Appearance-based evaluation of varnish removal methods in gilded surfaces

This paper outlines the use of bidirectional reflectance measurements for thecharacterisation and evaluation of appearance changes in gilded surfaces causedby varnishing and cleaning. Oil and water gilding mock-ups representative of a15th century panel painting were varnished, and a selection of four varnishcleaning methods were applied. By measuring the bidirectional reflectance of thesamples, their appearance is modelled and evaluated according to perceptualgloss attributes. Three main perceptual groups are found for each gilding type:unvarnished, varnished, and cleaned surfaces. Finally, the cleaning method mostappropriate, in terms of appearance change, for cleaning a varnished, gildedsurface is solubilisation by applying a compress.