A novel approach for high selective micro-sampling of organic painting materials by Er:YAG laser ablation

A new approach for sampling micro-amounts of mainly organic materials from thin layers of a painting is described. A pulsed Er:YAG laser system operating at 2.94 µm was used for collecting ablate materials. The experimental ablation conditions optimised on reference paint layer samples resulted in using laser energy lower than 20 mJ at 15 pulses/s (pps) assisted by water/ethanol mixtures. The ablate materials condensed on glass coverslips were characterised by Fourier transformed infrared spectrometry (FT-IR) and gas chromatographymass spectrometry (GC-MS) procedures. The results showed that the laser energy did not significantly degrade the ablate organic material collected which can be successfully identified. The procedure, tested and calibrated on reference paint layer specimens, was applied for the sampling and characterisation of two old paintings. The presence of overpaintings consisting of egg and Venice turpentine in one case, and of “beverone” over a varnish (linseed oil and Venice turpentine) in the other one was highlighted. © 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.