Sunday, July 10, 2011

Why Glass Comes in Different Colors

From Earth 911

Why Glass Comes in Different Colors

Crushed glass, or cullet, is melted down to form new glass containers. (Stock Photo)
Glass is renewable and one of the only materials that can be endlessly recycled without losing strength or quality, so the glass found in your spaghetti sauce jar or wine bottle can go from the recycling bin to store shelves in as little as 30 days.

Color Significance

Have you ever wondered why beer usually comes in amber glass and wine is often in green glass?

Brown glass absorbs the most ultraviolet radiation, at wavelengths shorter than 450 nm (nanometers), so it offers the best protection from potentially damaging light. Beer, for instance, would be ruined by light absorption so you’ll usually find your favorite brew in a brown bottle.

Green glass still has the light protection, but not as much and since liquids like wines and juices can be exposed to some light without ruining the flavors, they are often bottled in green glass.

Clear glass is best suited for alcohol, water, sauces and foods that aren’t affected by light.
All of these glasses are colored by the addition of oxides colorants to the forehearth, a brick lined canal that delivers glass to the forming machine of a flint glass furnace, during the manufacturing process.

Iron, sulfur and carbon are added to make amber glass. Chrome oxide is used to create green glass; the higher the concentration, the darker green the glass will be. Blue glass, which was more popular in the 1920s, is created by adding cobalt oxide

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