Glass

In the movie Sweet Home Alabama, lightning strikes sand on a beach and forms an exotic glass sculpture. This is one of the ways glass can be formed in nature. The lightning is more than hot enough (20,000 C) to melt the silica in the sand. The resulting creations are called fulgurites (right), and, unfortunately for Hollywood, aren't quite the exotic, clear sculptures shown in the movie.

Man-made glass has been around for thousands of years. The oldest known examples are Egyptian glass beads from around 12,000 BC.

fulgerites

Glass is made from silica (found in sand) mixed with chemicals (typically soda ash or limestone) and heated to high temperatures (up to 2800 degrees C). Once it is melted, it can be treated many different ways: poured into molds, blown, pressed - as determined by the final product.

Glass can be melted down and made into new glass an infinite number of times. Using recycled glass reduces the temperature needed to create the new glass, and most industrial glass makers are set up to use significant amounts of cullet (recycled glass). Increasing the use of cullet in a furnace by 10 per cent results in an energy saving of approximately 3 percent, and for every tonne of cullet used, there is a savings of 1.2 tonnes of raw materials.

Because the raw materials (mainly sand) for glass are plentiful and cheap, cullet prices have remained steady and low (hovering around $40/tonne for clear glass) for many years. The price for coloured glass is even lower as most glass bottle makers won't accept coloured glass.

Saskatchewan has one main glass recycler, Potters Industries in Moose Jaw. They grind clear glass into very fine beads, which can be used to add to high-way paint to make it reflective.

The amount of glass in municipal waste streams is decreasing. While 15-20 years ago, glass was typically 6-7% of the waste stream, now it is less than 3%.

Many of the products that used to be packaged in glass have been switched to plastic (when was the last time you saw a glass coke bottle?). Also, as beverage systems moved away from reuse, the glass bottle has became thinner, since it needs to make it through only one use. Glass is still popular for beer, wine, and liquor bottles.

(Source: WasteWatch, March 2003)