What would life be like without glass? A lot of modern technology—like computers, cameras, and smart phones—depend on it. Decorative or utilitarian, it’s all around us, often right in front of us, and we are accustomed to looking straight through it.
Humans have been using glass since prehistoric times. Obsidian, a type of volcanic glass formed by rapid cooling of viscous lava, has extremely sharp edges, making it ideal for arrowheads, knife blades, and other cutting implements. Before the discovery of a recipe for manmade glass, ancient humans used obsidian to make weapons, tools, and ornaments.
Basic glass production has not changed much since ancient times. A mixture of silica, soda ash, and lime is heated to extreme temperatures, shaped into almost any form, and then allowed to cool. There is evidence of glassmaking as early as 3500 BCE in Mesopotamia. Beads, likely an accidental byproduct of metalworking, are the earliest known manmade glass objects. A surge in glassmaking technology during the late Bronze Age in Egypt and Western Asia produced decorative vessels of patterned and colored glass. The archaeological record indicates that the method for making glass from raw materials was a closely guarded secret in powerful nations. Outside of the wealthy empires, glass workers had to acquire bars of pre-formed glass to produce wares.
An early glassmaking technique was core forming. Glassmakers wound lengths of hot glass around a core of ceramic-like material to shape the body of the vessel, then added handles and a rim. When the vessel cooled, the core would be removed. Pouring hot glass into a mold is called casting. After the cast glass cooled, grinding and cutting techniques were used to refine and decorate the piece.
Pouring molten glass into molds was a slow and unreliable method that kept glass a luxury item for the wealthy. This changed in the 1st century BCE when Syrian and Palestinian workers discovered the art of glass blowing, inflating a glob of molten glass into a bubble at the end of a tube. The glassblower could manipulate the pliable glass into virtually any shape while adding artistic flourishes. The new manufacturing technique transformed glass into a cheap and easily produced material, gradually replacing clay and metal vessels.
James Mongrain’s amazing interpretation of mid 18th century Venetian goblets.
Modern technology has improved glassmaking with the introduction of additives which provide color or opacity, improve quality, durability and other properties. One relatively recent innovation is the “float glass” process, first introduced in 1957 in Great Britain by Sir Alistair Pilkington. Before this method was perfected, it was impossible to create flat sheets of smooth glass with uniform thickness. Screens for laptops, mobile phones, digital cameras, and camcorders are made from float glass.