Cheryl Emery, age 10, of Omaha: Neb.., for her questions
Who were the first people to make glass?
The pharoahs of ancient Egypt wore beads of glass and thought they were as valuable as rubies and emeralds. They drank from glass goblets which to them were as valuable as gold. The ladies of Ur, an ancient city of Mesopotamia, wore necklaces of colored glass beads. All this was many thousands of years ago.
We cannot say who discovered the magic recipe for making glass or when the discovery was made. But glass objdcts have been unearthed in the tombs of Egypt and the ruins of Mesopotamia dating back more than 5,000 years. Some experts think that glass making was first discovered in Syria and that the Egyptians learned it from the Syrians. We think that the original discovery was made between 5,000 and 10,000 years ago and it may have been made by accident.
The ingredients for making glass are common minerals in the earth's crust. The basic ingredient is silica, the chief mineral in sand. Small amounts of soda and lime are also needed. When these ingredients are heated to more than 3,000 Fahrenheit degrees, they melt and fuse together. When the molten mixture cools, it is hard, brittle glass. If the ingredients are pure, the glass will be clear. Traces of certain impurities give it color and glass may be made in colors that rival the rainbow.
Our modern world is a glitter with countless glass objects and we tend to take the beautiful material for granted. Not so the people who first made glass. They had no electricity, no oil or gas with which to make their furnaces very hot. They made their glass in small clay pots over wood fires. This is one reason why their glass was so valuable to them.
Today, a glass factory may brew 20 pots of glass at one time, each pot containing one and a half tons of molten glass. In such a factory, it is no trouble to turn on the gas for the furnace. And a modern factory may have 50,000 recipes for making different kinds of glass.
The ancients knew nothing of these refinements. Most likely they made their colors by accident. A trace of iron in the silica. would make green glass, like emeralds. A trace of copper would make red glass.. like rubies. A certain Roman writer tells how some sailors discovered the recipe for making glass by accident. One night they rested on a beach in Palestine and built a campfire. The hearth stones they used were natron, a natural stone containing soda. The fire fused the soda with the silica and in the morning their were gobs of clear glass in the ashes. But this event happened thousands of years after the Egyptians were making glass.
Nature too makes glass by accident. A seething bolt of lightning may fuse the sand in a desert. The result is a long thin glass tube oalled a fulgurite or a piece of petrified lightning. Silica and other ingredients may be fused in a seething volcano. The result is a black glass rock called obsidian. This volcanic glass is plentiful in Yellowstone National Park where the Indians used to gather it to make hard, sharp edged arrowheads.