Washing and cleaning of ancient coins, an alternative methof using ultrasound and chemometry

A cleaning method is proposed, for bronze coins, involving successive washing by deionised water in ultrasonic waves bath, in order to crush and remove both soluble and insoluble corrosion products which are incoherent and not well adhering, thus all the not-protective part of the patina. The total removed incrustations was evaluated by the weight loss of the coin while, for the soluble one, chemical parameters were monitored such as anions, pH, conductivity and redox potential (ORP). All the obtained data were used for the construction of a matrix to be treated by Explorative Data Analysis (EDA) in order to enhance a trend in the washing series and to identify which variables (measures) are more correlated to the identify latent variable.