Glassmaking in the Old Days

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Egyptian glassmakers melted glass in open fireplaces in clay bowls. Burnt pieces were thrown incandescent into the water, where they cracked. These fragments, the so-called frits, were ground by the millstones to dust and melted again.

Glass. The second half of the 4th century.
Glass. The second half of the 4th century.
The medieval melting furnace (“goot”) was a low, wood-burning vault, where glass melted in clay pots. Laid out only of stones and alumina, it could not stand for a long time, but the supply of firewood was not enough for a long time. Therefore, when the forest around the goot was cut down, it was transferred to a new place, where the forest was still in abundance.


Another furnace, usually connected to the smelter, was an annealing furnace - for quenching, where the finished product was heated almost to the glass softening point, and then quickly cooled to compensate for the stresses in the glass (to prevent crystallization).

In this form, the glass melting furnace lasted until the end of the XVII century. The shortage of firewood, especially in England, forced in the XVII century to convert some goots to coal. Sulfur dioxide volatilized from coal and stained glass yellow, so the British began to melt glass in closed, covered pots. This melting process was difficult and slowed down, it was necessary to prepare the charge not so solid. Nevertheless, already at the end of the XVIII century, the use of coal becomes predominant.
Modern Colored Glass
Modern Colored Glass

It is curious that during its existence, unlike many other materials, glass, as a substance and material of mineral origin, has not undergone almost any changes. The earliest examples of what became to be called glass are no different from, for example, the well-known bottle. The exception, of course, are the types of glass with the given properties.

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