You dont say what went wrong. I have tweaked Bullseye schedule using much slower ramps. IN fact for 3″ I used the 6″ schedule. The first 2 seg need to be really slow (Thermal shock) but if its not that I found the longer i annealled the better with transparent. Never done opals so dont know.
Glass once it begins to flow fully at 1450 & above will just about stick to anything so a ‘release agent’ of some sort is required. Kiln wash, firing paper, boron spray etc. So its not so much the temperature the mold can withstand its the sticky glass! Even stainless steel molds need release agent & its melting point is 2750.
I use kids plasticene. I make a worm larger than the hole to be drilled & stick it in a circle to the glass. Then I fill the well with water. Done it that way for years. I now use diamond holes saws up to 2″ rather than a circle cutter. Tip- pressing the plasticene on the glass dry & it when your srilling it leaks just press it until the leak…[Read more]