Many reasons can cause the glass to break during a repair.
If a crack is in the glass from an original break, it could grow and cause more of the piece to crack. This can happen just from heating up in the kiln.
Sometimes welds are not as good as we hope, and when this happens the blower has no control over how the piece to be repaired will react to thermal change.
Sometimes the blower runs into a scenario they have never seen in glass and do not know how to fix the piece. This can happen during the repair that maybe the blower could not foresee. Elev8 Premier has a team of blowers look at the glass before any