Copper corrosion is the destruction of paper and parchment from verdigris, a basic copper acetate. Since the middle ages verdigris has been used in pigment for illustrations in the form of dark blue green monocline prismas soluble in water. As with ink corrosion, paintings disintegrate because of the presence of acid and corrosive compounds. Symptoms range from discolouring of areas painted green to the decomposition of the colour pigment and the paper on which it is painted. >> More