CLEANING OF A NINETEENTH-CENTURY PAINTING WITH DEOXYCHOLATE SOAP: MECHANISM AND RESIDUE STUDIES

Abstract

AbstractResin soaps as developed by Richard Wolbers were used to remove old varnishes from a nineteenth-century oil painting. To assess the cleaning effect of a water-soluble formulation of deoxycholate soap, investigations using gas chromatography/mass spectrometry (GC/MS) were carried out. GC/MS analyses allowed identification of the components of the varnishes as well as the varnish components remaining after cleaning. At least one varnish of the oil type and one of the resin type could be identified on the painting. Although the formulation had been chosen to remove resin varnishes, all resinous components of the varnishes remained unchanged in the residue whereas oily components, especially free fatty acids, were removed by the deoxycholate soap. Moreover, it can be denlonstrated that residues of soap formulations will reInain on the surface of the painting after the cleaning procedure.