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Old 04-15-2019, 12:09 PM
Louis Copper Louis Copper is offline
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Join Date: Apr 2019
Location: Evanston (Chicago) IL
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Hello again. And thank you again for your continued conversation and thoughts about this.

You all have such a different angle on glass than I, and greater depth of understanding along the whole chain from formulation, to fusion, and then to use. I came to working already-made glass bought from a few limited suppliers and then forming it in a kiln. Our conversation exemplifies just how narrow a slice I have been focused on. (I have never really done blowing either, as it frightens me.)

I am not really a proponent of anyone’s glass and did not mean to sound like I was. I have found that some glasses are better suited to specific projects/techniques than others.. I have often wished that I could make my own color just so I could have more range of colors and densities… of course without realizing the full implications of doing my own formulation of batch… a whole art/science in itself.

You guys made a great point about crashing the kiln, and we just have to be wiser about scheduling so we can be there to do it… it is worth the trouble, and we have ignored a step we can take by assuming it not to be significant.

The Spruce Pine people really emphasized that I need to mix color base well, and thanks for that point. I will take extra care with it. I hear about the fining oxidizers, and I will see it I guess. I can add some Sb oxide if the fining is poor, but first thing is to check the color base alone. We are trying some commercial crucibles made with different formulations to see if any color is leached out of the crucible… in order to find the one most inert to color. the WER formula is made to reduce its sensitivity to colorant impurities.. iron mostly I gather… so we asked for the color base to have a more sensitive indicator.
I get your philosophy of spending more to get the better result, and am in camp with you on that. If I can pick a better batch to work with, I am happy to pay the higher price for it.
I did not take what you and John said as being different, just as different ways of referring to the same guideline/rule.

I have a take on suckers… my understanding is that a certain set of circumstances are needed for them to form. If you have a mold with a contiguous built-in reservoir, and the volume of glass is a bit excess, then when the mold is full there will be a residual level in the reservoir. The trouble arises when the top surface of that ‘casting pool’ in the reservoir solidifies before the interior glass. Because of thermal contraction, if the casting is contiguous with the reservoir, then as the whole mass cools, it must contract. If the casting pool is ‘frozen over’ and it cannot contract from there, it will pull in somewhere along the mold wall, usually at one of the warmest spots remaining in the assembly, as that is where movement is easiest.
This is exacerbated when the freeze over happens with a very large temperature difference between interior and frozen surface, as contraction is greater the greater the difference. So this is actually a reason not to dump the heat, if doing so causes your reservoir to become immobile.. Part of the reason for the recommendation to hold at 1200F is that will help reduce the difference in the two temperatures. Other people cover the reservoir with a fiber blanket as the heat is dumped so the reservoir glass doesn’t get way ahead of the rest, and the molds and furniture have a chance to cool more too. One of the things about the flower pot or any sort of separate reservoir is it is no longer a confined and contiguous piece of glass. Any way, I got this idea from one instructor I had a Corning, and it makes sense to me.. you can take it for what its worth… clearer than the BE explanation, for sure.

I see your logic about the price of casting glass. Oceanside is an unknown since they haven’t begun to work on it, and have a smaller color selection than BE in the recipes they purchased from Spectrum and have a lot of development to do to approach the color range of BE. And I think they inherited quality problems from Uroboros (who had de-vit issues) and Spectrum (who had stone issues). I hope they don’t stop production altogether though, if for no other reason than to keep BE thinking. If I had the money I would consider buying Gaffer only, and make more work and do less tests. Even as I say so, though, I know that the color tests I have done have taught me so much, that it was well worth it, despite some money down the tube for glass I can’t cast.

It never occurred to me you were talking about making a solid orb on a pipe… a symptom of my inexperience there!

thanks for the clarification of the rule, and for the article. I think you confirmed the common basis. I hope to read that for whatever background understanding I can glean from it.

I will be out of touch for an out of town trip, and wanted you to know I won’t have access while I’m away. Not that I’m expecting any kind of answer beyond what you have already given, but just so you know if I go silent for a while. You have been most helpful, and I have many things to ‘go forth’ with, and the thread can end now if it's time to move on. Thank you for sharing your knowledge.
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