The color of glass not only depends on the coloring agent added, but people also adjust the valence of elements through the melting temperature and the properties of the furnace flame, making the glass appear different colors. For example, copper in glass appears blue-green when high priced copper oxide is present; When low priced cuprous oxide (Cu2O) is present, the glass appears red. Sometimes, melting once does not make the glass display well, and a second heating is needed to make the glass show its color. The precious golden red glass is like this, it is made by adding a small amount of gold to ordinary glass ingredients and firing them.
How did these beautiful glass colors come about?
After research, it has been found that adding 0.4-0.7% coloring agent to the ingredients of ordinary glass can bring color to the glass. Most coloring agents are metal oxides. We already know that each metal element has its unique "spectral characteristics", so different metal oxides can exhibit different colors. If these oxides are added to the glass ingredients, they will color the glass. For example, adding chromium oxide (Cr2O3) causes the glass to turn green; Adding manganese dioxide (MnO2), the glass turns purple; Adding cobalt oxide (Co2O3), the glass appears blue, and the protective goggles used by steelworkers and welders are made of this type of glass.
In fact, the color of glass not only depends on the coloring agent added, but people also adjust the valence of elements through the melting temperature and the properties of the furnace flame, making the glass appear different colors. For example, copper in glass appears blue-green when high priced copper oxide is present; When low priced cuprous oxide (Cu2O) is present, the glass appears red. Sometimes, melting once does not make the glass display well, and a second heating is needed to make the glass show its color. The precious golden red glass is like this, it is made by adding a small amount of gold to ordinary glass ingredients and firing them. After the first melting, gold is distributed in atomic form in the glass, and the glass does not show any color at this time; When heated again to a temperature close to softening, the gold atoms in it aggregate into gel like particles, and the glass exhibits a beautiful red color.
Now, people have made various advanced colored glasses using rare earth element oxides as coloring agents. Colored glass doped with rare earth elements has a clear and bright color tone, and even changes color under different lighting conditions. For example, neodymium oxide glass has this characteristic, it appears purple red under sunlight and blue purple under fluorescence, which is very beautiful. There is a type of glass that changes color with the intensity of light, and people use it as lenses for glasses and window glass for houses. Using this type of glass as window glass can maintain a certain level of brightness indoors, and there is no need to use curtains to block the sun, so some people call it "automatic curtains". It can also block the passage of ultraviolet rays in sunlight. After installing this type of glass in libraries, libraries, and museums, it can protect books and cultural relics from UV damage.
In addition to rare earth elements, adding tungsten and platinum directly to glass can also make color changing glass.