Question: What is Coefficient of Expansion and how does it affect fused glass jewelry?
Answer: Coefficient of Expansion (COE) is a term the refers to how glass expands when heated. As glass heats inside a kiln, it isn't sitting still. Though it may look like it's just sitting there, it's actually contracting and expanding. Since fused glass is dealing with layers of glass, these layers are moving together and trying to figure out what to do. They want to squish together. However, if their COE doesn't match then they have trouble with this and eventually will break apart, thus cracking and ruining your jewelry piece. So, it is crucial that all the glass used for the same piece being created have the same COE. Thanks to manufactures that know how to test for COE, we are provided this information when we purchase glass. The Bullseye Glass Company, for example, provides glass with a COE of 90. This is the industry standard. However, not all fused glass has a COE of 90, so you always need to check before mixing different types of glass together when making fused glass jewelry.
