California glass expert performs a root cause failure analysis on a failed tempered glass pot cover. The pot cover failed “spontaneously” in the users home, and the handle with captured glass was submitted to the California failure analysis lab for evaluation. The failure was caused by the interaction of the handle hardware (i.e. cup washer) with the tempered glass. Crush damage from the cup washer that caused the failure. The series of photo micro graphs above demonstrate the findings. The lesson to be learned here is: there should be no glass-to-metal contact with tempered glass. This type of contact raises the probability of failure. In the case of tempered glass the failure appears to be spontaneous.