Verdigris  Verdigris is the common name for a green pigment obtained through the application of acetic acid to copper plates or the natural patina formed when copper, brass or bronze is weathered and exposed to air or seawater over time. It is usually a basic copper carbonate (()2), but near the sea will be a basic copper chloride (Cu2(OH)3Cl). If acetic acid is present at the time of weathering, it may consist of copper(II) acetate. The name "verdigris" comes from the Middle English "vertegrez", from the Old French "verte grez", an alteration of "vert-de-Grèce" ("green of Greece"). The modern French spelling of this word is "vert-de-gris" ("green of grey"). It was used as a pigment in paintings and other art objects (as green color), mostly imported from Greece. It was originally made by hanging copper plates over hot vinegar in a sealed pot until a green crust formed on the copper. Another method of obtaining verdigris pigment, used in the Middle Ages, was to attach copper strips to a wooden block with acetic acid, then bury the sealed block in dung. A few weeks later the pot was dug up and the verdigris scraped off. In eighteenth-century Montpellier, France, it was manufactured in household cellars, "where copper plates were stacked in clay pots filled with distilled wine." The verdigris was scraped off weekly by the women of the household. The chemical reaction exhibited between wine and copper to produce verdigris may be related to wine's own oxidation process. Another method, used in the early nineteenth century, had to do with reacting copper sulfate solution with solutions of lead, barium, or calcium acetate. Their sulfates are insoluble, forming precipitates and leaving the copper acetate in solution. Natural or artificially created coatings of verdigris are commonly used as a patina to protect copper or bronze objects, especially in architecture. It is also used industrially as a fungicide, a catalyst for organic reactions, and in dyeing ("The Merck Index ", Ninth Ed., 1976). Verdigris has also been used in medicine. The vivid green color of copper(II) acetate made this form of verdigris a much used pigment. Until the 19th century, verdigris was the most vibrant green pigment available and was frequently used in painting.