A study on the heat distribution and oxidative modification of aged dammar films upon Er:YAG laser irradiation

Chillè, Chiara, Sala, Fernando, Wu, Qiang and Theodorakopoulos, Charis (2020) A study on the heat distribution and oxidative modification of aged dammar films upon Er:YAG laser irradiation. Journal of the Institute of Conservation, 43 (1). pp. 59-78. ISSN 1945-5224

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Abstract

This work shows the impact of one Er:YAG laser pulse to both the surface and bulk of aged dammar varnishes. Tests were performed in fluences ranging from 0.56 to 2.4J/cm2 and pulse durations of 100 and 300μs. Temperature changes upon irradiation were examined by (a) live recordings with an infrared thermal camera, and (b) determining the optical properties of the varnish, which allowed for estimates of the linear absorption coefficient and the temperature rise associated with the laser irradiation. Transmission and Fourier Transform Infrared (FTIR) spectroscopy studies captured increased energy transmissions through varnish films, as well as registering a reduction of hydroxides and carbon–hydrogen bonding as a function of fluence, respectively. FTIR and Differential Scanning Calorimetry (DSC) experimentally determined the absorption coefficient and the specific heat capacity of dammar films, and an overview of laser spots was carried out with Scanning Electron Microscopy (SEM). Evidence on the varnish response to Er:YAG laser irradiation is provided.

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