Initial investigation into the effect of varying parameters in using an Er:YAG laser for the removal of brass-based overpaint from an oilgilded frame

The removal of brass-based overpaint, applied during previous restoration, from an oilgilded frame by the application of solvents can be challenging and difficult to control due to the often similar solubilities of the paint and oil gilding. In this study, Er:YAG laser radiation (2940nm) has been used to remove brass-based overpaint from a discoloured overpainted oil-gilded frame. Tests have been systematically carried out to investigate the effect of changes to: (1) laser parameters (fluence; number of pulses; pulse duration; repetition rate), and (2) choice of pre-wetting agent (water; isopropyl alcohol; acetone) on the removal process. Observations of the irradiated surfaces revealed that the thermal interaction between laser radiation and the overpaint led to decomposition of the overpaint binder which weakened the paint sufficiently to enableremovalusingacotton swab.Byusing acetoneas a pre-wettingagent,the overpaint was removed from a small area of the frame by 20 pulses at 0.8J/cm2 (80µs pulse duration; 1Hz) revealing the gold leaf. This investigation demonstrates the potential for Er:YAG laser radiation in the controlled removal of brass-based overpaint from gilded woodandtherequirementforfurtherworktooptimisetheremovalprocessandcharacterise the ‘cleaned’ surface.