Ordinary glass is made of quartz sand, soda ash and limestone. It is a mixture of silicate. People first made out of the glass which is some poor transparency,and which begin to make with some color of the small glass. Its color is not people consciously added to, but the raw materials used impure, mixed into the results of impurities.
Then the color of the glass is only used to do decorations, the request is not high, people just accidentally produced a color glass. But today we require the color of the glass has a very high scientific requirements, which only opened the glass after the secret, and that can be made out.
the picture above shows blue glass beads
After research, it was found that if the ordinary glass ingredients by adding 0.4 ~ 0.7% of the coloring agent, you can make the glass with a color. Coloring agents are mostly metal oxides. We already know that each metal element has its own unique "spectral characteristics", so different metal oxides can show a different color. If these oxides are added to the glass ingredients, the glass is colored. Such as adding chromium oxide (Cr2O3), the glass is green; adding manganese dioxide (MnO2), the glass is purple; adding cobalt oxide (Co2O3), the glass is blue, steel workers and welding workers to protect the eyepiece is used this made of glass.
In fact, the color of the glass depends not only on the added colorants, but also by melting the temperature and the nature of the furnace to adjust the elemental valence, so that the glass presents a different color. Such as copper in glass, if the presence of high-priced copper oxide,the glass appears blue and green; When the low cost of cuprous oxide (Cu2O) is present, the glass is red. Sometimes, burning once can not make the glass show excellent, and then a second heating in order to make the glass show color. Precious gold-red glass is the case, it is in the ordinary glass ingredients by adding a trace of gold into the burning. After the first firing, gold is distributed in the form of atoms in the glass, when the glass does not show color; when heated again to near softening temperature, where the gold atoms are aggregated into colloidal particles, then the glass appears to the beautiful red.
Now, people use the rare earth oxide as a colorant made a variety of advanced color glass. Mixed with rare earth elements of the color glass, bright color, bright color, and even in different light to change the color. For example, neodymium oxide in the glass there is such a feature, it was purple in the sun, under the fluorescence was blue and purple, very beautiful.