Glass fusion and furnace refractoriesThe age-old art of making glass has now become advanced science, but it remains as fascinating as ever, demanding special knowledge and skills in chemistry, materials science and refractories. The properties, quality and price of glass are governed by the choice of raw materials and the fusion chemistry of the melt (i.e. the molten mixture of raw materials). |  |
The colour of the glass and in particular its absorption of light at certain wavelengths are controlled by the judicious choice of coloring agents (covalent metals, colloids etc.) and the reducing/oxidising (redox) state of the glass. This permits different colours to be obtained with varying degrees of intensity. Meanwhile, the specific absorption controls the selectivity of the glass (i.e. the ratio of light transmission to energy transmission). The latter is very important to keep out the heat of the sun and yet maximise natural light inside buildings and vehicles.
It gets even more complex: the properties of the glass are also influenced by interactions between the melt, the furnace refractories and atmosphere, and the tin of the float tank and its reducing atmosphere. Finally, the characteristics of the raw materials and the interaction between the melt and the furnace atmosphere lead to corrosion and wear of the refractories, which also has to be taken into account.
The rheological properties (relation between the temperature of the glass and its viscosity) are mainly governed by the chemical composition. By controlling the chemistry of the glass its properties can be adapted to make it suitable for further thermal treatments, such as bending or tempering, for example to obtain a high quality car windshield. The various techniques used include crucible melt tests, chemical and cristallographic analysis and float simulation tests.
The areas of expertise required in this field are:
- Chemistry
- Geology
- Mineralogy
- Crystallography
- Materials science
- Knowledge of refractory materials
- Corrosion