Types of glass and market application
Lead glass is composed of 54-65% SiO2, 18-38% lead oxide (PbO), 13-15% soda (Na2O) or potash (K2), and various other oxides. When the content of PbO is less than 18% is known as crystal glass.
– In moderate amounts lead increases durability;
– In high amounts it lowers the melting point and decreases the hardness giving a soft surface;
– In addition it has a high refractive index giving high brilliance glass.
These two last properties make it appropriate for decorating purposes.
Glass with high lead oxide contents (i.e. 65%) may be used as radiation shielding glass because lead absorb gamma rays and other forms of harmful radiation, for example, for nuclear industry.
As with soda-lime glass and back painted glass, lead glass will not withstand high temperatures or sudden changes in temperature.
Borosilicate glass is mainly composed of silica (70-80%), boric oxide B2O3 (7-13%) and smaller amounts of the alkalis (sodium and potassium oxides) such as 4-8% of Na2O and K2O, and 2-7% aluminum oxide (Al2O3).
Boron gives greater resistance to thermal changes and chemical corrosion.
It is suitable for industrial chemical process plants, in laboratories, in the pharmaceutical industry, in bulbs for high-powered lamps, etc. Borosilicate glass is also used in the home for cooking plates and other heat-resistant products. It is used for domestic kitchens and chemistry laboratories, this is because it has greater resistance to thermal shock and allows for greater accuracy in laboratory measurements when heating and cooling experiments.