What's the Difference Between Tempered Window Glass and Standard Glass?

Posted: Jan 07, 2013
Author: Windows & Doors By Design

All window glass is made by mixing lime, soda, ash and sand together, then melting it at extremely high temperatures. The hot liquid is transformed into glass by drawing, pressing or blowing. Once glass has been formed, it goes through the annealing process where it’s reheated and cooled to change its properties.

The annealing process determines whether the end product will be standard window glass or tempered glass. Tempered glass is cooled down very rapidly, whereas standard glass cools down slowly. Tempered glass is also called strengthened or toughened glass because it can withstand at least 4 times the pressure of standard window glass.

The most notable property of tempered glass is how it breaks or shatters. Standard glass breaks into unevenly shaped, sharp, large shards. Tempered window glass shatters into evenly shaped, small pieces to reduce the risk of injury to anyone coming into contact with them.

Standard glass breaks in the exact area of contact, which results in holes or cracks in a specific location, with the remainder of the pane intact. With tempered glass, the panes are more resistant to impact, but they shatter completely with no areas intact. As such, tempered window glass is recommended for applications where safety is of paramount importance.

Although there does not appear to be any outward difference between the two, tempered glass is more scratch resistant and heat resistant than non-treated standard glass. Also, you can drill holes into standard glass, but toughened glass can’t be reworked at all once it has been tempered.