A GREENER SOLUTION Investigating the potential use of Green Solvents to remove cellulose nitrate lacquer from silver objects

Abstract: This thesis investigates the performance of non-hazardous solvent substitutes, so called “Green Solvents", for the removal of aged and unaged cellulose nitrate lacquer from silver surfaces. Literature research and preliminary tests resulted in four solvents of interest: ethyl acetate, ethyl lactate, propylene carbonate and dimethyl carbonate. Together with a reference solvent, acetone, the solvents were tested in laboratory experiments to provide answers for the research questions; whether any of the selected green solvents were able to dissolve aged and unaged cellulose nitrate lacquer, if the treatment left any residues and if it affected the silver surface. The experiment was performed according to a standardized experimental design consisting of five solvents and two different methods of removal: cotton swab and poultice. 29 silver coupons were lacquered with “Zaponlack” – a cellulose nitrate lacquer, and 15 of them where artificially aged. Surface abrasion was evaluated using a microscope 200x magnification in rake light, and Infrared Reflection–Absorption Spectroscopy (IRRAS) was used to analyze lacquer residue. The results showed that all solvents were able to dissolve the aged and unaged lacquer to various degrees using the chosen methods, and that the poultice treatment was superior since it removed more dissolved lacquer than the cotton swab treatment, displayed no signs of abrasion to the surface and minimized the quantities of the used solvent. An overall assessment suggested that the carbonates could be the greenest solvents, and providing that financial resources and polymer polarity allow for it, dimethyl carbonate could be of great interest as a substitute solvent within the scope of this thesis. However, ethyl acetate performed better than acetone in both the aged and unaged category, and the solvent’s price and overall greenness assessment reasons it to be suggested as a recommended green solvent for the removal of cellulose nitrate lacquer on silver objects.