Chapter 1 - Introduction

Abstract

The word glass is derived from a late-Latin term glæsum to mean a lustrous and transparent material. Glassy substances are also called vitreous, originating from Latin word vitrum (clear). The history of glass as glazed stone beads goes back perhaps as much as 12,000 years. As independent objects, glassware was available ~5000 years ago. The most important technological developments in glass, perhaps as the glass window, were sponsored by the Christian Church during the Middle Ages on the European continent. Although transparency, luster, and durability against elements of nature are neither sufficient nor necessary to describe glass, they remain some of the key characteristics of glass that are important to large-scale commercialization. More than 95% of the commercial tonnage is oxide glasses, of which the vast majority is silica based. Vitreous silica, soda lime silicate, borosilicate, lead silicate, aluminosilicate, and optical glasses are the primary glass families. Of the nonoxide glasses, those of significant commercial interest are the heavy metal fluoride glasses (HMFG), the amorphous semiconductor and chalcogenide group, and glassy metals. Of these, the amorphous semiconductors and the chalcogenides form the basis of miniaturization of the computer as switching and memory devices, solar cell (photovoltaics), and the xerographic process (photoconductivity). Glass is also found in nature. The more important and interesting examples are volcanic glass (obsidians), lunar glass, and tektites (generally thought to be fused ejecta from a meteorite impact).