Impact Marks in Glass

JSGT 1946 V30 T239-T242

The grey mark caused by glass-to-glass impact is shown to consist of a large number of microscopic flaws, the pattern of which is the same on both members subject to the impact. The origin of the flaws is not understood fully, but the result of the impact is a permanent rupture of the surface, due to flaws which may be invisible to the unaided eye.

J. G. Holmes