material world: clear glass

Transparent or sandblasted, mouth-blown or machine-made, borisilicate or soda…glass. It can take on almost any form imaginable—from purely functional window panes and high performance lab glass to art glass and brilliant crystal chandeliers—the basics don’t do justice to this most versatile material.

Most likely an accidental creation of residue chemicals in an oven, pieces have been discovered in Mesopotamia from 3000BC and Egypt from the late Bronze Age…so much for its delicate nature.

While most transparent glass has a slight green or blue tint—which is caused by iron that acts as a lubricant in the manufacturing process—‘crystal clear’ lead glass is made with lead oxides, instead of calcium, and is usually used for cut stemware or sparkling crystal jewelry. And even though glass has no crystalline structure chemically, the term stuck like qwerty keyboards. Early window panes, photo courtesy of: lady_lbrty

Generally speaking, most commercial glass made today is soda glass—a mix of sodium carbonate from soda ash, calcium oxides from limestone, magnesium and aluminum oxides. Heated to temperatures over 2000°F, glass begins as a thick liquid—with a high viscosity—and takes shape as it cools. Shapes can be made by literally mouth-blowing the glass through a long pipe or by machines and molds. Blown glass can be thick or thin and fine, like lumi candleholders, while machine made glass is usually thicker like bari bowls.

As further testament to its durability, glass has been battling the elements of nature as an architectural material for hundreds of years. Stained glass windows brought drama to Medieval stone cathedrals, and early window panes were actually mouth-blown into a flat shape which can be easily identified by their wavy surface and circular centers. In more recent centuries, and in its simplest ‘float glass’ form, they’re the key element of modern structures—from high-rise skyscrapers to International Style homes.

Farnsworth House, photo courtesy of: tinyfroglet