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Doug Sheridan 05-29-2012 02:08 PM

Spectrum Premium Nuggets: Corrosive or not?
It seems that Spruce Pine will not have their cullet furnace hot for a few months, and I've not heard or read about the premium nuggets for some time. Did they work out the 97.5 issue, and does it eat furnaces like the regular nuggets?

Scott Novota 05-29-2012 02:59 PM


After using about 3000lbs of the spectrum 96 old nuggets it did one hell of a job on my furnace. Basically a full rebuild from the ground up.

I switched furnaces at this point and started using the new nuggets and had gone though about 4000lbs of the new nuggets with no real problems at all in the new furnace. Normal wear and tear no visible problems like the old nuggets at all. I had 1000lbs of the old nuggets left and did not want to waste them. This was a huge mistake. They did 3 times more damage in 1 month than the whole previous 4000lbs of new nuggets over a year period.

In short, and only based on my limited experience, is that the new nuggets do not do the damage to the furnace the way the old nuggets did. I just ordered anouther 4k of the new ones and will never ever go back to the old ones.

Take anything I say with a grain of salt as it is only from my personal experience.

Sky Campbell 05-29-2012 03:23 PM

I just wish they would make premium nuggets compatible. I make a line a production dicro implosion paper weights and after two days of losing 60 to 70 weights I gave up. The premium isn't even compatible with the system 96. I know because the dicro I use is all coated on system 96.

I have never had a problem in blown ware but then again I don't make thick chunky stuff. I would still like them to revist the comparability issues.

Barb Sanderson 05-29-2012 06:54 PM

I'm with Scott on the corrosion question. I switched to SPectrum Premium in January this year and have not had any corrosion issues since switching over. I haven't had any compatability problems either but I don't do heavy weights like Sky so I can't really say. There is another recent thread about this somewhere here and I believe the corrosion issues with the other SPectrum nuggets was due to borax.....right Pete?


Mark Rosenbaum 05-29-2012 09:35 PM

Hey Doug:
Did SP give any indication on when they will be hot and producing again? Have they even started building the furnace? They told me in Jan that they would be up and running in June/July....

Pete VanderLaan 05-30-2012 06:15 AM

The Steel work is done, courtesy of great work from Lawrence Duckworth. Charlie is finalizing the AZS liner stuff, which is the slow part. I think we'll see glass by Christmas. I would be surprised if it can be faster than that. It's quite the beast.

My belief about the borax which, keep in mind is a mix of sodium and boron, is that is that it becomes a dissolving catalyst when combined with barium in any glass. I cannot prove that but I've seen glasses that contain both before and they have all had this problem. I believe the nuggets are very close in formulation to the early Crystallica glasses that came out of Europe. Barium really loosens a glass up but most people use it for brightness. Couple that up with the effect that Borax has of both softening while maintaining Linear expansion pretty much and you have a material that is very fluid and can really get into the spaces between the tabular alumina grains in the pot. Frank Wooley used to say to me that no one glass is more corrosive than any other and that it was just a question of viscosity at any fixed temperature but this stuff seems to prove that generalization incorrect since the stuff seems to attack everything made of silica, alumina or fireclays. It reminds me of my fluorine melts is its aggression. SP87 does not contain borax but it does have barium and it is simply not reactive with furnace parts in such an aggressive way.

What seems to me (and I'm making an educated guess again,) makes the spectrum nuggets so corrosive is that they haven't actually completed the chemical reaction from being melted. They are still gassing off. So, when they get put in an electric furnace with no vents the furnaces , it's a recipe for dissolution. At the very least the furnaces need to be vented and none of the electrics were designed that way. Comparatively, electric furnaces are a fairly recent step in evolution and it just wasn't anticipated as a problem.

I recently rebuilt the door on mine and installed a vent and it's remarkable how much crap comes out of that hole in the form of yellow crystalline stuff. I plug the hole when I'm not charging. My glass formulation does have Borax in it although very little, 1.65 lbs in a 78 lb mix but it contains no barium. I don't have trouble with it beyond the pot slowly dissolving which is a cost of doing business.

Lawrence Duckworth 05-30-2012 01:44 PM


Originally Posted by Pete VanderLaan (Post 105453)
The Steel work is done, courtesy of great work from Lawrence Duckworth. .

Spruce Pine N.C. is a gorgeous part of this country and Tom Littleton is a great guy to work with. I got a tour of the shop and how batch is made and seen the huge color inventory too, and he also gave me an inspiring book, Harvey K. Littleton a Life in Glass.:)

...turns out Tom Littleton is the son of Harvey Littleton!!!....who new?!!

Pete VanderLaan 05-30-2012 05:30 PM

I new... or (knew). I heard some very nice reviews of your steel work Lawrence. Good job. I'm glad I could recommend you.

Thomas Chapman 05-30-2012 08:32 PM

back to nuggets
It was nice to enjoy most of the properties of the famed Spruce Pine over the last year and a half...what with melting the SP chips cullet, some w/er, some w/ Texas Sand, et cetera.

I have now melted 4 different cullets in my seven-year-old invested & recuperated pot: CBG (Seattle Batch's Chinese campaign--later abandoned) after build [endorsed by Dante, Lino, Sonja], then spectrum 96 nuggets, then Spectrum premium nuggets, then SP Chips.

Switched from original (96) nugs to Premium due to corrosion observations here and elsewhere (participants on this board). This issue is not that major in gas fired units, I think.

I do not make all that many paperweights but seeing them check after polishing was quite annoying with the premium (l.e.c. ninety-what?) nuggets. I do make some polished sculpturals and some pendant lights. I would rather live with maintenance issues (clean the stack, patch the door) than with the incompatability issues.
That's all for now.

Pete VanderLaan 05-31-2012 05:25 AM

I am supposed to issue a disclaimer here and say this is my opinion: I can substantiate my opinion.

I keep hearing issues about the expansion of the premium nuggets and how they just don't really fit. The story is strange and I have held off on it for some time. When I sell pots, I hear stories about the issue and when I hear stories again and again, I start to pay attention. People are having issues with compatibility at the premium product. I wish they weren't. It is always possible that annealing comes in to play but I would expect that to be an across the boards issue.

The claim was made as I best understand it that Spectrum obtained different batch samples of Spruce Pine 87 in the Seattle area and melted them.They then produced the premium nuggets to match the obtained SP samples. They then sent the samples down to John Croucher at Gaffer and John looked at them. They showed a 97.5 expansion. When Croucher asked why they made the glass a 97.5, they responded that they were simply matching Spruce Pine. John was not a happy camper since he has modeled after a 96 linear expansion glass and wants a consistent American model to match. He and I have talked about that quite a bit. John felt that Spruce Pine had changed over the years or Spectrum would not have done what they did. I would note, and I think it's important, that to the best of my knowledge John only had a sample supplied from Spectrum. He never asked for one from Spruce Pine.

Now at that time, there could only be a few things making the SP87 glass switch dramatically. The first would be an actual change in the formula which made no sense. Tom told me he had not done that. The second would be raw materials supplied with moisture retention issues and the third would be errors at the scales. It struck me that the second two would also affect the mixing of Gaffer batch done at Spruce Pine, so I asked John if he had tested his own batch coming out of the plant for a switch in expansion. If one was off, it stood to reason that the other would be off as well. I never heard back from John about that.

Tom Littleton hired me to run expansion testing on his product, which I did. I obtained samples from three studios of the actual glass from recent batches. I tested them against some five year old samples of Spruce Pine which I keep for moments like this. I found them to be identical in every way. Nothing in the Spruce Pine had changed. Tom had changed feldspar suppliers but it had not affected the final product and I did check the chemical analysis of the spar.

This would all be a "He said, She said" except that I keep hearing about compatibility issues with the Spectrum in thicker work, I have multiple sources for those assertions in particular. The observations made by Sky Campbell are typical. I have others. Inclusions of Uroboros 96 dichroic break up in weights made from the premium stuff. This does not happen apparently with SP87 so I really have to come to the conclusion that my observations about SP not having changed are correct. My test results for the SP87 actually put the expansion on SP87 slightly under 96. The premium nuggets at 97.5 is, in my opinion is on the outside edge of an acceptable fit with many commercial colors. I would note that I have never tested the Premium nuggets and am relying on the factory specs. In my opinion, it would not be difficult to move the expansion on the nuggets closer to a 96.

This should not be construed as a recommendation about any of these products one way or another. It's not. It's just my best understanding of what they are.

This has no relation to the issues surrounding the Spruce Pine Cullet. That was a quality control issue at the Fenton Plant where the melting was taking place. Because those issues could not be resolved, production ceased and will restart in the near future with all processing being done in house in North Carolina.

Anyone from Gaffer or Spectrum is welcome to chime in here. I would love their perspectives.

Lawrence Duckworth 05-31-2012 08:34 AM

thanks again Pete for the recommendation, I know doing that kind of thing can be pudy risky, especially with glass blowing types. I may not be known as the godfather of studio glass but for everyone here and those that follow its great knowing that all will honor me as the one who gave studio cullet glass Structure and Foundation.

have a nice day people!:)

Pete VanderLaan 05-31-2012 08:59 AM


Originally Posted by Lawrence Duckworth (Post 105536)
thanks again Pete for the recommendation, I know doing that kind of thing can be pudy risky, especially with glass blowing types. I may not be known as the godfather of studio glass but for everyone here and those that follow its great knowing that all will honor me as the one who gave studio cullet glass Structure and Foundation.

have a nice day people!:)

You'd better hope!

Robert Gary Parkes 05-31-2012 11:31 AM

I have been using S96 regular nuggets for about three years, in a 200# moly melter, I am just starting on my fourth ton. I have no door vent, however I do small charges over a 24hr period, and vent the chamber by opening the door between charges for a few moments, I have no evidence of corrosion, any where. I have a slight build up of yellow fluff on the top of the door arch which i remove, at my last cleanout my pot looked very good, I never fire my furnace over 2000 F. my glass is clean and bright. it may take an extra day to fine out. but low and slow is the way to go.

Michael Mortara 05-31-2012 01:55 PM

Worked with the 96 for many years, never a fit issue. Had the furnace eating issue, but that was when we were electric, since switching to gas fired, no problems. Tried the premium, had many fit issues, all in our cut/polished solid work, Olympic said they tested the colors against SP and the Premium (done at spectrum though) and all fit/matched, which of course was BS and pissed me off. Back to the 96, which has been very consistent over the years and bullet proof for our solid work with both Reichenbach and Gaffer...

Sky Campbell 05-31-2012 02:15 PM

Ok Lawrence pics or it didn't happen.

Just kidding but really where is the blog?

John Croucher 05-31-2012 05:50 PM

This whole saga with Spectrum cullet has been a big disapointment for Gaffer. When they first brought out their System 96 nuggets we were disturbed to find out that they were about 2 points lower than our standard which was tuned to SP87. I took the trouble to fly to Seattle and meet with their people about 7 years ago and plead with them to match the defacto standard in the US glassblowing scene which was SP87. They wouldn't do that because they were already heavily invested in their System 96 gig, even though their sheet glass standard was irrelevant to 99% of glassblowers.

Anyway last year out of the blue they released their new Premium nuggets. They announced that the new nuggets wouldn't be compatible with the original System 96. Hooray we thought, maybe they have finally got it on the money with SP87.

Unfortunately our tests showed that rather than moving their expansion up a couple of points they had now jumped it 1.5- 2 points higher than SP87.
As Peter has explained they claimed that this was based on sample SP batchs they had bought in Seattle.

Naturally we then were freaked out that SP had changed so got in touch with SP to see if that was the case. (Cont)

John Croucher 05-31-2012 06:20 PM

Cont> Tom Littleton was able to assure us that apart from a change in a feldspar source some years ago (with virtually identical specs to their original feldspar) nothing had changed. Pete V double checked with old SP as he outlined above .

We melted the SP 87 recipe at our factory and trident tested it with our standard just to make sure that we definitely were on the same page. The tests confirmed that we were. We sent the SP87 recipe to Spectrum so that they could repeat the same experiment rather than rely on samples gathered in Seattle.

I'm sorry to say we have heard nothing since. A local glassblower has just taken delivery of a couple of tonnes of Premium nuggets and they are still 2 points higher than our standard and SP87 so nothing has changed.

We desperately want Spectrum to make a cullet that is compatible with that defacto standard in the States which we have tuned all our colour to. We accept that defacto standard is SP87. If they do we will be the first to shout about it from the roof tops.

Pete VanderLaan 05-31-2012 06:36 PM

John, what I fail to understand in all of this is why Spectrum seems so committed to making something so out of the mainstream. You know as well as I how easy it would be to move the expansion coefficient to a 96. Putting the expansion only on the website seems odd to me. It should be on the bag. I recognize that you aren't a spokesman for Spectrum but perhaps you have some influence. I'm sure I don't. I'm not so sure Tom would want his formula sent to his competitor though, if I understand you correctly about that.

I also still have issues with the original samples sent to you by Spectrum that were alleged to be SP87 which you have already heard from me about.

John Croucher 05-31-2012 07:08 PM

I don't get it why Spectrum won't listen to the industry they are wanting to serve.
They are relatively recent entrants into the glass blowing scene and one would have thought they would want to carefully canvas expert opinion before they offered their product. To put out two cullets, neither compatible with each other (which they advertise) and neither compatible with the defacto standard of SP87 defies logic.

SP gave their recipe to me on a handout they gave anyone that asked in 1989. At that time I believe the recipe was public knowledge. I gave it to Spectrum in the obviously naive belief it would benefit them to have a yardstick they could measure their product specs against.

Pete VanderLaan 05-31-2012 07:10 PM

I remember when Tom did that. I don't think he would do that today. Just guessing.

Pete VanderLaan 05-31-2012 07:22 PM

Melting SP's formula would only help Spectrum in a limited way. It would have to be melted hotter and longer. It would need to be melted in the end users furnace hotter and longer as well. Materials used are still based on shipping costs from mine to factory. I don't know what is and isn't attractive there. I would think that the end product would have to cost a good deal more than the current Spectrum products for the aforementioned reasons. The SP chips were totally fined out as a product which made melting in the studio a total dream. The Spectrum nuggets had yet to complete their chemical reaction when they hit the end user which is a good part of the corrosion issue.

Mike Hanson 05-31-2012 09:49 PM


Originally Posted by Pete VanderLaan (Post 105558)
The SP chips were totally fined out as a product which made melting in the studio a total dream.

Maybe the ones you got were but, the ones that I have received
(especially lately) still need to be fined out. There are bubbles noticeable in the chips right out of the bag. I like Spruce Pine to work with but, the chips need some work. Like many have said, there is no free lunch. I hope the new method of production for SP chips will be good for us end users.

Michael Mortara 05-31-2012 10:12 PM

My experience, and I have been through 20 tons of nuggets, is that the corrosion issues are primarily in electric furnaces melting system 96.

The premium nuggets do not seem to have the same issues in that regard, but have their own, in my opinion, more detrimental issue, of compatibility.

Pete VanderLaan 06-01-2012 05:04 AM


Originally Posted by Mike Hanson (Post 105559)
Maybe the ones you got were but, the ones that I have received
(especially lately) still need to be fined out. There are bubbles noticeable in the chips right out of the bag. I like Spruce Pine to work with but, the chips need some work. Like many have said, there is no free lunch. I hope the new method of production for SP chips will be good for us end users.

As I said: "Production issues at Fenton could not be resolved so production ceased. " The fault lay with Fenton Glass sadly. Those chips made right are really nice.

As to Mike's comments about the corrosion, getting the boron out of the nuggets when in the presence of barium did alleviate the problem. It always will. Robert Gary Parks is doing OK with the regular nuggets because he melts so cold. It's not a viable option for most people but it does dramatically slow down the microgram release that occurs at higher temperatures which Durk Valkema has so amply measured.

What I find fascinating is John Corucher's assertion that the original system 96 nuggets are in fact a 94. I have never tested them for actual expansion, only relative strain to a few other glasses. I don't understand this company.

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