David Hall, Age 12, of Victoria, B  C  ,

What do they use to make glass?

Our modern chemists have given us a host of new plastics to do countless Jobsand pretty up our everyday world  But one of the first of the plastics, and still the most beautiful, is glass  The ancient Egyptians were making glass beads thousands of years ago  At that time, colored glass was more valuable than rubies and emeralds  Through the ages, we have improved the skills of glass‑making, and developed thousands of different recipes for making glass for different purposes  Certain optical glass is actually as flawless as gem stones  Certain decorative glass rates among our precious works of art 

The basic recipe for glass‑making, however, is as simple as it was in the beginning  The raw materials are plentiful minerals in the earths a crust, and therefore cheap  Moat of the cost of glass arises from the labor entailed and the expensive furnaces, for the raw materials must be fused together under temperatures of thousands of degrees  Then too, there is special packing and shipping, for everyday glass is brittle and fragile  In this respect a drinking glass cannot compete with a plastic one which can bounce without breaking 

The basic ingredient for glass‑making is the mineral silica which is also the basic ingredient of sand  The best sand to use is snowy white arid net too fine  It should be about 99 per cent silica and, if there are traces of iron in the mineral, the finished glass will be green instead of clear  Most of our sand or sandstone for glass  ‑making comes from deposits in New Jersey, Pennsylvania, West Virginia, Illinois and Mi s sour I 

Glass can be made by melting silica alone, but this requires a very,, vary high temperature  When an alkali is added, the silica melts and fuses with lees heat  The alkali mineral used may be potash, which is potassium carbonate  It may be soda ash, which is sodium carbonate  The glass made from silica and a soda alkali alone is water glass ‑ it dissolves in water: A third  ingredient is therefore added as a stabilizer to make the finished glass  firm and darable  The stabilizer most commonly used is lime which comes from the plentiful deposits of limestone in the earth is crust  Other stabilizers used in the making of special types of glass may be zinc,  magnesium, aluminum or compounds of boron 

Small traces of other ingredients may be added to remove impurities from the mixture or to add sparkling tints of dye‑catching color  For making everyday glass, the mixture is heated to around 3,000 Fahrenheit degrees  Special types of glass may be heated and reheated to even  higher temperatures  In the furnace the silica, the alkali and lime fuse together to form the bright, solid, hard and transparent plastic which is glass