View Single Post
  #10  
Old 05-31-2012, 06:25 AM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 21,506
Pete VanderLaan is on a distinguished road
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.
__________________
Where are we going and why am I in this basket?
Reply With Quote