Glass failure analysis expert demonstrates how to locate the origin of a tempered glass failure. Glass failure analysis of a tempered glass piece is difficult (if not impossible) because tempered glass fracture results in many small pieces. In many cases the glass failure falls apart and there is no pattern left to trace to the origin. The photograph above provides a pattern that can be a useful tool for locating the general location of the failure origion of a partial crack pattern. In the above example a glass expert taped a tempered glass pickup truck rear window with transparent tape and impacted it with a simulated human head. The resulting crack pattern is preserved. The impact point is the center of a “web” of cracks. The predominant pattern is a series of “spokes” eminating from the impact point which is also the failure origin.