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I did some test tiles using clear OceanSide 96 with Youghiogheny, Wissmach, and Oceanside colored transparent. I used the two polarized sheets on a light table to see if there were any incompatible pieces. The Shamrock Green Youghiogheny looked to be the only color that was incompatible with Oceanside clear. There were a few other Youghiogheny colors that looked to be compatible. Is this not unusual to see one color be incompatible while other colors are compatible?

My firing schedule:
600 1020 30
AFAP 1460 10
AFAP 900 45
100 700 10
300 100 off

Thanks for any information,
Molly

No it's not that unusual when using glass from different manufacturers, even though they are supposed to be the same COE. There are other factors that determine compatibility, that could be explained better by others. Even some glass made by the same company with the same COE can show incompatibility, for example Bullseye white can cause incompatibility with other Bullseye glasses ( unless they fixed it by now). This is why we test before a project, in the long run it saves time and glass.

Compatibility can be a strange thing. There are some glasses that actually change their COE as they are heated and reheated. When I was blowing furnace glass there were some glasses that would shift by as much as 6-8 points the longer you worked them. I also know of many paperweight makers that have used all sorts of COE glass in their weights and they have been intact for many decades. Many times viscosity will play a very important part in the compatibility of different glasses. Dan Schwoerer of Bullseye has written some very good articles on this and I think they are posted on their website. In other words if you are looking for absolutes, I would suggest another media besides glass. It can be very fickle and frustrating but also very satisfying and addictive.