1 INTRODUCTION

CORROSION FOUND ON a silver Japanese dragon was brought to the attention of the conservators at the Walters Art Gallery because of its unusual bright blue corrosion deposits. Upon examination, a gray corrosion product which turned black with time was also found in association with the blue corrosion. Samples of both corrosion products were analysed. The blue product was identified by X-ray diffraction as chalconatronite (Na2Cu(CO3)2.3H2O). The black material was identified by X-ray diffraction as silver cyanide (AgCN),1 and the author has previously reported its occurrence in a preliminary article.2 A spot test for silver cyanide is found in Feigl but has not been tried by the author (see Appendix). This paper will discuss the rarity and formation of chalconatronite on a silver object and the tests and methods used to remove the silver cyanide corrosion.