Heat strengthened glass is similar to tempered glass except that after heating the glass in a furnace as in the case of tempered glass, the cooling is done at a much slower pace. The heating temperature remains nearly the same for both processes. The residual stress on the edge and the glass surface differ in both cases with tempered glass having a higher level of stress.


Due to the relatively lower rate of cooling during the strengthening process, heat strengthened glass develops less stress as compared to fully tempered glass.