Spherical Copper Resinate on Coromandel Objects: Analysis and Conservation of Matt Green Paint

An unusual green pigment was found on a seventeenth-century kuan cai (Coromandel) lacquer screen at the Victoria and Albert Museum, London. The particles are perfectly spherical and translucent, with the appearance of green fish roe. Analysis revealed that the pigment is a copper resinate, produced by reacting a copper salt with a resin, probably one from a Pinus species. The binding medium for the pigment is proteinaceous. The unusual spherical morphology of the particles results from the method of manufacture. A pigment with the same microscopic appearance was also found on two other Coromandel objects from the same collection. In light or olive green areas, where the pigment is mixed with lead white, the paint is glossy and well preserved. In contrast, in the dark green areas where the pigment was used alone, the paint is matt and powdery and there is significant paint loss and abrasion. The problem of consolidation of the powdery paint, while still preserving the matt appearance of the surface, was resolved by the use of immiscible solvents and consolidant.