Normally, I sandwich the powders, frits & confetti between two pieces of glass ranging from sizes 10X10 to large pieces. Recently the powder in between the glass at temperatures at above 800C forms spider web cracking. Not the glass, the powder only. It happens severely with the Amber which also colour distorts, and to the opaque white. The cool colours are OK. My problem is, is that reducing the temperature the edges do not fuse properly. Raising the temperature I have fused edges but cracked colour. This all began since the lead was banned in Europe from being manufactured in the product. I never had a problem before.
I have been using OPTUL IRIS ARC 82+/-3
Can anyone help with my problem?