The deterioration of copper pigments and their detrimental effects upon the cellulosic support are examined. Both paper and the copper compounds studied are stable at ambient conditions and higher temperatures used in the laboratory but together they interact in such a way that the green pigmentation turns to brown and the cellulose is weakened. Verdigris undergoes conversion to copper sulfite upon absorption of gaseous SO₂, and this has a color ranging from white to red depending upon its state of hydration. Both chlorine and sulfur are found in deteriorated areas of copper pigmentation but the state of combination is difficult to assess since x-ray diffraction is not usually successful. It is suggested that Fehling's reaction is at least partly responsible for the color change since the degree of crystallinity of the cellulose is reduced as time passes. The reducing carbohydrates created may then cause conversion of copper H to brown copper I oxide. See also 17-1070. -- AATA