Most of us have certainly never thought about who invented his window glass. It is just there and from time to time we have to clean it. But glass is much more fascinating than you might think. So what is it all about, with this strangely durable but completely transparent material that protects us from the cold and still lets the light in? Who first came up with the idea of producing this?
Glass was invented long before the Romans, but was almost forgotten in Central Europe afterwards. There were shortages in the supply of basic materials and after having possessed glass, people were again sitting with carpets in front of their windows in the dark fortress room of the Middle Ages. These dark rooms are so present to us Central Europeans that some believe that glass was only invented in the 12th century. In fact, the invention of glass is much older.
First of all – what is glass? Glass is (and I know that most people will be astonished to hear that) an undercooled liquid. When it is heated, it becomes liquid again. Glass, from Germanic glasa, “the shining, shimmering”, is not an exactly identified material, but a collective term of certain cooled, but not crystallized substances. Most glasses consist mainly of silicon dioxide, such as drinking glasses or window glasses. However, there are also natural glasses such as obsidian and amber.
Glass, especially obsidian of volcanic origin, has been used by many Stone Age societies to produce cutting tools. In the fifth millennium before Christ, glass was used for enameling for the first time. The first real glass objects, pearls, are known from Egypt and are dated to the third millennium BC.
Syrian and Egyptian glass was made with soda, i.e. sodium carbonate, which can be extracted from the ashes of plants, especially coastal plants such as the saltwort. The early glass production still looked quite different from what comes to mind today and what will mostly be the image of a glassblower. It was based on grinding techniques borrowed from stone processing. The glass was ground or carved in a cold state.
The techniques required for the first fusion of glass from raw materials were a strictly guarded secret. Areas that did not have the secret were therefore dependent on the import of preformed glass, often in the form of cast blocks found on the wreck of Ulu Burun off the coast of modern Turkey.
However, instructions for the production of glass can be found, for example, in cuneiform tablets discovered in the library of the Assyrian king Ashurbanipal (668 – c. 627 BC). During the Hellenistic period, many new glass making techniques were invented and larger objects were made for the first time.
In the 1st century BC glass blowing was discovered on the Syrian-Jewish coast and glass vessels suddenly became cheap. Glass containers made in Alexandria then spread throughout the entire Roman Empire and we still find them in archaeological sites. With the discovery of clear glass through the introduction of manganese dioxide, the Romans began to use glass for windows. Cast glass windows, though still with poor optical properties, appeared in Rome’s most important buildings and the most luxurious villas of Herculaneum and Pompeii.
After the collapse of the Western Roman Empire around 450 A.D., however, glassmaking declined rapidly and mostly only old glass was melted down again. When the Carolingian Empire expanded in northwestern Europe around 800 AD, the demand for glass increased, but the supply of traditional raw materials was difficult. Therefore, people experimented with new raw materials and began to produce ‘forest glass’. A strange, shimmering dark green glass.
It is a medieval glass, which was produced in northwestern and central Europe from about 1000-1700 A.D. from wood ash and sand and was produced in factories located in forest areas. Its composition is different from that of Roman glass. Its main problem was that it required enormous amounts of wood to produce potash (the potassium salt of carbonic acid). Potash was obtained by evaporation of suitable plant ash, mainly beech or oak.
Due to the manufacturing difficulties, glazed windows were a great luxury well into the Middle Ages and only became common again in the 16th century. The use of glass drinking vessels was similarly seen – glass was regarded as extremely precious and was only found in the households of aristocrats or the rich citizens of the city.
So let us be satisfied when we look out of our perfectly clean, transparent window tonight and drink a glass of wine. It could also be a leather cloth and a cup of wood. ���