Description

Glass materials have a random, liquid-like (non-crystalline) molecular structure. They are excellent thermal insulators and electrical insulators, and have high dielectric strength. At ordinary temperatures, glass materials are relatively strong, inert, biologically inactive, and corrosion resistant.  

How Glass Materials are Made

Glass materials are heated to a temperature sufficient to produce a completely fused melt.  During fabrication, the properties of glass can be greatly modified by additives or heat treatment. Examples of raw materials include cullet (crushed, recycled glass), sand, soda ash, limestone, and additives.

Types

GlobalSpec provides product information about these and other types of glass materials.   

• Embedded glass has embedded wire for resistance heating or reinforcement.
• Tempered glass provides increased strength and can shatter into small pieces when broken.
• Borosilicate glass offers superior durability, chemical, and heat resistance, which make it suitable for use in chemical processes, in the pharmaceutical industry, in high-powered lamps, for cookware and other heat-resistant products.
• Soda lime glass is used in everyday products such as bottles, jars, drinking glasses, and window glass.
• Lead glass (also called lead-alkali glass) has a high percentage of lead oxide (at least 20%) to increase its index of refraction. It is relatively soft, a better electrical insulator than soda-lime or borosilicate glass, and used for optical applications such as prisms and lenses.
• Electronic glass is used in fabricating electronic components such as X-ray tubes, display devices, and chip components.
• Opal glass is used to diffuse light uniformly.
• Fused silica glass has excellent resistance to thermal shock, withstands high operating temperatures (1,200° C for short periods), and is used in optical waveguides and crucibles for growing crystals.

Standards

ASTM International (formerly called the American Society for Testing and Materials (ASTM) Technical Committee C14 on Glass and Glass Products maintains several standards for glass materials. These include ASTM E708-79(1999) Standard Specification for Waste Glass as a Raw Material for the Manufacture of Glass Containers.

The International Organization for Standardization (ISO) supports Technical Committees on glass materials, including TC 48 on quality of glassware and TC 160 on glass in building.