The Essence of Glass
Essence of glass, glass making materials, production and processing of glass melt
The Essence of Glass
Glass is a solid solution of metal oxides in silicon oxide. As the glass cools down, the high viscosity of glass melt prevents the molecules from moving and thus also the crystallizing of siliceous compounds is disabled. The result is transparent glass. Its qualities – fusibility, thermal expansion, mechanical and chemical resistance, hardness, glance, light transmission and refraction – are determined by its chemical composition. Required properties are achieved by the appropriate combination of raw materials.
Glass Raw Materials
We distinguish three types of base raw materials, as per their function in the glass creation and qualities of glass - acidic materials having glass forming importance, alkaline materials – i.e. fluxing agents and stabilizers – and multi-compound materials such as shards and rocks improving the properties of the glass melt and facilitating the melting.
Fabrication and Processing of Glass Melt
The mixture of modified and weighed raw materials is transported into a gas furnace where, at a temperature of up to 1500 centigrades, it is melted to a thin glass melt. Such glass melt is refined. For the production of small quantities of glass, pot furnaces are used. Below a fireproof arc, several refractory pots are placed, surrounded by burning gas. The glass melt is taken for further processing using a blowpipe.
Once the viscous and plain glass melt cools down to the regular working temperature of around 1200 centigrades, glass products can be blown, cast, rolled, moulded or drawn into the form of panels, pipes and fibres. According to the product’s form we distinguish hollow (blown) glass, sheet glass and special glass (e.g. figurines formed using burner; pressed beading).
Hollow glass (bottles, glasses, beverage sets, light bulbs) is made by manual or automatic blowing. When using manual blowing, the glassblower scoops up fused glass melt onto the blowpipe (iron tube with a mouthpiece), and creates the initial bulb by a light blow. According to the desired size of the product, the glassblower adds more glass melt onto such initial bulb. Constantly rotating the blowpipe, the worker creates a semi-product and finally blows it into a wooden mould (watered) that gives the product its final shape. Separated from the blowpipe, the product is transferred into a cooling arch where it is continuously cooled down for several hours in order to balance the internal stress inside the glass.