A Little History

• Glass has been around almost since the discovery of fire. Theoretically, with enough heat, you could take the dirt under your feet and make glass. The most popular ingredients are sand (silica), soda ash (common ingredient of soap) and limestone, which are heated and combined to form a transparent stable substance. It can be shaped in many ways such as casting, rolling and blowing to make what we call glass.
  
  

A big secret

• Each manufacturer has its own secret recipe, but they cannot change the laws of chemistry--glass retains the molecular structure of a liquid. If you use a precision measuring tool on a pane of glass that has remained vertical for a very long time, it will be thicker at the bottom than the top. This is also the secret to cutting glass without a saw or knife. The wheel on the glass cutter lines up the molecules for a short period of time, allowing the technician to break the glass on the mark.
  
  

The Color of Clear

• Because the basic ingredient in glass is sand, which contains iron, it has a tendency to turn green when exposed to light. The thicker the glass, the more pronounced the color is at the edge. Varying additives have been used to stabilize the color throughout time, each having a different effect. Until about 1915, manganese was the element of choice. When the manganese is exposed to the ultraviolet radiation from the sun, it oxidizes and gives the glass a purple tinge.