How do you know if tempered glass has the proper surface compression (greater than 10,000 psi according to ASTM C1048)?
The glass fabricator can use an instrument to measure surface compression. The Grazing Angle Surface Polarimeter (GASP) is an instrument used to measure surface stress in the glass. Another test instrument is called a DSR (differential surface refractomer). Alternately, the glass fabricator can break the glass and examine the fragments to see that they meet the criteria in ANSI Z97.1 or CPSC 16 CFR 1201. If the glass does not break after the shot bag impact, it can be broken with a center punch.
