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Old 04-14-2019, 01:31 PM
Louis Copper Louis Copper is offline
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Join Date: Apr 2019
Location: Evanston (Chicago) IL
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Thanks for the follow-up guys.

Shawn, I get your point about mass; with the glass itself, the molds and the kiln furniture to support everything, the controller is often waiting on the mass to cool… and times are prolonged at bad places in the heat cycle. No matter what I do, prolonged time at temp has to be taken in stride by the glass I use.

So, unfortunately, the use of Spruce Pine blowing batch for casting probably goes in the ‘Lou’s Folly” category… and rather than try to make a pick-up out of a sedan, I should go find a pickup, or something framed for it.. If glass recipes were that robust, people wouldn’t have to fine-tune them for their particular use like they do.

Years ago when I was slumping and using mostly BE sheet, I saved every sheet scrap, because it was implied (or not explicitly denied) that all those scraps could be useful casting material. Just recently, though, I asked the direct question is the batch for their billets the same as the batch for their sheets…. They did not answer… so I am thinking they are indeed different. You can see differences when you cast with sheet scrap Vs billet, but it is easy to attribute the differences to the form and trapped air, higher surface. But there is also more veiling, and visible flow lines with some colors… i.e. de-vit, perhaps.

Spectrum 96 had casting rocks in the old days, and clear casting plate. The rocks were produced by Uroboros, and the plate by Spectrum. I actually had good results with the plate, and bought quite a lot of it. All that came to a halt when operations ceased in Portland. I am really thankful that Oceanside came along and bought Spectrum, but so far the consideration for casting glass has been on the back burner as they ramp up and catch up demand for sheet, frit, stringer, etc. The plate was actually continuous ribbon made, with the thickness adjusted to about ½ inch. I am also thinking that they are doing some market review, trying to see if casting glass is worth doing… not sure though. The price point of Gaffer and Banas (Czech) and Bullseye seem to invite competition though. I pretty consistently found Spectrum more resistant to de-vit than Bullseye for casting, and I have had others tell me the same thing about fusing.

One of the reasons we tried to cast with Spruce Pine is that, if our sources of less expensive casting glass dried up, then it would be a way to keep working. Gaffer is lovely stuff, but if you make medium to big stuff, you can have hundreds of $ in one piece. Even with all our dinking around we made some beautiful SP colors for $3 a pound… so we had to try.

I get you about casting a sphere too.. blowing a bubble makes a lot more sense for round… but we planned further processing, cutting and polishing, as one part of a larger assembly, and solid was needed for that.

Pete; there are words to that effect on the GafferUSA website… that they developed the batch as a representative middle-of-the-road formula for their colors, reasoning the colors would thereby be useful to the most people. Casting was not on their minds or at least was not mentioned.

Spruce Pine helped me out when I wanted 100 lbs of their color base. It is a real hassle for them though, their weighing equipment is made, as you say, for large quantities, and 100 lbs is about the least they can measure out. And as 100 lbs is too big for UPS, they split it into 50 lb bags, some ingredients in one, some in the other… not normal. They have to bag it after weighing, not where they normally do which is after large scale blending, so that is a weird equipment arrangement and extra handling. They have to charge extra just because of all the labor to screw around like this. Tons of product actually requires less labor… one guy only at bagging for example… I would like someday to try your formula, but I think a more reasonable approach would be to wait for the next big batch order to come in, and then piggy back on it… So if you or someone wanted 3000 lbs, Spruce Pine could make 3300, and have 300 to sell to me. Right now I want to run some tests. You like/developed it for blowing and have had good slumping results as well, and it sounds good. I would like to try to carry on my color testing and casting with it as a new basis. What is really good too is the blowers we share space with might like it too, and then we could have a raw material useful to all.

Now that you say the name Labino, it rings a bell. And now that I am aware of Buddha’s feelings on the matter, I am a converted believer in keeping him happy too.

I heard your point about equipment corrosion with the boron, and perhaps problems difficult to unravel when it is present. Is it bad for other reasons? Our color and comparison tests so far have been in an electric kiln in small crucibles, so perhaps the CaF2 should be tried in the gas fired furnace later.

John, thanks for the reference about Alumina… I will request it.

Thank you all for sharing your experience. Now I have some ways forward I had not thought of, and am not dead in the water. Lou
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