(from the article `art conservation and restoration`) ...regularly used, as was chemical stripping (which dissolved the mineral alteration products) and electrochemical reduction, which also stripped the ... Patinas on metals are caused by the corrosive action of chemicals. Sculpture that is exposed to different kinds of atmosphere or b... Found on http://www.britannica.com/eb/a-z/p/28
The surface appearance (as a coloring or a mellowing) of something grown beautiful through a lengthy passage of time or extended use. The rosy gold surface on early American gold coins is a good example of patination. Found on https://www.encyclo.co.uk/local/22578