The manifold forms and uses of glass are becoming increasing­ ly important in science, industry, and our personal lives. This constantly improving material interests a range of people extending beyond the relatively small number of glass experts. Naturally, questions arise as a result of this widespread interest. For this reason, we have heeded the publisher's suggestion to develop a glass primer which answers many questions and explains much of the terminology. The bases for this Schott Guide to Glass were the lecture manuscript, 'Glass Science for Designers' by Prof. Dr.-Ing. Heinz Pfaender, and the Schott pamphlet, Concepts of Technical Glass from A to Z. The manuscript which evolved into this book was written by members of the Schott scientific staff. We thank all those involved in producing this reference work. The Schott Guide to Glass will give experts, interested amateurs, and those who work with glass a glimpse into the diversity of this fascinating material. Mainz, Germany, September 1995 The editor Schott Glaswerke Introduction Glass is possibly the oldest man-made material, used without interruption since the beginning of recorded history. Unlike bronze or iron, however, it has not lent its name to any historical epoch. Still, the use of glass from hand-blown goblets to electronic components has grown with the rise of the industrial era and greatly affects present life. Glassmaking has always been one of the few truly integrated manufacturing processes where native minerals are transformed into an incredible variety of finished products within a single factory.