As a glass manufacturer we take great care to provide a product that is suitable for all kiln forming artists. We work with the best experts in the field. Many of these experts are the same people who work or worked with other glass manufacturers to develop the right glass for fusing. One of the main indicators for compatibility are still the stress marks when glass is tested against the crystal glass of the COE in question. 

The picture to the left shows Wissmach

90-13 Dark Red 

tested against Bullseye Clear. As you can see, there are no stress marks at at all.

To demonstrate what it would look like, if it were not compatible, we fired the same Wissmach 90-13 on to a piece of 96 Clear. The white spots around the red are indicators of stress. 

Yes, there are other components that can cause cracks, like viscosity and changes at excessive temperatures used for pot melts and float casting. That is why every glass company recommends a test firing before you dive into the final big project. We here at Wissmach will go a step further and will recommend a test firing under the same conditions you plan to fire your final piece. Especially for the warm colors, like red, yellow and orange, which could shift a point or two when fired very hot and held for a long time. 

Here at Wissmach a sheet of kiln glass does not leave the factory without being tested for regular fusing projects and temperatures. And if there is just the smallest sign of stress, we integrate it into our huge line of stained glass and do not sell it as Kiln Glass.

Also have a look at a previous blog entry.