Welcome to the Glass Age

27 T 2. Glass History and the Arrival of the Glass Age J ohn C. M auro and J ohn M. P arker his chapter explores the history of glassmaking and its role in advancing civilization throughout recorded history, highlighting the enormous contribution glass has made to human society over millennia and how it still plays a vital role, perhaps more than ever. It builds on the arguments in Chapter 1 that we now live in the ‘Glass Age’ and many themes introduced here are expanded in later chapters. Typically, glass is a material we look through, so its importance is often unseen and unnoticed; this book aims to redress that imbalance. Glass compositions Using the term ‘glass’ is a little like calling a steel girder, a copper wire, an aluminum can or a brass doorknob simply ‘metal’. Glassy products have many compositions and fabrication routes according to their end use. Mostly, glasses are made by melting appropriate raw materials, then shaping and cooling back to room temperature without crystallization. The composition and chemistry define what wavelengths of light are transmitted; the melting process is designed to create a bubble- and crystal-free homogeneous product with no internal boundaries where a refractive index step would scatter light and destroy transparency. Consider for a moment how effectively finely ground icing sugar hides the imperfections of the cake underneath because of those boundaries between the many small but individually transparent sugar grains. Most common glasses have silica (sand) as a significant component and this chapter begins with silica-based