A Chemical Investigation of the 18 Day Creation of Lead Oil.

Abstract

Lead oil is a paint medium used by conservators to restore oil paintings authentically to their original brilliance. Lead oil is a combination of linseed oil and lead oxide. Upon heating the solution darkens in color and must sit for an 18-day incubation period until it becomes colorless. Once colorless the solution is ready to be used in art restoration. Little is known about the chemical changes that occur during the 18-day incubation period. Two lead oil solutions, 5% and 10%, were sampled daily for 18 days and prepared for analysis by GFAAS using an acid digestion. Other analyses included FT-IR, GC/MS, and UV-VIS. The FT-IR spectra showed a decrease in vinyl hydrogens of the linseed oil, presenting the initial indication of polymerization by oxidation of carbon-carbon double bonds. Although it was hypothesized that lead concentrations would remain constant over the 18-day incubation period, under the present conditions the results for both lead solutions show a decreasing trend in lead concentration, followed by a plateau in lead concentration ranging from 10-20 mg Pb/kg. Possible reasons for the decreasing trend are postulated.