What is copper hydroxide?  What’s the difference between copper hydroxide and copper carbonate?  What is verdigris?

Copper (II) hydroxide is a hydroxide of copper, chemical formula Cu(OH)2.  Copper hydroxide is a light greenish blue or blue-green solid.  Some forms of copper (II) hydroxide are sold as “stable” copper (II) hydroxide, although they may consist of a mixture of copper (II) carbonate and hydroxide.  Copper hydroxide is a strong base, but its solubility in water is so low that it is difficult to observe directly.

Copper hydroxide (II) has been known to man since copper smelting began around 5000 BC, although alchemists were probably the first to make it.  This is easily done by mixing lye with a solution of blue sulfuric acid, both chemicals known from ancient times.

It was produced on an industrial scale in the 17th and 18th centuries to produce pigments such as blue verdant and plum green.  These pigments are used in ceramics and painting.