A COMPARATIVE STUDY OF SILVER CLEANING ABRASIVES
GLENN WHARTON, SUSAN LANSING MAISH, & WILLIAM S. GINELL
6 FUTURE RESEARCH
THE PRIMARY focus of this research was on the practical effects of abrasives used in polishing systems. A further study on the correlation between the performance of abrasives and their physical characteristics, such as particle size, hardness, and crystal morphology, could provide the groundwork for a better understanding of the polishing characteristics of abrasives. Three additional areas of investigation, which were eliminated from this project due to time constraints, are the effects of abrasive particle fracture in the creation of new cutting edges during polishing; the long-term effects of abrasive particles that become embedded in the silver surface during polishing; and the extent and depth of particle deposition on the silver. Studies of calcium carbonate obtained from other sources would be of interest to identify a product free of large agglomerates. Other variables in the polishing system are the abrasive support cloths and carrier fluids. The accumulation and agglomeration of metallic and abrasive particles in the cloths, as well as the implication of this buildup on the polishing process, should be investigated further. Both the structure of the yarns and hardness of the cloth have been found to play important roles in metallographic polishing processes. Similar studies of nonmetallographic cloths would benefit the field of conservation as well.
Many questions concerning carrier fluids remain unanswered. Further attention should be given to the effects of aqueous/alcohol solutions and other alcohols, such as normal or isopropyl alcohol, to retard the rate of evaporation. Dispersion agents, such as gums, are used in commercial polishing products. It is likely that the addition of a dispersion agent would help keep some of the abrasives in suspension. Such materials could prove of value and should be considered in future studies.
Except for the measurement of silver loss, estimates of the effects of abrasives on silver were subjective and based on visual observations. Although such observations by trained conservators did provide useful and discriminating information, quantitative data for tarnish and scratch are needed to obtain objective numerical data that can be treated statistically. For this purpose, instrumental techniques, such as reflectance spectrophotometry and pattern recognition, can be used to quantify tarnish and scratch.
WE WISH to express our gratitude to the objects conservation staff at the Los Angeles County Museum of Art for their interest and contributions to this project. The conservators at LACMA who treated the silver and responded to the questionnaires were: Laurie German, Andrea Morse, Rosa Lowinger, Sharon Blank, Helene Gillette, Gretchen Anderson, David Rasch, Susan Lansing Maish and Glenn Wharton. We also appreciate the suggestions and criticism provided by Andrew Lins, Wase Ahmed, Terry Weisser, Don Heller, Shelley Reisman Paine, Timothy Schroder, and John Twilley. We would also like to thank Donald Dietrich, Michael Schilling, and Jesse Lumsden for the SEM and microprobe, XRF, and Auger analyses, respectively, and Terry Reedy, who performed statistical analyses of the data. We wish to express our thanks to Pieter Meyers, Frank Preusser, and Jerry Podany for their continued interest and support during this project. In addition, one of us (G.W.) would like to acknowledge the financial assistance provided by the Andrew W. Mellon Foundation and the Getty Conservation Institute during the course of this work.