Glass has been used by mankind for ages, but has been seen limitations in size and use due to its fragile and shatter-prone properties, which is why you didn’t see the Romans using frameless shower doors throughout their bathhouses.

In this two part series looking at the main types of safety glass, we’ll go into the process as to how each type is made and how it came about. For our first part we’ll be looking into tempered glass.

Tempered glass is believed to be first patented by Austrian chemist Rudolph A. Seiden in the early 20^th century. Simply put tempered glass is a type of safety glass in which the glass is thermally or chemically treated to strengthen  and alter the way it breaks apart. Once treated the now tempered glass is much stronger than normal glass and if it is broken it will no longer shatter in long, sharp sheets characteristic of normal, untreated glass. Instead, upon breaking it shatters into small fragments that are less likely to cause harm or serious injury as a broken sheet of glass.

In order to enter this tempered state, the glass can be treated in one of two ways: thermally (heat) or chemically. To thermally treat the glass, it is heated to around 1,200 degrees F, then quickly cooled to 500 degrees F. It’s this quick cooling that creates the tempered properties in the glass. Alternatively it can be chemically tempered through the “immersion of the glass into a bath of molten potassium nitrate.”

Unfortunately, because of the change in properties after the tempering process the glass cannot be cut or pressed into shaped as this will cause it to shatter, so this must all be done ahead of time. Also if it is scratched, it has been known to splinter and later shatter, to help prevent this from occurring, lamination of the surface can be used. The use of lamination will bring us into part 2: Laminated Safety Glass.