Patina is a chemical process that happens naturally when metal is left to the elements. The metal oxidizes when exposed to air, much like an avocado (or any fresh surface for that matter) begins to turn brown after being cut. It is a chemical process. Patina is what makes an antique copper pot spot and richen in color.

The word patina derives from the Italianpatinato mean 'a shallow layer of deposit on the surface. ' Now used to refer to any signs of ageing of an antique, whether it be fading, darkening, or oxidising, patination occurs on almost any material.

Figuratively, patina can refer to any fading, darkening, or other signs of age, which are felt to be natural or unavoidable (or both). The chemical process by which a patina forms or is deliberately induced is called patination, and a work of art coated by a patina is said to be patinated.

If you have an old bronze sculpture with a surface that has oxidized and turned green or brown, that coating is called a patina. A patina can appear on anything made of metal. A patina can also be the shiny surface on wooden furniture that you get after years and years of polishing.