The chemical quality of glass is what makes up its color. Impurities in glass such as iron can give it a green or brown color. Adding chemicals to the glass can give it different color intensities and effects. For example, adding copper to glass can make it blue, while adding tin can make it white.
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BARBARA KLEIN: It is hard to say exactly when humans first started making glass. The Roman historian Pliny said that Phoenician sailors accidentally discovered how to make glass over three thousand years ago. The sailors landed on a beach and started a cooking fire near some containers of the mineral natron. The next day, they realized that the sand and natron under the fire had melted then cooled into glass. Other experts say glass making first started four to five thousand years ago in ancient Mesopotamia, present day Iraq and Syria.
STEVE EMBER: One of the earliest methods developed for making glass containers is called core-forming. A glassmaker places a rounded piece of clay material on the end of a long metal stick. Once the clay dries, the glassmaker dips the form in a container of hot liquid glass until it is covered. The artist can then add a second color of glass to make designs over the first layer of glass. Once the glass form cools completely, it is taken off the metal stick. The clay inside is carefully cut out to form a glass container.
BARBARA KLEIN: Another ancient method of making glass that is still used today is called casting. Casting involves making a clay form in which the shape of the glass container is carved. Then, the artist puts small pieces of glass material inside of the clay form. When it is cooked at a very high temperature, the glass pieces melt and take the shape of the clay form. Once the solid glass object cools, an artist uses special tools to carve an opening in the container.
最新
2013-11-25
2013-11-25
2013-11-25
2013-11-25
2013-11-25
2013-11-25