The excimer laser ablation of picture varnishes

Charalampos Theodorakopoulos, The excimer laser ablation of picture varnishes: an evaluation with reference to light-induced deterioration, Tese de Doutoramento, Royal College of Art, 2005

This thesis provides a study on the laser cleaning of three painting coatings (dammar, mastic and copal oil varnishes) with KrF excimer laser (248 nm) nanosecond pulses. Unlike previous studies on the photochemical laser ablation of polymers, most of the attention herein is paid to the contribution of the chemistry to the process across the depth profiles of the aged varnishes. Such an approach was essential because consecutive laser pulses interact with subsequent depths across the thickness of the same ablated film. Moreover, in laser cleaning applications for conservation the remaining material is more important than the material ablated. The coatings tested were clearly separated into two groups: (i) natural resin ‘spirit’ varnishes, which are initially dissolved in a solvent for the formation of the final film and (ii) pre-polymerised resin-oil varnishes, which undergo a strong heating manufacture towards the formation of viscous and insoluble films.

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