During analysis of the pigments, grounds, and previous conservation consolidants used on two Taoist paintings in preparation for a current conservation treatment, calcium oxalate hydrates were found in most of the samples taken from one of these scroll paintings. These findings prompted examination of the third painting; both copper and calcium oxalates were found on the last two paintings. Copper oxalate appeared as an alteration product of the original azurite and malachite pigments. The analytical procedures are described in detail. The widespread distribution of the oxalates suggested an overall, nonspecific process of oxalate introduction. Considers three possibilities for the source of this oxalate contamination. -- AATA