Ordinary window glass, oil bottles, wine bottles, etc., have a light green color, which is caused by the presence of divalent iron ion impurities in the raw materials used to make glass. Some medicine bottles, beer bottles, and soy sauce bottles are brown-yellow, which is still caused by iron impurities, but not divalent iron ions, but trivalent iron ions.
One of the important raw materials in beer is hops, which gives beer a special bitter taste. The ingredients in hops are light-sensitive and will decompose under the action of ultraviolet rays in the sun, producing an unpleasant "sun odor". Colored glass bottles can reduce this reaction to a certain extent. However, the effect of brown bottles is better than green.
There are colorless and transparent bottled beers on the market, and the hops added in the production are processed. To make colorless glass, the selected raw materials must not contain iron. However, sand, limestone and soda ash in nature always have some iron compounds to a greater or lesser extent. How to eliminate the green color in glass? The chemical method is to add a certain proportion of manganese dioxide to the glass slurry. Manganese dioxide is an oxidant. It oxidizes green ferrous iron ions into yellow ferric iron ions, and manganese becomes purple ferric manganese. Yellow and purple combine to form white, and the glass becomes colorless and transparent. Glass contains different metal compounds and can be "dyed" with various colors. Adding cuprous oxide can produce red glass; adding cobalt oxide - blue glass; adding chromium oxide - green glass