The Impact of Accelerated Light Ageing on MS3 for Use as a Picture Varnish

This study provides an evaluation of MS3, a reduced polycyclohexanone resin, with key considerations for use as a picture varnish including solubility, removability, colour, and gloss and the stability of these factors. MS3 was first produced in 2016 as a replacement for the discontinued MS2A resin which was widely used as a conservation-grade picture varnish. Films of MS3 resin were artificially aged using UV-containing and UV-filtered light, representing the effects of daylight filtered through glass, and indoor museum lighting conditions respectively. Changes in colour and gloss of light-aged samples vs. control samples were measured, and solubility/removability was evaluated using selected solvents applied by hand-rolled swabs. FTIR spectroscopy was used to explore chemical changes of the varnish films following light ageing with respect to control samples. Empirical observations were made regarding the handling properties of MS3 dissolved in Stoddard solvent, and its behaviour as a retouching medium and varnish. The results suggest that MS3 exhibits a slight yellowing and a moderate increase in the polarity of solvent required for removal. No significant colour or solubility changes were observed in MS3 varnish films artificially aged using non-UV light. The results suggest that MS3 is a good substitute for MS2A resin for use as a picture varnish or retouching medium, based on the parameters measured.