Copper pigments change hue as well as destroy paper carriers (a condition known as <i>Kupferfrass). Investigations of illuminated books and manuscripts as well as painted wallpaper are reviewed; also included are the history of copper containing pigments, the history of problems of discoloration and destructiveness, the decomposition reactions of cellulose. The results of scientific analysis of various copper pigments are cited, and the relationship between the composition of the pigment and its destructiveness to cellulose discussed. An examination of a late eighteenth century Chinese wallpaper confirmed the conclusions of the study. It was discovered that magnesium inhibits the degradation of cellulose. -- AATA