes it's so far out, it's in." The information is so conflicting.

Cold comfort.

John Croucher
04-03-2005, 09:07 PM
When Gaffer was started in the early 90's the biggest headache was what expansion/viscosity standard was out there for glassblowers. Whereas the fused glass manufacturers could totally control compatibility in-house, color bar makers had to somehow fit with a myriad of clear batches around the world. In Australasia alone we were faced with 20 odd recipes with widely varying LEC's and viscosities. The Germans were no help, since their pallet was all over the map.

The other problem was what was the best test to check compatibility in-house. Industry standard dilatometers offered no better than +/- 1-2% accuracy and cost upwards of $20,000 and the info was useless unless the respective strain or set points were concerned.

I have to thank Frank Woolley at Corning for pointing us in the right direction, a direction that the fusing manufacturers had been pursuing for years. Measure the mismatch with polarised light and a trident seal. The fusers use flat glass -cane makes more sense for hot glass workers. The trident seal takes care of differing viscosities up to the respective strain points of the glasses, as well as differing Youngs modulii, emissivities, surface tensions and of course LEC's. The strain, whether in tension or compression can be read very accurately with a polarimeter. After a while the retardation can be interpreted chemically when adjusting a batch. We can look at the results and know something needs adjusting up or down by what we call LEC on our spreadsheets.

That still left the question of what to be compatible with. Looking at what was potentially our biggest market globally, there was an obvious Titanic out there -Spruce Pine 87 batch. Even though we felt it's contraction was a little high compared to most of the German glasses (we didn't want to be in our own universe) we adopted it as our standard. We then created Gaffer Batch which was compatible with SP87. That is now our standard.

We are still totally at the mercy though of peoples melting practice, length of time their clear is in a pot or tank, whether the clear batch has been mixed correctly etc. In Europe we are up against widespread use of Glasma batches which are far too high. The same goes for Japan. Vast numbers of glassblowers think a thread test tells them everything when it doesn't, unless the two glasses are very close re LEC and viscosity. It's time we caught up with the fusing scene, which had all this stuff figured out 20 odd years ago. I agree with Lani -measured COE's have become a lazy way of descibing a glasses compatibility. We are guilty of it ourselves. Unfortunately there isn't a quick way of resolving this problem, because there isn't a standard glass. If there was, then one could compare all the studio recipes to it by quoting +/- retardation variances as nanometres/centimeter

Jordan Kube
04-03-2005, 10:06 PM
So your weights were breaking because of a viscosity mismatch. While the outside set up the inside was still hot. This is how things cool down. By the time your flourine was ready to set up the clear wasn't going to give at all creating tension within the piece. Does your flourine set realy fast once it reaches a certian temperature? My thought is that the glass may be good at creating stress within itself if it's thick enough and then adding the clear over it just makes it worse. Maybe you could have slow cooled it by flashing the thing in the glory hole for ten minutes. Who's got time for that? The clear flourine clear arangement probably helps sandwich that tension a bit. I think the blown ware is structurally stronger at distributing the stress evenly throughout the piece provided that it's round. There isn't such a difference in the rate of cooling from the outside in with blown ware either. I think you gave the best example about what this is all about.

Jordan Kube
04-03-2005, 10:13 PM
Would the same shape and size weight made entirely of the flourine glass hold up to the saw?

Pete VanderLaan
04-03-2005, 11:25 PM
the term "set-up" is not a good one to use really. The dfferences here are ones of viscosity and annealing point which go hand in glove. I was simply trying to demonstrate how one can have most of their ducks in a row in most instances but there will still be exceptions that will give you trouble..

John knows that while I really respect the trident seal that I think it is so sensitive that the sample breaks very easily unless it is damn close in the first place. A lot of what I am looking for is methodology that lets a studio glassmaker analyze their process in a variety of approachable ways. The polarimeters that John uses run a couple grand and while I don't deny the accuracy of the system, I don't think many private studios are going to be willing to make that investment It is where I think the ring test is a very good indicator for not a lot of cash. I think the trident makes sense for major manuafacturers like John but I don't think it's necessary for people who want to make their own colors in house. It is really still the case that if a piece survives the diamond saw while making the ring, the piece is effectively compatible. The ring gives the very fine tuning indicators in the same sense that John's trident seal does the same, or at least that's my opinion.

As to the fusers, I think that bullseye effectively guarantees compatibility within a closed system and that makes perfect sense. Spectrum apparantly does the same thing but by calling their product system 96, the implication is there that any glass hawked as a 96 L.E.C. is going to fit right in. It won't. The fact remains though that the bulk of glasses being produced today have to acknowledge what John calls the Titannic in the room which is SP87 which I think still has a clear majority of market share in commercial batches in this country. Even if it doesn't, the other manufacturers are still shooting at 96 and their annealing points and viscosities are really not far away from Spruce Pine. If they were, we would really be hearing about compatibility issues all of the time and we aren't. The cullets are another story.

And yes the weight survives grinding and sawing just fine.

Jordan Kube
04-03-2005, 11:46 PM
<-------- is not affraid to ask stupid questions. lol

Pete VanderLaan
04-04-2005, 12:00 AM
There are very few stupid questions here Jordan but there are different levels of experience . John Croucher and Lani know tons more than I do and even so, I know a lot. It gets good when all of those experience levels come together looking for something everyone wants and can do it without a lot of ego.

Jordan Kube
04-04-2005, 12:30 AM
From what you say about your process it seems like you could get along quite well without your dilatometer. You've got a series of tests that can lead you to a conclusion about a particular color in relation to another glass. You then make adjustments based on what you see yes? So how do you quantify viscosity in a glass? Does it need to be?

04-04-2005, 12:31 AM
I think that both the ring test and trident seal are behavioral, in that they take into consideration the behavior of the glass in a process including the method of annealing used. What is hard here is that they require annealing which is hard to wait for when you have a tank of glass and color to use. I also agree that the pull test makes the most sense with the least variables, which is the case a lot of the time when adding color to batch. You have limited things to change. Who knows what the variable are when the bar formula is inknown? Survival is the test. The ring test is probably the quickest test of survival.
So Pete, what is the quickest ring test method? If the wall thickness is less that some measure, can it be cooled in say an hour or two and still be meaningful. This does not reproduce the actual annealing that might be used but gives you something to look at before lunch. Can we get down to what you call a useable methodology?

Jordan Kube
04-04-2005, 12:49 AM
When I worked for the venerable Ed Skeels he had a pretty good method. Blow a thin cylinder, anneal, score with a diamond point and watch to see if there was a gap or an overlap. Ed would measure the thickness of the cylinder and the gap or overlap with a micrometer and record the measurements. They were pretty thin and I think he annealed them pretty quick.

John Croucher
04-04-2005, 04:41 AM
Hugh, the trident seal test takes no longer than a ring test .In the case of a paper weight created for the saw test much more. Both need to be annealed, but if the samples are thin -ie around 2 mm or 1/10th of an inch or less, its all over in under 90 minutes. The trident seal advantage is that it is easier for a neophyte to get more acccurate results. Getting the ring test to have equal thicknesses of both glasses is quite difficult and equal thicknesses of both glasses are critical for an accurate outcome. The fusers all have a reasonably equal sheet glass thickness to work with.

The trident seal test allows a quiet and unhurried measurement to take place with the accuracy of a micrometer before fusing the respective glasses, whilst overlays circling around a glory hole don't. Ed Skeels or Lino or Peter V may be able to do overlay ring tests with the respective glasses thicknesses within 0.1mm of each other, but I would wager most glass blowers can't. Pete V rails against the trident seal test as being too sensitive, but in our experience it can accommodate a difference of 200nm/cm, which for most glasses is around a 4-5 point difference. That's a wide enough gap to test for and make adjustments. Some glass formulations are really peculiar. For instance, a fluorine opal glass with around a 20% PbO content is unbelievably unresponsive to react to an alkaline addition or subtraction re nm/cm. What we thought would require a chemical addition of 1-2 points LEC required an 8 point addition on our chemical spreadsheets. Some glass families adjust really rapidly to minor alkaline additions or subtractions, others require major alterations. Actually, outside of our measured clear glass parent families, I don't care what the measured LEC'c are of our 9 glass matrices are. All we care about is whether all the glasses fit each other. within an annealing range of 470oC -5202oC.

The other thing I forgot to mention in my earlier post is how critical the temperature range is when LEC measurements are concerned. Theoretical comparisons are useless when comparing English and Turners factors with Appen or when real world actual measurements are concerned. Most of the C&R Loo published results are either theoretical or voodoo nonsense. E&T worked everything out over the range 25-90oC. Appen calculated all his factors over 20-400oC. In Woolley's invaluable monograph, SP87 measured 94.9 over 0-300oC and 97.8 over 25-300oC. The E&T numbers come up at somewhere around 88-99. Quite a big difference. Corning uses a US$50,000 Theta dilatometer that has no better than +/- 1 LEC point accuracy, so even there the numbers are vague. That's why we say AROUND 96 x 10-7 over 0-300oC with our standard with an annealing temp of AROUND about 490oC . It's in the ball park but no more.

Dave Bross
04-04-2005, 10:20 AM
Along the lines of suggested simple and quick in studio "ballpark"sorts of tests, here's a little back yard/shade tree upgrade for the thread pull test that has done good things for me in helping repeatability.

I've been using approx. 1/4' wide strips of sheet glass that match the expansion (and are pretty close on viscosity because they're the same general sort of glass) of what I'm shooting for, Spectrum 96 for 96, Bullseye for 90, Moretti for 104.

With a torch, I can easily heat, apply, and flatten out with tweezers, an equal amount of the mystery glass to the glass that is below it in the strip of known expansion. From there, heat it until it balls up and pull. I shoot for the same length of pull to also help consistency. I'll also pull a thread test between the actual glasses I'll be using because even though glass A may fit glass B, and glass C will fit glass B, it doesn't mean that glass A will fit glass C for all the reasons we have been discussing in this thread.

I've got it to where with my spreadsheet results, this technique, and whatever other dark of the moon factors reside locally, I can pretty reliably say that 1mm of bend in 200 mm of thread is just about .6 to .65 in expansion in my spreadsheet, which is conveniently just about what a pound of sand (in a 100 # initial recipe) will move the expansion in a basic soda lime sort of glass. Your mileage may vary.

Final check is a homemade polariscope (two polarizing lenses from cameras, cost $20 from Ebay) used on a section of glass containing the two glasses cut from whatever application they are destined for.

I've come to know from experience how much stress will pass in which application and I'm always working to dispose of even small stresses in the next go-around. There's an article over at the warm glass board on compatibility that has pictures of a chip and bar test in various stages of stress. This was what I initially used to "calibrate" my eye as to what I was looking at in terms of stress levels.

I can't get good results with this if one of the glasses is lead. I'm trying to wean myself from lead anyway, so not terribly critical for me.

I can get pretty good results in the striking glasses if I simulate all the strikes that will happen in the course of working out the glass by reheating the sample as many times as it will strike in the particular process where it will be used, including one for the anneal.

Pete VanderLaan
04-04-2005, 12:34 PM
Jeez, I didn't think that saying I thought the trident seal was sensitive constituted "railing" but everything I've been told about it said they were easy to break.

I anneal my ring tests overnight since I am seldom in a hurry. Factory floor tests are pretty much what Skeels was doing..

I also still use my dilatometer, all of the time since it tells me where in the ballpark I am. If a ring sample or a trident seal breaks, you don't know anything. Los Alamos Labs assured me that regardless of the modest cost of my unit, that it is quite accurate when tested against their big kids toys. I would admit that when I turn it over to the inexperienced, strange things happen. I believe that Corning will also say that any tests that you do there should be performed by the same person.

Ring tests really speak to you the moment you put them in the diamond saw. 99 times out of 100, if you saw it, it breaks right away if it is strained. For that, you need no polariscope but then again you don't know which side of the expansion viscosity curve you were on the wrong side of either. The more tools you use, the better off you are. I would say that since I got rid of my "Help", I have never had a complaint about a rod or a frit not fitting SP87. or other comparable soda lime glasses.

What I have gotten out of this thread, and I greatly appreciate it, is the need to pay a lot more attention to the annealing point as determined by the spreadsheet as well as physically measuring it . It's also nice to see John Croucher surface after some time in the shadows.

Lani McGregor
04-04-2005, 01:26 PM
It’s great to see John Croucher here. I was hoping he’d show up. And now that he’s here:

John, I understand the problems color bar makers have in being unable to control the melt and therefore the predictability/quality of each studio’s clear furnace glass, but it’s not like there was ever a “standard” – in-house or otherwise – in the kiln-glass world. When Bullseye developed its first line of Tested Compatible glasses, there was no standard either. We had to develop one. We called it “Tested Compatible” - not “90 COE” – and published the test so that anyone could do it. We created and stockpiled a clear standard T-glass for testing. I’d also like to add that the “fused glass manufacturers” (plural) you refer to didn’t exist at that time. We were alone – for a good decade at the start. It wasn’t until one other manufacturer came into the market and wanted to match Bullseye without saying “Compatible to Bullseye”, that the term “Tested Compatible to 90.0 COE” came into the market.

I’m not sure I understand why you say there was no “standard” in the blowing market when you entered, but then say that SP87 was the standard and that you matched that with your own batch. So why not have just called it Tested to Match SP87 rather than having to deal with all this confusion about COEs, which you agree don’t guarantee compatibility?

I know that we all make decisions based on marketing and the interests of being user-friendly, but if those decisions screw with the user’s understanding of the product and process, I’m not sure whether we’re helping ourselves.

(On the other hand, I am regularly reminded by wiser minds in the marketing dept at BE that the Republicans won our last election by having simplistic one-liners and that the Democrats - who thought giving people lots of detail would bring them to intelligent conclusions - LOST)

Finally, I do very sincerely appreciate your willingness to speak publicly on these issues. It is refreshing to find a manufacturer who will come out from behind a website or their marketing literature. And it is undeniable that what Gaffer brought to the studio glass scene was color bar that is controlled to much higher tolerances than the previously existing products. We’ve done some limited testing on rods and “96” sheet glass in our factory and our (again, limited) results show the Gaffer to be MUCH tighter within its own range (not, necessarily in matching a "96" sheet) than any of the other color bar lines we’ve tested.

So. Speaking of compatibility ranges: What is the number of degrees of angle of retardation high and low that Gaffer accepts, i.e., the actual readings on your polarimeter?

Bullseye, for instance, accepts the range between 4 degrees high and 2 degrees low.

Again, thanks for the appearance. (And I apologize for the “full court press” that Jim and I put on you down in Perth 2 years ago – the Pinot made us do it)

Durk Valkema
04-04-2005, 02:56 PM
Sideways ?

Pete VanderLaan
04-04-2005, 03:24 PM
when you say "tested compatible" it doesn't give the user any information about it's relationship to other products out there. "96" does say something about the relationship to other products and most glass people are interested in that relationship. While it is true that some products in the 96 L.E.C. range don't fit other products in the same range, the vast number of them do. That in itself is pretty useful to know. The inconsistencies come when fitting transparent glasses to opaques since they really have radically different structures. Both systems have seemed to co-exist for some time with some incompatibility, but not really that much when you look at the great variety of products offered up to the consumer.

I think John refers to Spruce Pine as the standard in that it was first in the commercial batch community and had a big market share by the time upstart companies like gaffer came along. While it would have been better if SP had not had such a high expansion in my thoughts, it isn't going to change anymore than bullseye is going to suddenly move it's expansion and viscosity either. It is what it is. The choice for a color manufacturer is to adapt to as wide a market as possible or to suffer the consequences of isolation. I forget which of the upstart batch companies decided to make a 93 expansion a few years back making the argument that it wanted to separate itself from the crowd. The stuff fit nothing well at all and was quite short lived.

Language is language based on common usage. Look at the term Dichroic Glass. It isn't dichroic glass at all based on the true definition. Try to get people to stop calling CBS "Dichroic".

When you take the group that won't even melt a batch glass at all and insist on fenton cullets you have yet another glass that is away from the mainstream. It fits little comercial color well at all. People buy lots of it.

Durk Valkema
04-04-2005, 04:42 PM
In the Netherlands in the 60th there was a scene of artists using flat glass from England Germany or France, fusing colours together, adding potash between sheets for volcano effects and at the end holding it all together with the newly developed acrylic and epoxy based glues. Things cracked and empirical experience was developed, hot forming was done in bell type kilns with big open gas flames, very uncontrolled annealing but in the end it was all glued together. Until after 20 years the glue falls apart.
Rods in the blown glass scene where used by factory's well before we where born and with enough knowledge to do the ring test and adjust or even the tests measured on the polarimeter according to the Philips method.
I know Orrefors used to make Kugler hold a melt, get a sample to test on the polarimeter and if it was close enough buy the whole melt.
We at the academy in the 70th, where stuck with cullet from the automated gobbletery at Leerdam, new which colours fit. The cullet was our constant and we knew about the ring and cane tests. Now non of the students have a clue.
Some studio people in the 70th batched themselves but all with links to helpful engineers in the glass industry.
Otherwise it was Harvey's Glassblowing with Erwin's recipes and Frank Kulasiewicz book apart from Sholes and Weyl.
My father started to hand out photocopies of the fascinating "receptbuch fur die praktische Glasschmelzer" by Schmidt to all the interested visitors, I used the book in the early 70th to melt colours at the academy in the colour pot furnace we build knowing vaguely about expansion and ways to make things fit together. Got a hold of S. Simmingskold Ravaror for glassmaltning (Published in 1963) in 1973 while I was at Orrefors. With an add for Polarizing microscopes but no mention of expansions.
Later on in the 70th we got a copy of internal educational material from Philips with very detailed and up to date information on the chemical and physical properties of glass.
Still we used the cullet available to the academy for free.
Pelletised batch came into the picture much later. In the early 80th I did extensive tests for Rhone-Poulenc with their "CRISVER route" material developed by Mr. Richard. An alkaline silicate was made to react with metallic nitrates in water or an organic solvent. The result is a precipitate of organic oxides and by product alkaline nitrate, which is filtered off. During synthesis, these oxides take up the same arrangement, as they will have in the vitreous state. Consequently, such melts vitrify faster and at lower temperatures than traditional compositions. Or so it seemed. One way to try find new markets for their water glass.
Philips started to develop a plant for palletizing there base of hundreds of special glasses that they would melt only a few times a year in there glass factory " Philips Lighting" build in 1980 in Winschoten.
It was not until 10 years later that they started to make there batching facility available to outsiders and market a few basic batches available like a 24% PbO glass with in the tech. info viscosity info and average expansion coefficients:
25-300: 9.35
25-400: 9,65
And an annealing curve.
For the "studio glass" scene they developed a lead-free batch Nr 2500
They knew we used colour rods in our pieces, but the only source they knew about was the Murano cane so the average expansion coefficients at 10,10 (25-300) and 10,55 (25-400)
You can imagine that suddenly a whole different range of colours exploded.
The 2400 worked much better but who wants 2% lead out the chimney every melt.
It took a lot of time to convince them to steer the lead free more towards the German rods.
In the mean time GLASMA was started and again after initially producing exclusively for the factory's they started marketing a lead free pelletised batch.
We knew about Spruce-Pine but that was expensive and far away. Lots of sources for cullet in those days.
Still everybody experimented and knew what to expect most of the time. If it survives the diamant saw its OK.
Very low tech.

Pete VanderLaan
04-04-2005, 04:48 PM
I'm still trying to figure out "sideways".

It's good to know that glassworkers can be lazy on both sides of the Atlantic.

Lani McGregor
04-04-2005, 04:57 PM
Originally posted by Pete VanderLaan
I'm still trying to figure out "sideways".

It's good to know that glassworkers can be lazy on both sides of the Atlantic.

Sideways... as in the movie.... as in Pinot-obsessed freaks that rant on about stuff like...


"Um, it's a hard grape to grow, as you know. Right? It's uh, it's thin-skinned, temperamental, ripens early. It's, you know, it's not a survivor like Cabernet, which can just grow anywhere and uh, thrive even when it's neglected. No, Pinot needs constant care and attention. You know? And in fact it can only grow in these really specific, little, tucked away corners of the world. And, and only the most patient and nurturing of growers can do it, really. Only somebody who really takes the time to understand Pinot's potential can then coax it into its fullest expression. Then, I mean, oh its flavors, they're just the most haunting and brilliant and thrilling and subtle and... ancient on the planet. "

Ya know... like people get on this board about LECs.... over the edge.....

Pete VanderLaan
04-04-2005, 05:07 PM
Originally posted by Lani McGregor


Ya know... like people get on this board about LECs.... over the edge.....
***************************
Ooooh... testy. Or maybe like some people get over the competition in the fused industry. It's all family, just some of it belongs in re-hab.

I have yet to see Sideways so it didn't click. I was way too busy with the Incredibles and the Jack Jack Attack. When I pointed out to my kids that they were a knock off of the fantastic four, they were very disappointed.

Durk Valkema
04-04-2005, 05:14 PM
Lazy? it took me two hours hard work to write my last post. I admit with a wonderful glass of Riesling, Grand Cru Steinert 2002 under my nose.

Pete VanderLaan
04-04-2005, 05:57 PM
Originally posted by Durk Valkema
I Now non of the students have a clue.



I was referring to this.

John Croucher
04-04-2005, 08:18 PM
Lani, it wasn't as if we thought SP87 was a "standard", it was just a very large elephant in the room that was difficult to ignore. East Bay Regular batch played some part in our decisions as well.

Tom, I'd be curious to learn how Nick Labino came up with the expansion/viscosity characteristics of SP87 in the first place.
What was he comparing it to? I presume that he tested it against a selection of Kugler. That must have given him some headaches.

In some ways it was fortunate for us that SP87 had/has such market dominance in the States. Things are much more messy in Europe.

With the polarimeter we look for +/- 3 degrees. Trident seals mostly survive 10 degrees low and 15 degrees high which just goes to show how much glass blowers can get away with.

By the way, Gaffer offers a free trident seal testing facility for glass blowers who want to know where their own batch stands relative to our standard.

Jon Myers
04-04-2005, 08:41 PM
Originally posted by Pete VanderLaan
**********************
One of the main reasons people really liked my black as an example was firstly the density of the color but also the fact that it does not bleed at all and stays absolutely where you put it. . It measures a 96.0 but has a close viscosity match to SP87 and still contains a substantial amount of lead.. It presents no strain in a ring test at all. I find bringing all of the gut features of a glass body to be very contradictory especially when one is trying to match up radically different formulations. I am thinking out loud here and will probably get an earful from someone.

do you think that it is tight because it is so reducing. John Curtis showed me a decorating trick that has a normaly soft lead oxidising color on top of a reducing clear or carbon amber or some sort of heavy reducing glass (Cu ruby). normally you can't make tight designs with, for instance, R144, but on a reducing glass it stays put. I think that is why r95 is so sloppy (heavy oxidising)and your black is tight.

Phill Cusens
04-05-2005, 12:20 AM
Some 18 months ago I asked about the trident seal test, I got replies that I could not agree with. It is probably the most simple test for testing "compatability" of one glass against a standard, it is far easier than the ring test and infinately more accurate than the thread test.
It seems to me one can get one's recipe to within a point or three of where you want to be by using English and Turner's! Well within the ball park to use the Haggy Trident Seal test. Obviously one would have to choose a standard.
My guess is that there are't many glass blowers out there, especially the week end warriers, that could make an accurate ring to test.
All that is necessary is that you look at the Gaffer web site and send a piece of cane and Gaffer will test it free of charge now waht more could you ask.
This has been a very educational thread and I congratulate all who have given thoughtfull, intelegent input.

Tom Littleton
04-05-2005, 10:15 AM
I don't know what all went into the decision making proscess that resulted in the Labino formula. We had another guy working for us at the time that did the talking with Nick.

In the early 80's, Nick gave a lecture at the Gas conference (I think the one in Toledo) pointing out how bad the glass was that the studio blowers were using. (I believe he focused on the problem of durability in the lecture.) This glass was primarily the cullet coming from the handglass factories. In addition, by the time he started working on the formula Nick had spent more than 20 years experimenting with various glasses with with the perspective of using them in the studio and for blowing. I'm sure he had lots of Kugler lying around as well. Before coming to Studio Glass, Nick was invoved in the fiberglass industry.

In addition, Nick gave us the formula in the form of a chemical analysis and the original formula did not include the lithium. We had to translate the chemical furmula into a list of materials. This would have changed some of the charateristics slightly and the later addition of the lithium would have also effected things. Then I think the actual coe that was arrived at for the 87 was more happenstance than design and more our work than his as we did some adjusting of the coe until we arrived at the 87. We were trying for something that fell within the range of variation (that is would fit) of the most popular Kugler colors (the transparents and the 61 white and black). We aso wanted it to melt as easily as possible without sacrificing too much fit.

We made another adjustment to come up with the 83 but the 83 never really took off in the marketplace.

Pete VanderLaan
04-05-2005, 10:41 AM
Originally posted by Tom Littleton


We made another adjustment to come up with the 83 but the 83 never really took off in the marketplace.

*********************
which is worthy of note since the kugler opaques were (I believe) the target glasses the 83 was shooting at. The kugler opaques do not really fit the SP87 or any other commercial clear batch out there on either L.E.C. or viscosity or annealing curve or phase of the moon.

Gaffer's opaques ( and mine) were engineered to fit the current clear batches, but not the cullets.

Lani McGregor
04-05-2005, 10:55 AM
Originally posted by Pete VanderLaan
Gaffer's opaques ( and mine) were engineered to fit the current clear batches, but not the cullets.

Pete, which "cullets" are you referring to? By "current clear batches", I assume you mean SP87 and Gaffer? Remember, I'm from the Kingdom of Kiln and don't always understand your language ...

Pete VanderLaan
04-05-2005, 11:14 AM
In 2001 we had

Spruce Pine 87
Spruce Pine 83
Spruce Pine 92
Gaffer
East Bay Regular
East bay opaque
East bay Something Else
Gaffer from Phillips ( East Bay)
OLYMPIC COLOR- Phillips something
ELECTROGLASS Phillips something Clone
CR LOO GLASMA 70 or 71
Corning Batch Company
Pennsylvania Batch Company
Laguna Clay SP87 Clone and others
Phillips many formulas
GLASMA other formulas

In cullets we have:
Fenton C-4
Fenton C-6
Other Fentons
Seattle Batch CBG
Spectrum 96
CR LOO Something
Bullseye Clear
These are all over the map
and I'm sure I'm leaving some out. At Least DryKiln Crystal A is gone and so is Keystone cullet.

It gets far worse when you add in the european and australasian stuff.


Some of these have come and gone, Some new ones try to enter the market. Some, like Vermont Batch, never actually made a pound of batch.Most but not all are 96 glasses, which is why 96 is the elephant in the room. Almost all are terrible casting glasses which is tied to their formula structures.You are far luckier than you realize.

Tom Littleton
04-05-2005, 03:08 PM
Isn't that Gabbert C4 and Gabbert C6?
Not to be picky or anything.

Pete VanderLaan
04-05-2005, 04:55 PM
go ahead, be picky. I think the point is made anyway. If you actually can't remember the names, then there must be lots of them. If it is Gabbert, which I have no doubt that it is, I think there are fenton cullets as well. The more the merrier. I would think that Lani gets it by now.

Pete VanderLaan
02-28-2006, 09:41 PM
bump