View Full Version : Brossphate v. Cristalica

Dan Vanantwerp
04-30-2018, 11:40 PM
I melted my first batch of Dave's phosphate opal this weekend. It was the straight formula:


The compatibility tests did not make it out of the annealer...except for a couple and they blew apart right at the saw. First pic has some all-brossphate pieces to show the color at the top. At the bottom, the broken pieces are inside or outside color-clear...no difference. Last 2 pics show the color intensity achieved for a couple all brossphate pieces.

I've got my work cut out but I'm hoping for a little direction. My only clue is the E&T measurement which for Dave's 2.5% is only 92.6 while Pete's silver opal is 94.1. The silver opal has fit perfectly for me to Cristalica with ring tests for final proof. I have no idea what the Cristalica E&T would be so I have to make a guess that it's closer to Pete's than the Brossphate.

I'd like to intensify the phosphate similar to Jordan's results. Coincidentally, I can raise the E&T to 95.1 by increasing the phosphate 3.6%, but is this really a good way to modify the expansion? Pete usually points to soda ash and sand for moving the expansion. Should I use soda/sand to find a compatible 2.5% glass or just modify the phosphate and see if I can kill 2 birds with 1 stone?

Thanks for any input and to Dave for sharing this formula. My results need work but that was really fun to work with!

Pete VanderLaan
05-01-2018, 07:41 AM
cristalica is currently about a 97.

Dan Vanantwerp
05-01-2018, 12:57 PM
OK...that gives me a direction. Thanks.

Jordan Kube
05-01-2018, 03:25 PM
Using Dave's calculator I would shoot for 91 LEC for something compatible with Cristalica. My notes indicate the more phosphate you add the lower your target number will be. I melted a 5% that showed 1 point high in a trident seal but no stress showed in the product under the polarimeter. The calculator shows a theoretical 87.75 LEC. Melting a phosphate opal will yield different results than a straight soda lime calcedonia. You can really only rely on your previous phosphate tests as a guide.

Dan Vanantwerp
05-01-2018, 04:29 PM
Wow...thanks Jordan! I had a hunch that making LEC adjustments with the phosphate was a bad idea. I am awaiting a package of a la carte ingredients from Jim at East Bay including his sand. I'll be able to tune this in a bit on my next batch.

I'd be interested to know if you got the fit worked out for the 5% with 1/2 borax and if it needs 2300 to melt.

Jordan Kube
05-01-2018, 05:11 PM
I considered the 5% recipe compatible due to the product showing no stress. I melted at 2300 and I would recommend higher if possible. Go ahead and make LEC adjustments, just don't rely on your non phosphate batches as a guide.

Dan Vanantwerp
05-01-2018, 05:25 PM
Hi Jordan, I'm paraphrasing your last entry on the 5% Brossphate post:

"Added half of Dave's borax after reading boron was helpful, added .75% cryolite for same, ... Just need to adjust expansion now."

Was the "adjust for expansion" not needed?

I'm really only interested in doing this at lower temps...2200 max. It melted fine with the full amount of borax so I'll work with that. It did seem to have a sweet spot in the pot so I'll have to work on stirring more.

Jordan Kube
05-01-2018, 07:24 PM
Yeah, I would definitely keep full borax. Still the crap out of it while it's melting. The first melt was 4 points high. I adjusted it down.

Dan Vanantwerp
05-01-2018, 09:49 PM
Thanks again Jordan. I only get a couple shots at melting on the weekends. You have probably saved me weeks of aimless testing. I'll report back on my progress.

I visited the Glassbaby website and found the company's concept and structure to be super interesting. I'd like to know more about its origins how you got involved.

Pete VanderLaan
05-02-2018, 07:18 AM
my runs at dave's phosphate worked with my clear just fine. That makes me wonder about your supplies, like for borax. 5 or 10 mole? Whiting as opposed to Lime Hydrate? Feldspar?

Dan Vanantwerp
05-02-2018, 11:34 AM
Good points. I used 20 mule borax from the store which is 10M. I performed a molar equivalent calculation to determine the correct amount to add. Derived this little chart for my own quick calculations.

Borax equivalents
5M lb 10M lb
1 1.31
5.2 6.80
9 11.77

Jim doesn't carry lime hydrate and instead used a high purity whitening. I took a cue from your conversion of the unoxidized formula going from lime hydrate to whitening and again performed a molar conversion on the calcium content.

Calcium equivalents
Whitening lb Lime lb
1.35 1
7.42 5.5

The formula doesn't have feldspar...just alumina hydrate.

One of these changes may have caused issues. I worry about the use of whitening but as you were exchanging it in the unoxidized I really wasn't concerned about it. Jordan's point about all rules being off on this type of glass has me questioning everything.

Dave Bross
05-02-2018, 12:47 PM
Once you get the expansion dialed in a few extra strikes will make it quite a bit more opaque.

Pete VanderLaan
05-02-2018, 12:55 PM
It's called "Whiting" and that's yet another name for Calcium Carbonate, also called Marble Dust, Lime, and a few others but it's all CaCO3. Hydrate is CaOH. Big differences on that Borax as well. Most formulas call for 5 mole, not ten. There is also anhydrous borax.

In some spreadsheets, it may not let you try both so the thing to do is to zero everything in the spreadsheet and then just add the single item, like feldspar. Then look at how your spreadsheet( that you likely didn't write) assigns the components for feldspar. Some will now be silica, some alumina but then it gets interesting where it puts sodium and potassium and in some cases (spodumene) lithium. The same sort of thing will happen with Borax, or alumina, so pay attention. The differences between Hydrated alumina and calcined are large.
After that, you may develop interest in how much moisture you are carrying around in a bag on chemicals that is additive and not chemically bound. If you had 1% moisture in a 100 lb bag, it's got 1 pound of water in it. Continue pondering that math when you look at expansion factors. Fritz used a simple trick to determine moisture. He put 100 grams of the questionable material in an annealer and turned it up to 250F for four hours. Then he measured the weight a second time. If it now weighed 97 grams, it was 3% water.

Doing this successfully requires a lot of careful deliberation and some occasional navel gazing.

Jordan Kube
05-02-2018, 09:51 PM
Yes, those were my results. Yours may differ for a variety of reasons. All rules aren't off, the formula is only relative to itself and other similar batches.

Dan Vanantwerp
05-03-2018, 10:21 AM
"the formula is only relative to itself and other similar batches"

That's a much better way to put it. However, when you're trying to match a clear as I am it seems like the rules have to be bent a bit. Your observation that a LEC of 91 is needed for a 2.5% phosphate and 87 is needed for a 5% is showing a trend where the spreadsheet says one thing and the glass does another. My results seem consistent with yours in that the original formula at 94.1 is not compatible with Cristalica. We'll see if a straight-forward drop of LEC to 91 makes all the difference.

Both Pete and Dave make their own clear and colors. They found their clears to be compatible with the straight Brossphate formula. Could be that their clear formulas are a better match to Brossphate. Pete's is much different from Cristalica as he has described. There is more than COE to compatibility as your results make clear. That their clears are also compatible with 96 colors would seem to make them a better choice. Who knows how the Brossphate (@91 LEC) is going to react to a 96 COE color when the LEC is pushed down just to fit the Cristalica.

Pete VanderLaan
05-03-2018, 10:47 AM
quit using the term coe.

Jordan Kube
05-03-2018, 03:18 PM
Don't over think it. Just work with what you have. Make a change, observe the result, make another change, rinse and repeat. The only thing that is really a constant is the clear you are using. Make it compatible with your clear and you shouldn't have a problem with *most* colors out there. If you do, chances are that other color may have been a little on the fringes of compatibility as well.

Dan Vanantwerp
05-03-2018, 04:06 PM
Thanks Jordan. I'm actually hoping to start using Pete's clear but it is worth the effort, I think, to make things work in Cristalica also.

On another note...I recall you were not happy with the castable you originally used for your crucible chamber with the element channels. Did you find a good material for that purpose?

Jordan Kube
05-03-2018, 05:18 PM
It's fine, I just needed to cast the bricks a little thicker and put a release between them. I'm rebuilding on Saturday and everything is getting a skim coat of pumpable frax on it.

Pete VanderLaan
05-03-2018, 05:23 PM
Solve one problem at a time. I can't stress that enough.

Dan Vanantwerp
05-03-2018, 06:49 PM
Might sound stupid but I wish I could be there to help. I'd enjoy seeing someone else's approach to element furnace building. I just do my best without a whole lot of knowledge or experience. I'm a good weldor/fabricator but that's just a small part of the success of a build.

Don't worry, I'm not trying to invite myself...I work this weekend :)

Pete, thanks for the advice on keeping things linear. I'm completely isolated from other glassblowers here in Bozeman and sometimes just go off on tangents to discuss glass with you folks. It's tough to just be your own sounding board all the time.

Dave Bross
05-07-2018, 09:47 AM
To go a touch deeper on Pete's "quit using the term coe"

What really matters most is that the glasses match expansion at the point where they set up...usually referred to as softening or strain point. This gets tricky with time and temp but fortunately you can overcome much of the trickery by moving the expansion of one of the glasses.

Quite often two matching glasses will have very different calculated expansions.

Think of the calculated expansion as a number you use to see where you're going as you experiment to make two glasses match.

More detail:


Dan Vanantwerp
05-07-2018, 10:31 AM
Thanks Dave. I didn't really want to go into it because it's obviously a pet peeve of Pete's...wow say that 5 times fast!

For me, "96 COE" just describes commercial glasses because that's all we know about them going into it. Should fit...might not.

Pete VanderLaan
05-07-2018, 01:40 PM
Linear expansion Coefficient L.E.C describes the linear expansion of a glass, nominally in a 4.000 length approx 4mm in diameter heated from 19C to 300C.
That's where your number comes from.

Coefficient of expansion doesn't even say what kind of expansion. C.O.E. I believe was an expression Theresa at C&R Loo used way the hell back when, and she was trying to get some useful information out there about what might fit what when information was in short supply. It does not mean anything however, thus my objection. Lani MacGregor queried about this and you can find the thread on that in Antiques and Classics.

Since varying thermal guides have been used in various tests, the temperature range has varied. Some systems tested from 19C to 300C, some tested from 200C to 400C. There's a lot of odd stuff but it becomes apples and oranges. So you get to where SP87 is actually a 96... E &T never tested colorants at all. Winkleman and Schott did do an enamel study back around 1925 for that industry on many metallic oxides but the temp ranges were not comparable. A major mistake was made in 1975 or so when Paul Manners put together an article for Glass Magazine called "Custom Made to Fit" which was a very helpful application of Algebra to the issue. There was however a fatal flaw and Paul co-mingled the different studies into one chart. Then Henry Halem canonized that mistake by including it in Glassnotes 3. Fortunately Henry removed that at my urging before Glassnotes 4 was taken to print. Appen does have a far more complete set of factors but it does assume you will calculate your glass using mole chemistry to really be accurate.


Dan Vanantwerp
05-15-2018, 10:29 AM
With the guidance from Jordan that his 5% is a theoretical 87.8 LEC to match Cristalica, I made a 3.2% with a 90.2 LEC. Wanted to try a bit more phosphate for the white I want to achieve.

Good news: I love this glass! The color was amazing and came on easily after just a couple strikes. Melted well even with more silica...lots of stirring and kept my borax level the same. I'm doing an overnight at 2180 after melting it all down at 2112. Both the Brossphate and my chalcedony really like this high temp period to get everything melted in.

Bad News: Made it out of the annealer, but...no rings for a test. I sawed another cylinder of known compatible glasses and that was fine. I'm going to try and get closer to Jordan's 5% LEC number next time.

Wash...rinse...repeat :)

Dan Vanantwerp
05-22-2018, 09:36 AM
Pushed the LEC to 88.7 this weekend. The phosphate strike remains the same with a solid white coming up after just 1 or 2 reheats. Very nice color. I also feel like I'm getting better at melting this glass with multiple stirs and a long higher heat to 2180 (8-10 hrs).

The compatibility tests with Cristalica were consistent for 2 cyclinders each; Brossphate inside clear and clear inside Brossphate. The encased Brossphate again made it out of the annealer but still cracks on the saw. Brossphate over clear does not even make it to the saw. Cracks shortly after removal from the annealer.

I'm going to drop the LEC to Jordan's 87.8 LEC number for a 5% phosphate glass...even though mine is at 3.2%. I believe the expansion is being driven by the saturation of tiny PO4 bubbles. A 5% might get to saturation faster, but a 3.2% gets there eventually. Either way, the final result on expansion is the same (I hope).

This brings up some interesting issues with using this glass. See the Gaffer Glass tech notes:

This glass has the potential to change it's LEC based on the work time and reheats. I suppose it is possible to land on an LEC somewhere between a dense and veiled opal (good luck). Working with it alone is a possibility but at some point it begs to be married with your favorite color patterns.

I started wondering if this is happening to some degree with all opal glasses we use. This Brossphate is making me think about glass in different ways. It's been a great experience and I look forward to getting a fit. Not sure it will work for encasing/overlays and I wonder if Jordan or Dave ever got it working in this capacity...

Pete VanderLaan
05-22-2018, 09:51 AM
It is not the same as with other opals. Your phosphate is a phase separation glass: One phosphate glass embedded in a silica glass. On reheat the phases separate leaving a bazillion fine bubbles to reflect light.

A fluorine opal is very different, using fluorine to combine with either alumina or calcium to make crystals that are in the glass. If you didn't have the alumina or the calcium, it wouldn't make the crystals. Those crystals grow, collapse and grow again as the glass winds down its intensity.

If your samples are either breaking up on the saw, or just by themselves, You are likely at least two full points out on the mismatch, perhaps more.

Dan Vanantwerp
05-22-2018, 01:37 PM
The Brossphate on the outside is even less compatible than when encased with clear. Does this tell you anything about the direction I'm off?

Thinking of dropping it down to 87 or even 86.5. The current batch was less runny than previous versions but it's still very workable. Does seem to be shortening the work time, however.

Pete VanderLaan
05-22-2018, 02:37 PM
It seems to me that if the glass on the inside has a lower expansion, it's more tolerant. You should probably try something radical like changing the soda by around a half percent and see what it does.

Dan Vanantwerp
05-22-2018, 04:02 PM
Thanks Pete. I was hoping that might provide a clue. I'll give it a shot.

Dan Vanantwerp
05-24-2018, 10:28 AM
Last weekend, I made a cylinder with chalcedony on the outside and Brossphate on the inside similar to the Cristalica compatibility tests I ran. I let it sit a few days before running the ring test. Almost did not bother after my previous results. Survived the saw, made rings and had no movement in the vertical crack test. Looks right on.

The Cristalica versions were run a couple hours after being pulled out of the annealer. They were cool and I thought "done". Going to repeat the tests with a longer cool time. I really don't think the Brossphate outside results will change. Both my tests cracked an hour or so out of the annealer. I have a rather long annealer cycle as I was using it to try and coax more colors from the chalcedony glass. I think it's allowing for a good strong annealing. We'll see what happens If I leave it alone for a longer time.

I am posting mainly to let others know about the timing difference. I'm new to ring tests and was really surprised about the possibility that annealed was not "ring-test ready" annealed. Learning...

Pete VanderLaan
05-24-2018, 01:29 PM
If a piece can't survive sitting by itself after being out of the lehr for two hours, it really is not close to being compatible unless you're talking some massively thick thing. A regular glass, in the shape of a cylinder, about 1/4-1/3 inch thick, about three inches in diameter will do admirably. Do make sure your saw has adequate coolant and the blade has diamonds on it.
If the piece cracks, almost with a shudder, the moment the blade touches it and breaks the surface tension, you were way far off. You really should be able to saw the ring ( about an inch inch wide). My experience tells me if the ring survives that, it's compatible. I've seen some exceptions marrying lead to soda lime where it can take an hour or so to crack after that but in general, similar glasses are good matches at that point within the constraints of 1.5 ten thousandths. The vertical score that you tap clean is going to tell you how to fine tune the glasses and we outlined that as a graphic in glass notes, so look at the graphic.

John prefers the Hagy seal and I get that. It's worth noting that if the Hagy seal is more than about 2.0 off, it breaks before you can ever test it. The ring doesn't have quite the same issues. If the glasses are similar, you can do a simple pull test with canes and they will tell you a lot as well. They're in the lassnotes IV as well. If you don't own the book, you really need to get it. Henry put together a great compendium.

At any rate, you don't need to cool it that long. I just put mine under cold water before sawing if I think it's a bit warm. If that breaks it you need to change your glass.

Do keep in mind what annealing is doing and the range in which it happens. From deformation point down to Strain point, you can relax the inherent tension in your glass. Soaking the piece is the most critical aspect of the process. Putting it away hot enough to not need to overcompensate is important as Frank Wooley noted long ago. The thickness and the rate of reduction of temperature are indeed important down to Strain Point but remember that once you pass Strain Point, no further annealing can occur. At that point you're just trying to prevent thermal shock.

Pete VanderLaan
05-24-2018, 01:35 PM
I am posting mainly to let others know about the timing difference. I'm new to ring tests and was really surprised about the possibility that annealed was not "ring-test ready" annealed. Learning...
I don't know why you say that. If the piece is annealed and room temperature, it's ready to attempt sawing it.

Dan Vanantwerp
05-24-2018, 03:44 PM
Thanks for giving me some feedback Pete. I thought my process for testing the rings should be ok but last night's result really surprised me.

I'll keep your points in mind when I test again this weekend. I do have Glassnotes and will look over the relevant sections.

Thread tests looked fine which also puzzled me, but I noted that it's not the most definitive test out there.

Kenny Pieper
05-24-2018, 04:36 PM
I hear people all the time express that they leave their pieces for days to "rest" before cold working them. This is simply not necessary. Once the piece is room temperature it either has stress or not. In fact once it gets through the strain point their can only be temporary stress introduced to the work. So cooling too fast after the stress point will either break the piece or not but you will not be giving it a stress that is lasting. The same is true after the piece is room temp. You can cause stress in the glass by heating it too much while cold working or other aggressive actions, which can break the piece, but you will not be giving it permanent stress.

Pete VanderLaan
05-24-2018, 05:34 PM
listen to Kenny

Dan Vanantwerp
05-29-2018, 10:00 AM
I ran the Brossphate 3.2% @ 88.6 LEC again just to be sure all my compatibility samples were run in the same way. I am testing it versus Cristalica and Pete's silver opal batch (chalcedony). Pete puts Cristalica at 97 LEC and my estimate for the chalcedony is 94.1.

I was afraid that I was complicating issues by testing against 2 glass formulas but now I am glad I did. It allows you to make the expansion variations and find fit where it occurs rather than starting all over again with another test. You are also using the exact same glass and can erase any questions about batch formulation.

The chalcedony is matched to this glass...inside and outside. Brossphate over Cristalica still fails before it gets to the saw while Cristalica over Brossphate fails after a few inches of radial cutting on the cylinder. I could get a solid ring from the top of an open cylinder. It contracted a bit after checking the ring. Both results suggest that the Brossphate is lower than Cristalica. I'll bump the Brossphate up to 91 (as Jordan originally suggested) and retest. I ran a 90.2 a few weeks ago and did not find fit so kept going down. We'll see what happens.

My worry is that Cristalica-Brossphate-Chalcedony will not fit all together. This combination is really fantastic and I looked forward to contrasting the opal swirls against a variety of Brossphate color backgrounds. I can still do that but without a clear encasing which really finishes off the chalcedony.

My other option is to change the clear. This may be the final nudge I need to do so.

Eben Horton
05-29-2018, 11:03 AM
Donít change your clear. Thatís asking for nightmares down ththe road.

Dave Bross
05-29-2018, 12:49 PM
Do thread tests for a quick idea of where you're at, then more advanced testing when the threads are looking good.


Dan Vanantwerp
05-29-2018, 12:59 PM
Thanks for the warning, Eben. Point well taken. However, I'm considering myself as starting down the road at this point (15 years in). Small batch color is the way for me to go. Besides, I've already had to change my clear 3 times based on the availability of cullet. I can make a clear with Pete's unoxidized (base for the chalcedony) easy enough. Also hoping to try the newest version.

Dan Vanantwerp
05-29-2018, 01:08 PM
Hi Dave. Thread tests didn't tell me much. Everything was straight as could be. I just sort of slap gathered a dab of cristalica next to a dab of Brossphate. I even brought out the phase separation to make sure I was looking at the final glass. Worked great without having to get out a torch. You could see the even pull of both colors coming into the thread.

Eben Horton
05-29-2018, 02:10 PM
If you pull a pull test and then give it multiple flashes, you are re annealing it and might be fooling your results. Iíd get it it hot, pull it, and then let it cool. Thatís it.

Dan Vanantwerp
05-29-2018, 02:48 PM
I have to say that I tried a few different ways. I gathered a little clear then a little brossphate side by side. One time I pulled the thread right out of the pot, but also tried it after cooling and heating a couple times. The threads were never reheated just the side by side gobs on a punty. No matter what they just stayed straight as a string.

Ring test is much more telling.

Kenny Pieper
05-29-2018, 03:42 PM
I have to say that I tried a few different ways. I gathered a little clear then a little brossphate side by side. One time I pulled the thread right out of the pot, but also tried it after cooling and heating a couple times. The threads were never reheated just the side by side gobs on a punty. No matter what they just stayed straight as a string.

Ring test is much more telling.

You are right that the ring test is much more accurate.
When it comes to the thread test I think you need to start at the same temperature and amounts. In you case I would gather some of the opal on a punty, strike it, marver it out into a finger shape. Then gather the same amount on another punty shape it the same, stick the two together and heat them a couple of times to make sure they are the same temp before pulling them. It sounds like you base glass and the opal are not necessarily similar formulas so this may not tell you all that much.
If the two glasses are simular this will give you a good start
I have a very dense black that I make that is quite soft and if I make a thread test that is straight I know that it is incompatible.

Pete VanderLaan
05-29-2018, 04:17 PM
Chuck used to say "Sometimes you're so far out, you're in".

The ring test and the Hagy seal just don't calm your lying eyes. They speak truth.
Quit trying to calm yourself with "the on the outside it's better than on the inside. ".

It's better when you just saw it and it cuts clean.

Dan Vanantwerp
05-29-2018, 04:42 PM
Thanks Kenny. I thought of making a couple rods and then performing the thread test but figured it would work fine from side by side gathers. The heat was definitely the same as they were on the same punty. Amounts were variable, though. I would try and refine it for a more accurate deflection measurement but there was just no bend.

Hard to say how different the Brossphate is from Cristalica but given their purposes I would say they are likely quite different.

I can cut a ring from cylinder that is layered...Brossphate-Chalcedony-Cristalica. No stress is indicated in the ring test.
Knowing there is stress, but that it is somehow offset in the layering, I do not plan on using this combination. Should a successful ring test bring me calm in this instance?

Pete VanderLaan
05-29-2018, 05:58 PM
Don't forget to evaluate your basic pieces. How do the individual glasses do in the saw with no laminations at all?. Sometimes the annealing is the thing overlooked.

Dan Vanantwerp
05-29-2018, 10:54 PM
With so many failed ring tests I used a self over self layered glass to test my sawing technique. Worked fine and Brossphate by itself sawed great. Annealing is good. I think I may just be happy it is matched to the chalcedony and move on.

Pete VanderLaan
05-30-2018, 09:56 AM
Weyl suggests that chalcedonia is actually easier in a phosphate base. If you don't have weyl ( Coloured Glasses 1951, 1954 ) , get it. It's a very though read, particularly compared to Volf but in actuality, Both authors are quite dismissive of silver bearing glasses except in silver staining. It is a real fugitive and despite rigorous control it's going to give you a good deal of heartache for no discernable reasons.

Dan Vanantwerp
05-30-2018, 10:10 AM
I threw about 50g black tin into ~20 lbs Cristalica cullet and used that to encase the chalcedony. Seemed to bring out some more opacity. Also loved the way silver chloride nuggets flowed over it. Is there a simple addition to help remove the yellow tint?

I'll look for Weyl.

Pete VanderLaan
05-30-2018, 11:49 AM
I have never tried adding black tin to cullet so I don't know. The yellow is the main color silver presents. If Calcedonia gets stirred, it turns gray. It is self defeating to gather calcedonia glasses. stirring is to be avoided. Heat treatment is really key to success. Hot then cold, then warm maybe then cool. Then hot, then cool. It goes on and on. I am currently making full pots of it at 80 lbs and there is no clear in the work at all but I do have three pots of the calcedonia, all tone different from the main pot. Fun but pricey. It looks like views from the Hubble.

Dan Vanantwerp
05-30-2018, 01:02 PM
When I was finalizing the formulations with Jim he asked if I wanted to add a decolorizing agent. I think he mentioned cerium. I wanted color in those batches so I declined, but perhaps it would work well in my reduced clear cullet. It is a pee-ish yellow probably on its way to amber with more tin added.

Pete VanderLaan
05-30-2018, 01:29 PM
Cerium is not a decolorizer. Erbium would be a choice but it leaves a faint pink meant to block green tones as did selenium with cobalt. I don't really understand what you are trying to do, or why. It just seems all over the map.

Dan Vanantwerp
05-30-2018, 01:52 PM

Dan Vanantwerp
05-30-2018, 04:19 PM
Hi Dave, you posted this a while back...

"Throwing in about 20-25 grams of black tin per 10# glass (preferably batch for better mixing) with any glass you're melting = instant reduction glass.

Reduced clear on top of reactive glasses = fun. Reduced clear frit on top of reactive glasses = more fun.

This will radically change or disappear some colors so if you're thinking of doing it with a colored glass check with us first.

As already mentioned, you don't need to do this with colors that require reduction to exist, such as copper ruby, silver glasses. etc."

What colors are "Reactive" to you, if not the silver glasses? I looked at the reactive colors in opaque and transparent from Olympic and they are mostly the Iris colors which are silvers. There are others, but I was curious what you defined as the reactive colors.

Bead makers have the best color tricks, IMHO :)

Pete VanderLaan
05-30-2018, 05:01 PM

That's a first for me. Given that they mention manganese at all makes me really question that statement. Manganese went out years ago and was globally replaced with Cobalt and selenium which in turn was replaced by Erbium. I don't know a single person who does that. I use erbium if I need to. Cerium would certainly be less expensive. I tend to buy clean enough silica to not really have to do it at all. Short Mountain is very clean stuff. Further, if you are combining virtually any color in your work, you would never notice the difference between a decolorized glass and an untreated one.
Gold and silver glasses are reactive with each other as with copper. Silver is the influence in making Gold glasses change from simple rubies to iris etc.

Adding black tin to a clear is kind of setting up a dog fight between glasses poor in oxygen and glasses that are rich in oxygen. I used to watch others in Santa Fe pouring enormous amounts of silver into clear cullet to get the same reactions one would expect in an oxygen poor glass.

Pete VanderLaan
05-31-2018, 07:44 AM
So, I am incorrect but with a large caveat. Volf indicates that Cerium can indeed be used as a decolorizer but only in the complete absence of Antimony, Arsenic or Vanadium. Even then, it is best coupled with Selenium and neodymium with a potential sneeze of manganese. It's on Pages 401-402 of Chemical Approach to Glass. It certainly surprised me and I would be inclined to stick to Erbium if I was doing it at all.

Dan Vanantwerp
05-31-2018, 10:13 AM
I just bought Coloured Glasses from Weyl. Good price on Amazon...$50 in paperback. Volf is at $200 currently.

I looked at the price of erbium when Jordan described his pink color test and it was pretty $$$. Must work well if you would rather use it to remove color.

The mechanism of action for the decolorizers (as described by CMOG) is oxidation of tramp metals. It wouldn't make much sense for me to add oxidation agents into a glass that I just made reducing...like your dog fight analogy. The yellow color is just going to have to be a side product. I'll add less tin next time.

Do you think it is the tin or something else in Cristalica that is turning yellow?

Pete VanderLaan
05-31-2018, 11:21 AM
If I had to decolorize, I'd use Erbium. I think 8 grams per 100 lbs is not that much to spend on.

I have on numerous occasions tried to make a cerium Titanium yellow and never had any success at all. I am not sure what Cristalica uses for a fining agent. I would have used antimony trioxide as my tool of choice but it is popular now to use sodium sulfate AKA saltcake. Now I just tried that at a friends suggestion on a reducing glass and it really discolored it badly to where I won't try that again. I think I put 50 grams of saltcake in 80lbs of a selenium pink glass, replacing 50 grams of sodium carbonate so I did not consider that to be a lot of S03 being replaced. It really darkened it badly. I have the spec sheet on the Cristalica and don't see anything there that would cause a yellow tone as I see it. I would not think having black tin in your reducing clear should be a source either, but if you say it's yellow, it's yellow. Iron can do strange things and it certainly has a bunch of valence states.

Weyl is a tough read. You will do it many many times if you are serious. I found after about ten years it made more sense. The problem I have is particularly with the treatment of silver. Both Volf and Weyl act as if it's a renegade to be avoided and I think the renegade part is true but don't think you're going to settle in with some consistency, you won't. It will go south on you in a heartbeat.

In the Joy of cooking, Julia Childs offers up an interesting recipe for mayonnaise. It is straight forward enough until you get to this cryptic observation " "Don't bother trying to make mayonnaise in an electrical storm".

I have certainly been known to have trouble with some colors when the barometer falls. Less air pressure is less air in the blower. She's into ionization.

I think the price on Volf is stable. Mine is hardbound and he printed 20 of them but I had thought the paperback was less. He may be running out. Those things all have the life of a mayfly. If you can find "Recipes" by Finn Lyngaard, grab it. Igneous glass had a limited number of copies Finn's widow sold him. Finn is dead and gone but the Thuringen recipes are just jewels. It is in the Rakow in the original German. Volf , I've seen as the 1981 original priced at $2,000 or more.

Dan Vanantwerp
05-31-2018, 12:35 PM
8 grams erbium should be very doable. I'll give it a try and see what happens. I really liked that pink Jordan got and with some left over erbium will be tempted to try that also. Pink and purple use to sell much better for me...everything is cyclical.

I'll snap a photo of my punty bucket...looks like the dog peed on it.

I'm ready to place a new order for unoxidized batch via Jim. Any chance you two were able to chat?

Pete VanderLaan
05-31-2018, 01:58 PM
Jim dropped the ball and went off to Murano. I don't know if he has come back yet. We have certainly agreed he can mix it. I'll write him again.

If your clear was decolorized with selenium, it's possible you could get a yellow tone. I remember Spruce Pine inadvertently getting a pink at one point that was attributable to Se. Just not a yellow. The Goddess Selen is an interesting woman. I just can't see using cerium for that. Any Cristalica I have from when I brought the stuff over here from Dobern two- three years back for Spruce Pine ( Jeez time flies) showed no color at all. It was water white.

Dan Vanantwerp
05-31-2018, 02:53 PM
Thanks, Pete. I'm hoping he's back but not sure. I've been waiting to try him as I imagine the backlog of orders is nuts.

I can suggest only one other source of metal contamination in my clear. I made the Cristalica frit that I mixed with black tin by ladling into a galvanized bucket full of water. I doubt much zinc would have come off but surely some did.

Pete VanderLaan
05-31-2018, 03:12 PM
I'm currently fishing about to see if anyone else is experiencing what you are seeing. It's the same as in crucibles. When I get a single call as a complaint, I always start asking around if anyone else is having the same problem. If It's "Yes", it just became my problem. If it's "No", then its another person either mistreating their pot, or just not understanding that they don't last forever.

Cullet, when it's being bad is quite indiscriminate. It goes after everyone and thy finally do compare notes. That's one of the things I love about craftweb. Strength in numbers. I have a few calls in, here and there. i'm at a loss to explain yellow. I can explain other things, but not that. Again, the stuff I have in the tractor shed is water white . I don't think the Zinc explains it at all.

Dan Vanantwerp
05-31-2018, 04:04 PM
Just for some additional info:
That crucible has never seen anything but Cristalica and this was my first time adding black tin. I had about 1/4 glass left of a 80 lb crucible at the end of a day. Added 20lbs fritted Cristalica with 50g black tin. Went from clear to yellow overnight.

Will post a color pick later.

Pete VanderLaan
05-31-2018, 05:16 PM
Staying away from this: Are you melting any cristalica without additives? What do they look like?

I have always added black tin to a raw batch, never a cullet. What I wanted was a clear that wa receptive to having such materials as Silver bromide to it and in deed it was receptive. Silver flowed on the surface, it never balled up as I would expect in an oxidized clear.

Pete VanderLaan
05-31-2018, 05:20 PM
Jim confirmed, he does not use cerium as a decolorizer. ( no one does actually, despite CMOG) .Start over.

Dan Vanantwerp
05-31-2018, 05:44 PM
I didn't mean to sidetrack you with the idea of cerium as a decolorizer. I should be more careful when I mention things in relation to Jim. I don't doubt that I just heard him wrong or didn't remember what he said.

I never add things to my clear Cristalica. I don't even wash it...just goes from the box into the crucible. The main reason I noticed the yellow was because it was such a contrast from my normal clear.

Pete VanderLaan
05-31-2018, 06:22 PM
So, normally the cristalica is clear? So if you add the black tin, it changes colors? I admit surprise but if you turn it to frit, is there a difference between fritting in a galvanized bucket as opposed to something else? We are in an elimination process here, so you're clear about that.

Dan Vanantwerp
05-31-2018, 06:42 PM
When I use anything to make Cristalica frit it has always been clear/white. The yellow color did not come on until I added black tin, melted overnight and used it the next day. I could see the tint as I gathered but it became very noticeable in the punty bucket. I haven't made frit with it after the tin addition, but I would guess it will look pale yellow.

Pete VanderLaan
05-31-2018, 07:21 PM
well that might just be a nice color. One learns something every day but it will be based in the modifiers and stabilizers. One size ruins all is a good thought. How much did you add?

Dan Vanantwerp
05-31-2018, 10:47 PM
Here are pics of the color change. First is a couple punty shards, before and after tin addition. Other is fragments of a bubble that didn't look good so I bagged it.

Not a bad yellow...

50g/20lb frit. Frit was melted on top of ~20 lbs existing glass.

Eben Horton
06-01-2018, 05:10 AM
that would be a beautiful glass to solid work. looks green to me though...

Pete VanderLaan
06-01-2018, 07:10 AM
Indeed, a pinch of erbium would clean it up... I'll look at the potential of tin to make a yellow but it might be more likely that the existing iron in that glass has flipped valences.

I seems to me that if you are trying to turn an inherently oxidizing glass , such as Cristalica into a reducing glass by overwhelming it with black tin, my question is, Are you trying to color this reduced clear? If you are, the discoloration doesn't matter. If you're trying to make some sort of free flowing clear that takes silvering well, you might consider just getting some SP87 color base. You have to mix it but it has no nitrates in it.

Jim can indeed mix both my clear oxidized and my non oxidized formulas.They fit each other just fine and should fit cristalica but be a bit lower. I can't say about fit with the formula you had handed to you under some table since I no longer work that stuff. I do have this concern that you think my stuff to be low melt material and that's a matter of interpretation. It was designed for Littleton to replace SP87 if the price of Lithium went out of control and that hasn't happened yet. It is high potash which lend itself to excellent coloring and polishing characteristics but potash also tends to make a glass more viscous. I'm quite pleased with it but I suspect stemware makers might not like it at all, unless they like polishing too.

Pete VanderLaan
06-01-2018, 11:26 AM
Indeed, better as a new thread.

Dan Vanantwerp
06-01-2018, 11:40 AM
I can see where it could be called green...sort of lemon-limeish (brand name: limelight).

I was curious about silver chloride accents and read your posts (and Dave's) about it flowing on reduced clear glass. It worked. I never had the silver flow like that before. I gathered over it and seemed like it flowed out between the gathers. Is that even possible? I used way too much. I'm always experimenting and trying to find techniques to potentially combine and find something "unique". For this experiment, I was trying to combine silver chloride accents and chalcedony. The flowing silver overwhelmed everything and I'll have to try again.

It really wasn't very hard to make Cristalica reducing at least at my 6000ft altitude.

BTW silver chloride chunks are available from US pigment for those who don't have a stash of silver nitrate, or nitric acid and a bunch of coins. Fun stuff. I've made silver bromide from Pete's and Henry's instructions and it was a little easier to handle...less chalky. Of course my bromide stuff was very fresh and the chloride may have been on the shelf a while.

I'm hoping to get 100 lbs of your batches from Jim to get a feel for the viscosity and melting. I love the way the older formula works. Thanks so much, Pete.

Pete VanderLaan
06-01-2018, 01:37 PM
you can make your own silver chloride using the directions in Glassnotes 3. Henry hated the way I made silver Nitrate and thought I was a menace to society. I haven't changed. It looks like a mad science experiment when I do it but I hate waiting around. You can also make iodide and bromide from glassnotes as well. With iodide, you can draw on the glass. The sodium bromide and sodium Iodide are what will cost you since they come as a reagent grade. I think Noah handles both.

I always had trouble with Simpson trying to do too many things all at once. He consistently would add all sorts of shit to the Corona formula and frequently made it quite incompatible and rick expected me to fix it. . It was tiring.
No it won't flow between gathers.
Using too much is not a good thing for a variety of reasons.
Learn your basics well first. The silver has not brought you to your knees yet, but it will.
Good Design is way harder than any of this stuff.

Dan Vanantwerp
06-04-2018, 10:07 AM
Went back to a 91 LEC version of Brossphate to make sure I tested it properly. All the tests at 88.6 suggested that I was too low. BUT, the 91 did not fit any better (seemed worse). One last try...gonna take it all the way down to 87.

If that works I'm gonna put a big ol' asterisk next to phosphate opals and fitting other glasses. Weird...

Pete VanderLaan
06-04-2018, 10:30 AM
I run back to your post #15.In that post you refer to the standard E&T calcs and at the same time try to attach actual measured calculations and then refer to 96 color rod measurements. It's comparing apples and oranges.

Reasonably speaking a lot can be learned here from a simple pull test. If you have a bench torch for lamp work, take a cane of each glass about the diameter of a pencil and heat them in that torch. when they're both hot enough to stick to each other, overlap each rod on the other about an inch. Heat them and slowly work them until the have really melted together. Then pull out of the flame and holding each rod with equal pressure, quickly pull them away from each other and hold them in tension until they're cool. PULL STRAIGHT. This may require some practice. Cut the pulled cane in the torch from either rod, the clear or the opal. If over 12 inches of run, there is a gap of 1/2 inch or more measured against a straight surface , it's clearly incompatible BUT the important thing about this test is you can sight down the thread and see which one is on the inside. The one on the inside has a higher expansion.

I don't like this test but you need something here to get you to stop going all over creation with your quest. This test really does work with glasses of similar structure and it can be quite deceptive with dissimilar glasses BUT, it will show you a path as to which one needs work. If you're fortunate, it will get you to where you can do a ring test and that really helps define the adjustment.

Actually matching the phosphate to cristalica should not be all that hard but I think you're making it hard. Stop trying to use E&T if you're going to also compare them to measured expansions as well.

Eben Horton
06-04-2018, 03:06 PM
From an innocent bystander prospective, why not keep adding soda ash to bring the #ís up to the sweet spot? For example keep doing small melts and add say 5% more soda ash until you hit it. Silica if you need to lower the #. Am I missing something here ?

Pete VanderLaan
06-04-2018, 04:05 PM
What you're missing is he doesn't know which way to go. The pull will tell you .

What I'm less than clear about is what size batches are being mixed here. What quality scale is being used? The smaller the batch the greater likelihood for error. Same with the scale. How's it actually getting mixed.

Eben Horton
06-04-2018, 06:10 PM
He needs a dilatometer

Jordan Kube
06-04-2018, 10:12 PM
Why make such a big jump? If one seems low and the other high...

Dan Vanantwerp
06-05-2018, 01:26 PM
I'd love a dilatometer...got $2000? :)

I'm gonna follow my nose on this one. As I lower the LEC, things seem to get better. I was satisfied with the thread tests I ran, but they told me nothing. I think Jordan found the answer with his 87.5 LEC match to Cristalica with the 5% Brossphate. We'll see.

Eben Horton
06-05-2018, 03:17 PM
You can build your own with a gauge from McMaster Carr that measures ten thousandths of an inch and a quartz tube. Presto! Done.

Dan Vanantwerp
06-05-2018, 05:51 PM
I'll look through the Archives for that DIY project. I'm currently walking through them year by year (Yes, my job asks me to sit in front of a computer for hours). There was a lot on that around 2003. Some of you guys have been posting for a long time. I think you have always been one of the more helpful contributors, Eben. For what it's worth, thank you!

Pete VanderLaan
06-05-2018, 06:07 PM
building one is an issue and you have to see it. It's another tool. Sometimes good, sometimes not so good. It takes a village.

Dan Vanantwerp
06-05-2018, 06:41 PM
So, by walking through the Archives I came across Dave's nice description of getting to his first, best phosphate opal...he had not come across the strontium idea yet. This is how he described the compatibility tests:

Now another interesting thing...

I'm working on matching the expansion to 96 and have been using thread pull tests and polariscope. I know that the phosphate and my clear are really different glasses and that a straight thread will not equal a perfect match, but does anyone remember if the phosphate has to test higher or lower to match? I've come 2 points (E&T calculations and equivalent change in the thread))down in expansion from where the final position of the thread shows the phosphate higher expansion, to where the thread is straight, to about one point (calculated) below where the thread was straight. They all show stress in the polariscope.

I also know there are very different overall expansion curves between the clear and the phosphate. When you first pull the thread test it looks like the phosphate is lower than the clear, then after it cools about 30 seconds or more the thread will bend back in the opposite direction quite a bit. That's a lot of change at the transformation point and I know it's the phosphate because this is the only time I've seen that. I've made a few things from each batch and the stuff within about a half point either way from where the thread is straight will withstand diamond sawing and a few other rudimentary stress tests.

I'll answer my own question. The ones that pull straight on the thread test can be de-stressed by coming through the tail end of the annealing process (around transformation point) more slowly."

I'm not sure how I would achieve this tail-end, annealled thread testing, but I really don't want to try anyway. I'm not sure this glass was ever really fit to a "96" clear. I think it's interesting that Dave noted such weird results when comparing theoretical expansion, thread and stress testing. No matter. The stuff is pretty awesome and would be worthy to me as a standalone glass. That I have fit it to Pete's silver opal is really awesome. I'll probably drop Cristalica anyway and focus on a batched clear. Down to my final 2 boxes of cullet.

Thanks for everyone's help in the village :)

Eben Horton
06-05-2018, 07:01 PM
building one is an issue and you have to see it. It's another tool. Sometimes good, sometimes not so good. It takes a village.

If I remember right, your one from the first color class was simply a 12 inch quartz tube with an ID of about 5/16tgs and a 1/4Ē quartz push rod that was about 1 inch shorter than the tube. You would pull a length of your glass that you wanted to measure making sure it was thinner than the I.d. Of the tube and cold work it to exactly 1 inch. Insert the piece in the tube then the push rod and secure the gauge and tare the gauge to zero. Slide it into a small oven and bring it up to 1000 degrees and take a reading on th gauge, which would give you a theoretical expansion reading of 10 thousandths of an inch.

I think thatís how I remember it all working.

Pete VanderLaan
06-06-2018, 07:46 AM
My clear and also my unoxidized batch glasses are a 96. Cristalica is a 97.0. My older unoxidized formula was as I recall in the mid 95's.

The memory of the dilatometer is reasonable short of the brass fitting into which the gauge slips into and gets screwed down. I would not say it was cheap to build nor would I say it's foolproof. It's a tool. It required a very tight kiln to measure in if you recall Eben and without it ( A tubing annealer) it would be a rough go to get tight numbers. It also requires a handheld temperature measuring device. If you recall, I had an omega unit to read the kiln. The test sample in fact was 4mm x 4.000. In all of these tests, they point in a direction. None are foolproof. The goal is to have all the indicators pointing in the same direction. They are the Hagy Seal, the ring test , the pull test and the dilatometer. Doing all of the tests requires experience. If you send material to Corning for testing, They will tell you to always ask for the same technician you have been using. There's a reason for that.

Using Dave's early stuff before the strontium as I recall did use calcium and had the subsequent apatite crystals. Cristalica is an outlier as an expansion. I encouraged Kuchinke to lower that expansion a half point but those guys really never wanted to hear from me about changes in the goop. Switching to mostly strontium did improve things vastly. I think using such things as 20 mule team borax may be a mistake, it does seem to have other things in it. I am going to have Jim mix the stuff for whoever wants it in the west and it will be decidedly different than Cristalica. Melting in a wire melter is not something I've tried.

Dave Bross
06-06-2018, 10:39 AM
A dilatometer does not tell you anything about the variations between two glasses on softening point, which is the point where the glass hardens up from a liquid to a solid.

If one sets up before the other is done shrinking you have a mismatch.

If softening points mismatch, then two glasses testing the same on dilatometer expansion will not fit.

To answer the question about weirdness of thread tests on phosphates. I tried to simulate how many strikes the particular work I was going to do would require. I did these strikes at the stage where the two glasses were melted together (pre-pulling) for the thread test. I shot for having a straight thread on final cooling after doing this and pulling the thread.

Further thoughts...the E&T numbers are most useful after you have a thread test showing how far off you are. In my little world in my style of thread test 1 mm of bend over 200 mm is equivalent to .6 in E&T numbers. If my melt was off 1 mm on thread test I would then go to my E&T calculator and change the ingredients to change the final E&T number .6 for mixing the batch for the next melt or to get amounts for any attempts to add things to correct the melt sitting there.

Using E&T numbers prior to having compatibility proof is just a shot in the dark. If you know what E&T number your furnace needs (each furnace is unique on this) for your clear it increases your odds of coming up close by shooting for that number. Those E&T numbers will get you closer than anything else on the first try but rarely will they hit it.

More fun with phosphate - our side trip into decolorizers reminded me of this - try a tiny bit of phosphorous (less than .5 %) in your clear batch. Brightens it up noticeably. Thanks to Scholes for that one.

I never tried it, but wondered if a tiny bit of phosphorus in the chalcedony wouldn't do something interesting. What it might do is screw it up due to all the oxygen in the phosphorus but maybe not in a tiny amount as in brightening the clear. The "glass within a glass" nature of the phosphate might do something fun.

One more - the yellowing Cristallica actually looks like iron green on my monitor. Could it be iron contamination?

Dan Vanantwerp
06-06-2018, 10:47 AM
I've been a little concerned about the 20 mule borax but really hesitate to change. I checked the MSDS on the stuff and found this a little uncomfortable:


Sodium Tetraborate Decahydrate 1303-96-4 60 Ė 100 %

Now, the 40% difference could just be variable water content in a more or less humid area, but they never go into it. I'm adding about 300g into 10 lbs so any contamination is not insignificant.

I'll get some 5M and give it a shot if this next round is a total head scratcher.

Dan Vanantwerp
06-06-2018, 02:03 PM
Hi Dave, Always glad when you have a chance to chime in. :)

I made sure my sample was struck prior to pulling threads, but it would be tough to try and get it matched to the level of strike for a piece completely worked and boxed.

Have you read the opal phos technical posting put out by Gaffer on their website? They suggest that the bubbles of PO4 continue to grow as the piece is worked making compatibility a bit of a moving target.

In the archives, on a different discussion about compatibility, there was mention of someone working on a piece for 5 hours. Imagine the change in expansion for an opal phos by the time it was boxed if it even made it! Someone else said that opal phos reacts violently with water which I hope you would agree is not true. Pete was a bit skeptical and asked what the chemistry behind that was. I can't imagine what was happening. That you were pre-wetting your batch suggests you took it with a grain of salt. :)

It's like a course in recent (and sometimes not-so-recent) glass history in that section. There is mention of a cad-sel red opal phos. Did that ever get made?

You're probably right about the iron in the Cristalica, but I plead ignorance of the source. That crucible (80lb) has been kept isolated from anything but cullet. Nice to have a redox indicator built into the glass.

I am on the same wavelength as you with merging Brossphate with Chalcedony. I think Pete has mentioned a phosphate based chalcedony as well. I'm taking my steps to get there and learning along the way. One great thing I take with me as a recipient of an advanced degree...I know how to learn, how to be taught and how to teach myself.

Pete VanderLaan
06-06-2018, 02:05 PM
I would not view that as insignificant.

Dan Vanantwerp
06-06-2018, 02:11 PM
That's what I meant. 300g is darn near a lb (453g) so just under 10% of the total weight IS significant.

Pete VanderLaan
06-06-2018, 03:53 PM
How big a batch do you actually mix and melt at a time?
Phosphates shouldn't be confused with typical opals. Opals grow crystals. They grow and collapse and grow again. They rely on Alumina or calcium Fluoride to grow them. Phosphates still need some calcium to work but not to the point of making a bunch of apatite snot. Phosphates have two glasses in solution at the same time which go through an actually separation going from cooled to heated. It's a billion tiny bubbles causing the opalescence, not crystals.

I would have to think for some time about Dave's assertion about mismatch in the cooling process. I don't think I agree with it at all. Your goal is to have two glasses showing no mismatch at room temp after annealing. The pull test is usually a confirmation that neither glass is tugging on each other at that time. That's true of the Ring and the Hagy as well. I can see wanting to attempt the strike on the opal when drawn as a clear as well as after the phase separation occurs. I would find that info useful.

Dan Vanantwerp
06-06-2018, 05:01 PM
10 lbs. My color crucibles are 17 lbs. I am able to get 6-8 lbs charged before my first blow session Saturday and then top off with the rest for Sunday.

Pete VanderLaan
06-06-2018, 05:28 PM
I don't do color tests under 20 lb mixes because I feel the potential for error at the scales gets too big. That number you just gave for the 20 mule team borax just grew to be a monster.

What is you scale that you use for everything??

Dan Vanantwerp
06-07-2018, 10:19 AM
Recall that the majority of my mixing has already been done by Jim. I am just adding borax, phosphate and sand. My scales are all digital. I'm on the lookout for something analog, but these are working well. I have tested them with controls.

Just added some 5M borax to an existing order at the pottery supply store. Should have just waited to get some but I got impatient and Lowes had the 20 mule.

Dave Bross
06-07-2018, 06:31 PM
One other thought.....the lower percentage of phosphorus as in the original recipe will probably give you less trouble on expansion matching. That smaller amount gets pretty dense if struck a few times.

Dan Vanantwerp
06-07-2018, 10:55 PM
Hi Dave, I'm hoping this thread helps anyone else that might want to get into the Brossphate craze so I'm glad you brought the density up. I think the 2.5% is ok but at 3.2% I can really get a solid white. I was getting a fairly patchy effect down lower. In practical terms, multiple reheats just to strike the color really ups the time to make a piece of glass and time is $$.

I would say that my melting technique has gotten better so now I might get a better white at a lower %. Man, the 3.2% is nice though...starts clear and over a couple heats fades to that solid, wet white :) I think it would also still be possible to get the veiled effect you and others have discussed with less strikes or perhaps a thin strip gather.

Just charged with my latest mix so we'll see if I guessed right and can get a match to Cristalica. I have a match to Pete's older chalcedony recipe at 88.6 LEC. It was still pretty off from Cristalica so I dropped it to 86.5 LEC for this test.

A great example of A fitting B, B fitting C, but A not necessarily fitting C.

Pete VanderLaan
06-09-2018, 07:01 PM
10 lbs. My color crucibles are 17 lbs. I am able to get 6-8 lbs charged before my first blow session Saturday and then top off with the rest for Sunday.
If you are using 10 lb mixes, if I understand that correctly, and you are adding around 300 grams of material to a mix you say Jim at East bay has already mixed, and you suggest it is mostly mixed by east bay, I think you're wrong. What I do think is that you're adding about 8% new materials to Jim's stuff in various semi hostile forms. In my mind, that''s a very large number. so, again, how are you mixing this new stuff in? What is your mixer?

Process is key in doing this stuff.

Dan Vanantwerp
06-10-2018, 11:39 PM
New recipe based on a 86.5 LEC worked perfectly for both the Cristalica AND Chalcedony glasses. Seems this stuff really wants a relatively low theoretical expansion to match a "96" glass just as Jordan suggested.

I performed the ring test with inside and outside applications. I was surprised enough when I opened the annealer to find everything intact. To pass the ring test with flying colors was hoped for, but really unexpected.

Going to repeat the formula in a larger scale and see if it passes a second analysis. Strangely, this mix seemed to strike a bit more quickly/easily than the previous mixes so I'll see if that remains consistent.

Pete, I'm doing my best to mix in a little food bucket I got at the restaurant supply store. They actually make a strainer that fits right on the top of it. I bought the lid and do some hard shaking, rolling and turning. I have thought of trying to secure it closed and place it in my cement mixer for a while. I've also used the drill mixer method but I don't think it's as thorough as what I've described.

Pete VanderLaan
06-11-2018, 06:12 AM
I am glad you are getting a fit. With the mixing you describe, I kind of doubt your results will be consistent. When I do a color additive using my clear that Spruce Pine mixed for me, in 14 lbs, adding seven grams, it goes back in the cement mixer for a half hour.

Dave Bross
06-12-2018, 02:50 PM
Get yourself a drill driven paint mixer, preferably plastic but steel works fine. The steel ones eventually eat up the bucket.

This will mix it up REALLY well and make you feel less like a performing monkey rolling a bucket around.

You can fabricate a dust cover for the bucket from plastic, cardboard, or whatever. The commercial ones look like a shower cap for someone with a head the size of a bucket and a hole dead center for the mixer shaft.

I just take it outside and wear a respirator and gloves.


Dan Vanantwerp
06-20-2018, 01:31 PM
The results repeated with a new batch of Brossphate. Under my conditions, a theoretical expansion of 86.5 is the target. I've started making pieces with layers of Cristalica, Brossphate opal and Chalcedony with nice results. I'm about ready to try some colors, in addition to the white.

Just as Dave described, the glass can be made more opaque with additional reheats. It is worth taking an oxypropane torch to this glass to watch the waves of opacity form. I believe this is how Dave uses the glass and I didn't quite grasp what he was describing until I looked at it this way. With a torch and air gun (heat-cool cycles) the deep opacity can be coaxed out very easily. I was even able to get just a small section of the piece (the lip) to go deep opaque. Poor man's lip wrap :)