Glass is made of naturally from a fusions of silica (sand), soda and lime. This fusion can be achieved merely by lightning striking in a place where the right ingredients happen to be adjacent to each other. When glass is made by man, other ingredients are added, such as potash, lead oxide and boric oxide. Some of these ingredients are used to make glass clear, some to color it, and others to give it a frosted effect.
Glass was made by potters in Egypt for glazing stone beads as early as 12,000 B.C. As Egyptian culture progressed, craftsmen used glass for the manufacture of personal ornaments and bottles.
A tremendous step forward in the use of glass was made by the Phoenicians in about 300 to 200 B.C. by the invention of the blowpipe. The blowpipe is a hollow iron tube with a mouthpiece at one end and a knob shape at the other. The knob-shaped end is dipped into hot, viscous glass. A “gather” of molten glass remains on the end when the pipe is withdrawn. This hot glass can be blown by the worker into a hollow ball. The harder he blows, the larger the ball.
During the Roman civilization the art of glass-making reached near-perfection. In the 3rd Century, the Romans cast glass on flat stones and produced the first window panes. The break-up of the Roman Empire and the ensuring Dark Ages brought an end to such cultural developments. The glazing of windows did not become widespread over the whole of Europe until the 15th and 16th Centuries.