Glass is everywhere we look. From the bottles and jars on our shelves to the mirrors we look into and the windows we look out of. Glass is such a part of our lives that we take it for granted and few of us consider the fascinating history behind this product.
The very first glass was natural, a product of volcanic activity and even lightning strikes, heat being the driving factor in its formation. Obsidian is an example of natural glass and it is thought that our Stone Age ancestors used obsidian as a cutting tool. Pliny (23-79 AD), a Roman historian makes mention of Phoenician merchants ‘discovering’, by which he likely means finding, glass around 5000BC.
The first man-made glass is thought to have occurred in 3500BC in Mesopotamia, an area that today corresponds largely to Iraq and along the Tigris and Euphrates rivers. Clear glass beads have been found dating to this period.
Perhaps we need to define what constitutes man-made glass. Glass is made by melting together sand and minerals at high temperatures. Chemically, glass is more like a liquid and only at room temperature does it take on a more ‘solid’ appearance.
This liquidity is what allows glass to be poured, blown and molded. Silica (the sand component) combined with soda ash and limestone is the basic recipe for glass but other ‘ingredients’ are added to form different types of glass and to produce colored glass.
By 1500BC it seems that man had discovered the ability to make glass vases. Evidence for this was found in Egypt. The Pharaoh Thutmosis III has his name engraved on three such vases that survived to tell their tale today. Molten sand was poured over a central mould and turned to create the shape and the hollow centre.
It took another 500 years for the art of glass to spread via Alessandria to Italy and stone tablets dating to the rule of the Assyrian king, Ashurbanpial (669-626BC) are thought to be the first evidence of an instruction manual for the art of working in glass.
It is not exactly certain when glass-blowing was discovered but it is attributed to the Syrians in around 27BC. The method of blowing glass, via a thin tube, has changed very little since that time.
The Romans were the next to add to the history books. Via the spread of the Roman Empire, the technologies for working n glass were spread across many countries. Circa 100AD, Romans discovered clear glass by adding manganese oxide to the mix and glass thus found its way into architecture. The first glass windows were not of great quality, being somewhat opaque.
There was little development for many years, Alexandria and the Rhineland being the only noted examples of glassmaking skills and the Portland Vase is thought to be the best example dating from these times.
It wasn’t until the 11th century that the next major development occurred, that of sheet glass. Still using the blowing technique, German craftsman created hollow glass spheres which were sung vertically. Using the effects of gravity, this created cylindrical pods that, whilst still hot, were then cut at the top and bottom and laid flat to create sheets up to three meters long.
Italian glass, especially Venetian, dominated throughout the 15th and 16th centuries. In 1674, an English glassmaker by the name of George Ravenscroft applied for a patent for a new development, lead crystal. He had been asked to find a substitute for the Venetian crystal and by adding larger amounts of lead oxide to the potash and quartz mixture he created this new form of crystal.
In 1688, French glassworkers developed plate glass which was mainly used for mirrors. The term ‘plate’ came from the process of pouring the molten glass onto a special round table and the cooled glass was later ground down with rotating discs, fine sands and lastly, felt discs. This produced a much higher quality of glass mirror.
The late 18th and early 19th centuries saw the next shift in glass. The Industrial Revolution saw glass become a major industry. The main character in the development of modern day glass was a German scientist by the name of Otto Schott. Schott turned the eye of science on glass and his research led to developments in the reaction between chemicals and the thermal and optic properties of glass.
Around the same time, Friedrich Siemens invented the tank furnace which replaced the pot furnace and allowed greater amounts of glass to be melted at one time. The automatic blowing machine, invented by Michael Owens, an American engineer, arrived around the beginning of the 19th century. Between 1923 and1925, the gob and IS machines were invented that allowed glass bottles to be made by a single machine and is still the preferred method of production today.
Aside from some minor developments in the production of flat glass, allowing more consistency in thickness and larger sheets to be produced, little more has happened in the field of major change in glass but workers in the industry are still looking at ways to improve the glass that we take for granted every day.