Rapid initial dimensional changes in wooden panel paintings due to simulated climate-induced alterations monitored by digital coherent out-of-plane interferometry

Climate and environmental change may provoke constant microscopic dimensional alterations to organically composed works of art. The complexity of alterations obstructs the classification of destructive effects and sustainable strategies for preservation, and systematic investigation of change requires safe inspection tools, repeatable procedures and non-perturbing approaches. In this paper, a state-of-the-art description on the dimensional monitoring tools for the assessment of the effects of climate fluctuations in paintings is given. Rapid initial start-up reactions of alteration processes that may simulate endangered conditions, which may be encountered during transportation of works of art, are studied. The case of wooden panel paintings is considered here as panels are representative models of inhomogeneous organic construction. The effect of the surface movement of panel painting surfaces due to simulated changes in temperature and relative humidity is characteristic of structural deterioration and as such these effects are primarily monitored in the start-up of the reaction process. The environmentally-provoked spatial alteration is recorded in full-field surface coordinates using optical coherent out-of-plane digital interferometry in a geometry utilizing holographic speckle patterns. Results demonstrate the suitability of the method to follow the start-up simulated process in real time directly from the work of art and to follow the rate of reaction towards equilibrium. The effectiveness of the full surface assessment provided in real time is presented and provides significant advantages compared to alternative techniques which are based on fragmented solutions.