from the Glass Encyclopedia
from the Glass Encyclopedia above: clear glass changed to purple If you are looking for Sun-turned Glass there is often some for sale on eBay. See what there is just now - click Sun-turned glass
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"Sun-Turned" or Irradiated Glass: A short explanation "Sun-Turned" glass is glass that has changed colour because of exposure to strong radiation. The same effect can often be achieved over a very long period by exposure to strong sunlight. Arsenic was used in glass-making before the second world war (pre 1940) and to a lesser extent after that date. When irradiated or exposed to sunlight for a long time, this glass turns yellow. The effect can be seen in the headlamps of very old cars. Manganese was widely used before about 1930 to decolorise impurities from clear pressed glass. Some glassworks went on using manganese after that time and some may still use it today. When irradiated or exposed to the sun for many years, antique glass with manganese turns purple. There are other chemicals which have been used in old glass which change the colour of the glass when exposed to strong sunlight or irradiation. Particularly vulnerable to these color changes are depression era glassware, sulphide marbles, Czech perfumes bottles, cut glass and early American pressed and blown glass. |
