The Compositional Analysis of Glass

Glass just fascinates me, but I've never really thought about why, so when it was time to update my history of glass making, I decided to use appropriate photographs where I could find them. In the process of assembling the new Illustrated History of Glass-Making, I discovered that over the last few years, a lot of research has been conducted on the chemical makeup of different glasses.

Blown Glass Bottle from Sidon (Lebanon), ca AD 150-250
Photo Credit: Marie-Lan Nguyen

In general, glass is made by combining quartz sand with a variety of different additives, and the combination is then exposed to heat and molded or blown into vessels and table ware and art objects. Manufactured glass is actually pretty old--glass-based glazes on pottery date to the mid-fourth millennium BC and glass objects were first made about 1500 BC. The different recipes for making glass changed over the long centuries, including a true alchemist's blend of natron and salts and metals, to produce clarity or colors or transparency or opacity. Almost all of the original glass recipes are lost to us today, although a very few were recorded in old records like Mesopotamia's Library of King Assurbanipal.

Over the last few years, compositional analysis of old glasses has been conducted on a wide range of materials from the centuries of production. These analyses reveal the chemical makeup of the glasses--basically, reverse-engineering of long-lost glass recipes. This corpus of data has grown to the point that glass researchers can now compare and contrast recipes and track historical paths that haven't been available to us.

My Illustrated History of Glass is based on several studies of those recent compositional analyses. The history begins with the Middle Paleolithic use of natural glass and (at the moment) ends in Venice in the 7th century AD. Look for lots of side trips to some of the workshops throughout history. Recipes aren't included, but for those interested in further investigating this fascinating alchemy, I've assembled a bibliography for this project.

• An Illustrated History of Glass Making
• Bibliography of Glass Making