Evaluation of a Dry Method Using Erasers for Silver-Copper Alloy Tarnish Cleaning and Comparison with Traditional Methods

Tarnishing is one of the most crucial issues in the conservation of silver alloy objects. This phenomenon is relevant in the field of cultural heritage artifacts: although the blackish patina protects to a degree against ulterior corrosion effects, it significantly affects the aesthetical features of the artwork. Several different approaches are utilized for cleaning tarnished silver-copper alloy surfaces, including mechanical, chemical, electrochemical methods. The use of lasers is also reported. In this paper a dry approach based on the use of erasers is proposed and compared with traditional methods. The different methods were applied on silver-copper alloy mockups which had been artificially tarnished. They were compared based on the degree of sulfide removal and damage to the silver surface. Diagnostic investigations showed that the use of erasers for silver cleaning resulted in fewer surface modifications compared to traditional mechanical methods with an effective tarnish removal. The proposed method could be broadly considered a low-cost, adjustable, and fast one-step cleaning procedure. Finally, two case studies of application of the technique are reported: cleaning of three Islamic artifacts decorated with silver alloy inlay and of the silver letters on the North Door of the Baptistery of Florence.