This section is from the "The New Student's Reference Work Volume 5: How And Why Stories" by Elinor Atkinson.
When you make taffy, you drop a spoonful of the boiling mixture into a glass of cold water to find out when it is just right to pull. Wouldn't it surprise you to learn that the glass itself was made in much the same way as you make taffy? First the materials are boiled together until the mixture is just right to pour into moulds, or to be stretched into bubbles or rolled into plates.
This seems strange of anything as hard and brittle as glass, doesn't it? But, in the great world of things that men make, it seems to be much as it is in the world that nature makes. There are only a few ways of doing things. The man who invented the spinning frame for making cotton yarn got the idea in an iron rolling mill. And there are only a few things to make everything out of. These are the elements of the earth, the air and water. So when we speak of men making things, we do not really mean what we say. All men can do is to take the things that are already made and combine them in new ways, or make new uses of them. Very, very often they merely find things that never were hidden.
Glass is one of the things that was found. No one knows just where or how it was found first. But very likely it was in Egypt, where the soil is mostly sand. You have noticed how sand shines, how it glares under the sun. Glass and glaze and glare all mean much the same thing. Now, in Egypt, straw stacks were often burned. In the ashes lumps of glass were found. If you were to find a lump of glass in ashes today, you would naturally think it a bottle that had been melted in the fire. But in old Egypt there were no bottles, no manufactured glass at all. The straw stacks of Egypt stood on sandy soil. Sand melted alone does not make glass, but when mixed with soda it does. There is soda, or potash, in ashes. The ashes of the straw, fused with the sand, very likely, and hardened into lumps of glass. And, besides, there is some glass, or silica, in straw itself, and in many other plants. Did you ever cut your hand on the sharp, glassy edge of a grass-blade? It is just possible that the straw itself furnished all the materials for the lumps of glass. All that was needed was a hot enough fire to melt them together.
The finding of glass where straw had been burned, set those wide-awake Egyptians to thinking and experimenting. They learned to mix sand with ashes, melt them together, and mould, roll and blow glass into various shapes when it was soft and hot. Our word "soda," is the name the early Italian glass makers gave to ashes. "Soda" really means solid. Today, by soda, we mean an alkali. But soda still has that old meaning of soldering or solidifying. It was the soda that fused the sand into a solid mass.
If one of your window panes could tell the story of its birth in a fiery furnace it would say something like this: "I have some of the same things in me as you have. Two of them are silica and lime. You have silica in your glossy (glassy) hair, and lime in your bones. Pure white sand is nearly all silica. And I was made with heat. You couldn't live unless you were made warm either. I needed more heat than you, that's all. You use sunshine. I used dead and gone sunshine—coal. As the plant is made up of little cells that the sun acts upon, so every grain of sand in me was acted upon by the fire.
"The heat made the little silica cells in the sand fly apart, and it separated all the other things that are in the sand from them. Then the silica particles flowed together again. ' Birds of a feather flock together,' you know. Iron particles flock together when the iron ore is melted. So do gold and silver and silica, or glass. The particles in the sand that are not glass go off by themselves. Where do you suppose they go?
"They just evaporate or disappear in gas. They are attacked by the soda. Soda, lye, potash, or some other alkali does something of the same sort to fats and oils in making soap. It breaks up the fat and eats particles that are not soap. Lime is the purifier, making impurities float to the top. You purify your house with lime. Heat helps, too, as it helps soda and sour milk make a gas to raise mama's biscuits in the oven."