Before discussing the environmental aspects, we give a brief description of the flat glass production process, as this is the process with the most environmental impact.
The basic raw materials used in flat glass production are:
- Glass-forming materials: silica sand and glass cullet.
- Intermediate and modifying materials such as sodium carbonate, dolomite, limestone, sodium sulphate, feldspar and blast furnace slag.
- Colouring and coating agents such as iron oxide and other metallic compounds.
The basic principle of the float glass process is to mix the raw materials, melt them in the furnace and pour the molten glass onto a bath of molten tin. The combustion in the furnace uses air and gas/fuel oil. The glass solidifies as it floats on the tin bath. After the tin bath, the glass ribbon passes on to an annealing zone where it cools down gradually while being carried on rollers. Sometimes coatings can be applied on the glass just after leaving the tin bath. At the end of the annealing zone the glass is cut into sheets. Depending on the situation, the glass can be processed into other products.
- Glass for mirrors can be painted and silvered
- Glass for architectural purposes (buildings, furniture etc.) can be coated, made into double glazing units, tempered, painted, laminated, etched, etc.
- Glass for automotive can be enamelled, curved, tempered, laminated, etc.