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K2O acts like Na2O, which extends the frit and enhances the gloss and transparency of the glass. When the colored glass is melted, the coloration is more vivid. The K2O in the glass is usually introduced by a potassium base (K2CO3) having a specific gravity of 2.29, which often contains a small amount of impurities such as Na2CO3, K2SO4, KCl or the like. Potassium is easily absorbed by water and deliquesces and must be placed in a dry and ventilated warehouse. Because the price of potash is higher than that of soda ash, it is only used in optical glass and lead-potassium glass. The amount of pot glass is very small, generally below 3%.