Physical change of paintings on a textile base caused by mechanical loads: Investigations on origin and development of damage

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Due to the increase in special exhibitions in the public and private sectors, the number of art transports has risen remarkably in recent years. Occasionally, that leads to obvious damage to the fragile objects, but most of all that leads to microscopically small changes as well. Despite extensive attempts to completely isolate mechanical stresses from pieces of art, that is impossible to achieve completely in practice. Aging of artwork during transport cannot be completely ruled out. It is therefore desirable to know the expected damage in advance, or at least to be able to estimate it beforehand. To the current state of research, however, this is only insufficiently possible. Therefore, the aim of this interdisciplinary project is to make it possible to predict damage to paintings with textile bases subject to mechanical stresses and to enable the assessment of damage from an objective perspective. Essentially, two steps are necessary for this: Firstly, the paint layer motion must be determinable before transport, and secondly, it must be possible to deduce the damage caused by the paint layer motion considering the texture of the particular artwork. The first milestone is making the spatially distributed paint layer movement calculable from the mechanical immission, i.e. the frame motion. The agreement between the mathematical model and the real object behavior is evaluated based on real transports and their accurate reproduction in the laboratory under stable climatic conditions. Experimental identification processes are developed for real paintings, which allow the mathematical models to be parameterized and tuned, however, with attention to the least possible stress on the paintings. This way, the paint layer motion for an already completed, as well as a planned transport can be determined in advance - a paint layer motion estimator is established. This enables to dynamically design painting mounts in transport crates in terms of minimal paint layer motion. The second milestone is to use the predicted paint layer motion in order to predict the amount of damage and to systematically distinguish it from other sources of damage. For this purpose, the relationship between materiality/layering and the amplitude/number of cycles required for damage is determined experimentally in dynamic fatigue tests and summarized in stress-cycle diagrams. The damage is captured optically. The tests take place on specially shaped test specimens that are particularly manufactured in this project or are obtained from paintings of little or no artistic value. In order to estimate the damage on real paintings the spatially distributed motion of the paint layer is compared to the stress-cycle diagram using cycle-counting methods and rainflow-counting algorithms - a damage estimator is established.