from Wikipedia: en.wikipedia.org/wiki/Verdigris 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). Since it was used as a pigment in paintings and other art objects (as green color), it was required by artists in 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 It was originally made by hanging copper plates over hot vinegar in a sealed pot until a green crust formed on the copper.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.[4] The chemical reaction exhibited between wine and copper to produce verdigris may be related to wines own oxidization 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.
Posted on: Sun, 28 Dec 2014 00:37:24 +0000