Green
Pigments, food coloring and fireworks

Many minerals provide pigments which have been used in green paints and dyes over the centuries. Pigments, in this case, are minerals which reflect the color green, rather that emitting it through luminescent or phosphorescent qualities. The large number of green pigments makes it impossible to mention them all. Among the more notable green minerals, however is the emerald, which is colored green by trace amounts of chromium and sometimes vanadium. Chromium(III) oxide (Cr O), is called chrome green, also called viridian or institutional green when used as a pigment. For many years, the source of amazonite 's color was a mystery. Widely thought to have been due to copper because copper compounds often have blue and green colors, the blue-green color is likely to be derived from small quantities of lead and water in the feldspar. Copper is the source of the green color in malachite pigments, chemically known as basic copper(II) carbonate.

Verdigris is made by placing a plate or blade of copper, brass or bronze, slightly warmed, into a vat of fermenting wine, leaving it there for several weeks, and then scraping off and drying the green powder that forms on the metal. The process of making verdigris was described in ancient times by Pliny. It was used by the Romans in the murals of Pompeii, and in Celtic medieval manuscripts as early as the 5th century AD. It produced a blue-green which no other pigment could imitate, but it had drawbacks: it was unstable, it could not resist dampness, it did not mix well with other colors, it could ruin other colors with which it came into contact, and it was toxic. Leonardo da Vinci, in his treatise on painting, warned artists not to use it. It was widely used in miniature paintings in Europe and Persia in the 16th and 17th centuries. Its use largely ended in the late 19th century, when it was replaced by the safer and more stable chrome green. Viridian, as described above, was patented in 1859. It became popular with painters, since, unlike other synthetic greens, it was stable and not toxic. Vincent van Gogh used it, along with Prussian blue, to create a dark blue sky with a greenish tint in his painting Café Terrace at Night.

Green earth is a natural pigment used since the time of the Roman Empire. It is composed of clay colored by iron oxide, magnesium, aluminum silicate, or potassium. Large deposits were found in the South of France near Nice, and in Italy around Verona, on Cyprus, and in Bohemia. The clay was crushed, washed to remove impurities, then powdered. It was sometimes called Green of Verona.

Mixtures of oxidized cobalt and zinc were also used to create green paints as early as the 18th century.

Cobalt green, sometimes known as Rinman's green or zinc green, is a translucent green pigment made by heating a mixture of cobalt (II) oxide and zinc oxide. Sven Rinman, a Swedish chemist, discovered this compound in 1780. Green chrome oxide was a new synthetic green created by a chemist named Pannetier in Paris in about 1835. Emerald green was a synthetic deep green made in the 19th century by hydrating chrome oxide. It was also known as Guignet green.

There is no natural source for green food colorings which has been approved by the US Food and Drug Administration. Chlorophyll, the E numbers E140 and E141, is the most common green chemical found in nature, and only allowed in certain medicines and cosmetic materials. Quinoline Yellow (E104) is a commonly used coloring in the United Kingdom but is banned in Australia, Japan, Norway and the United States. Green S (E142) is prohibited in many countries, for it is known to cause hyperactivity, asthma, urticaria, and insomnia.

To create green sparks, fireworks use barium salts, such as barium chlorate, barium nitrate crystals, or barium chloride, also used for green fireplace logs. Copper salts typically burn blue, but cupric chloride (also known as "campfire blue") can also produce green flames. Green pyrotechnic flares can use a mix ratio 75:25 of boron and potassium nitrate. Smoke can be turned green by a mixture: solvent yellow 33, solvent green 3, lactose, magnesium carbonate plus sodium carbonate added to potassium chlorate.
startend:end_checker