Minimal invasive control of paintings cleaning by LIBS

• LIBS stratigraphic analysis/cleaning of mock-up painting.
• Comparative study using VIS and UV nanosecond laser was made.
• Laser beam parameters are provided for fine depth resolution in varnish removal.

In cultural heritage restoration and conservation, it has been proved that LIBS is an appropriate technique for pigments identification, analysis of multilayered paintings, and quantitative analysis of ancient materials. Generally, experiments involving the use of laser for paint cleaning and LIBS in order to identify the composition of the removed material are made. Here, we report LIBS studies on mastic and dammar varnishes removal using visible (532 nm) and UV (266 nm) laser pulses (5 ns) with fluences in the range 0.6–4.4 J/cm2. The studied varnish layers were on-purpose painted on glass supports or were part of several mock-up samples having dammar or mastic as final layer – gold foil, yellow ochre or cobalt blue egg tempera as painting layer – chalk or acrylic ground as link to an wooden support. LIBS was used to monitor the laser induced stepwise selective removal of the layers and to analyze their composition.