Glass is a versatile material designed to meet all sort of requirements. Be it our windows or the glasses we use to drink beverages; glass is used for several applications in our daily lives.
There are several types of glass differentiated based on their chemical, physical and optical properties. These differences in properties are due to the variations in the ingredients and method of manufacturing.
Here are some of the most common types of glass and what they are used for.
1) Borosilicate Glass (SiO2, B2O3)
Borosilicate glass is made by mixing silica and boron trioxide with small amounts of aluminium oxide and alkalis such as sodium and potassium oxide. Nearly 70 to 80% of silica and 7 to 13% boric oxide is used to make this type of glass.
It is known for its superior chemical durability and thermal shock resistance. Due to its lessened susceptibility to thermal stress, it is commonly used in ovenware and lab equipment (reagent bottles). It is sold under many trade names such as Borosil, Pyrex, and Borcam.
2) Soda-Lime-Silica Glass (SiO2, Na2O, CaO)
Soda-lime-silica glass is the most common variety of glass, used for commercial purposes. Ranging from jars to window panes, about 90% of the manufactured glass is soda-lime-silica glass. It is made by melting soda (sodium carbonate), dolomite, lime, silica (silicon dioxide), alumina (aluminium oxide) and small amounts of fining agents such as sodium chloride, sodium sulfate, etc., at a temperature of 1675°C in a glass surface.
This type of glass is broadly divided into two categories, flat glass and container glass. Flat glass is used for windows, prepared by a float process and has a higher sodium oxide and magnesium oxide content. Container glass is used for containers, prepared by glass blowing process and has a lower sodium oxide and magnesium oxide (highly water soluble ions) content, thus making it ideal for storing food and beverages.
3) Phosphate Glass (P2O5)
Phosphate glass is made of the metaphosphates of several metals. Phosphorus pentoxide is the glass forming substrate in this glass as silicon dioxide was in the soda-lime-silica glass and boron trioxide was in the borosilicate glass.
This glass falls under the category of optical glasses. It is highly resistant to hydrofluoric acid and can work as an excellent heat absorber when mixed with iron oxide. But, it offers low resistance to chemical corrosion. It is mainly used in microscopes, scientific instruments, etc.
4) Lead Glass (PbO)
Lead glass is one of the most popular types of glasses due to its decorative properties. It was discovered by Englishman George Ravenscroft in 1674. Popularly known as crystal, this glass is made from lead oxide (18 to 40%). The heavy lead content enables it with attractive optical properties, raises its refractive index and lowers its viscosity.
This glass can be easily manipulated and is mostly used in various decorative objects such as glasses, decanters, etc. It is also used in radiation shielding as it absorbs gamma radiation and X-rays due to high lead oxide content.
There are different types of glasses manufactured for different uses. Their ingredients, process, melting point and properties differ from each other. Have a look around your house and see how many types of glasses you find.