Is there a limit to how many times a piece can be full fused? We have a customer who has worked on a piece (a mask) approximately 10x16" BE double layer irid transparent with elements of frit and dicro; after each of 3 full fuse firings, she decided to add more "decorations" to it; including firing over fiber paper cut into designs (bas relief), adding additional frit, etc. The piece fired successfully until the fourth (and last) firing, where the piece was slumped over a large platter(which was lined with thin fire paper). I used a very conservative firing schedule, which I can send if necessary. (I did not exceed 200 degrees per hour on the ramp up; top temp was 1220 degrees in a skutt glass kiln with side elements. My first questions, tho, is does the glass tend to "weaken" upon multiple firings? or change its coefficiency? Do the additions of copper wire in between layers play a role in disaster upon slumping?
Thanks for any input!!