This glass varies from 7mm in thickness to 15mm. Due to this variation I have to fire the glass in the kiln for a long time to ensure it anneals properly. (The term annealing is a process that we put the glass through when cooling it in the kiln. This removes the materials internal stresses, making it stable once out of the kiln). Depending on the scale of the heavily textured pieces they can be in. the kiln for a number of days.