History of Tempered Glass

Tempered glass is a type of safety glass used in buildings and automobiles to decrease risk of injury if the glass breaks. It has been in use since about 1940, with greatly increased demand in the past 50 years. The need for safer glass and the development of building and automobile safety regulations has driven the demand for tempered glass manufacturing.

Origins

Tempered glass was developed in the early 1900s, though no specific date is known. The first patent is said to be held by Rudolf Seiden, an Austrian chemist who emigrated to the United States in 1935. Pittsburgh Plate Glass Co. developed Herculite tempered glass in 1938 but stopped producing it within a few years as the company focused on regular float glass.

Types

There are two processes that are used to make tempered glass. For vertical tempering, the glass is held in a vertical position by metal tongs and moved through the furnace. Tong marks are left on the edge and usually cannot be seen if the glass is installed in a frame. Horizontal tempering moves the glass through the furnace on rollers in a horizontal position. This can leave a slight wave caused by the rollers, but it is usually not visible to a casual observer. Horizontal furnaces are the more common method of tempering glass in use today.

Regulations

Safety regulations for glass started in the 1960s in response to a rising number of injuries caused by broken glass in buildings and automobiles. These regulations greatly increased the demand for tempered glass, causing an increase in the number of glass companies in the 1970s and 1980s.

ANSI Standards

The Accredited Standards Committee, working under the auspices of the American National Standards Institute, developed the American National Standard for Safety Glazing Materials Used in Buildings in 1966. The current version is ANSI Z97.1-2004. According to the "Glass Informational Bulletin," ANSI Z97.1 is a voluntary safety performance specification and test method.

CPSC Standard

The U.S. Consumer Products Safety Commission adopted the Safety Standard for Architectural Glazing Materials in 1977, known as CPSC 16 CFR 1201. It was last amended in 1982. The CPSC is a federal standard that mandates when and where safety glass must be used.

Federal Specification DD-G-1403B

Federal Specification DD-G-1403B was developed by the General Services Administration in 1972 and modified in 1983 to regulate the use of heat-strengthened and tempered glass in building construction. This specifies the strength requirements that must be met to qualify as heat-strengthened or tempered glass.