[LUM#11] At the heart of a work of art

[LUM Magazine] - Published on December 20, 2019 in Heritage, Science-Society

Humidity, temperature variations, the passage of time... in museums, paintings on wooden supports are put to the test. To better understand the movements of wood and thus better preserve these works, Delphine Jullien, a researcher at the Mechanics and Civil Engineering Laboratory (LMGC), has designed a very special display case installed at the Fabre Museum.

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Testimonies to a sometimes distant past, works of art span the centuries and are not immune to the ravages of time. Paintings on wood, for example, are subject to the natural deformations of this material, which can sometimes alter the works. To better preserve this heritage, curators are turning to... researchers. In particular, the wood team at the Laboratoire de mécanique et génie civil de Montpellier(LMGC) has solid expertise in this field, having already worked on the famous Mona Lisa, in collaboration with the PPRIME institute in Poitiers, and GESAAF at the University of Florence (Italy).

This time these researchers are examining The Holy Trinity Crowning the Virginon display at Montpellier's Musée Fabre. Delphine Jullien explains: " This ^15th-century painting is mounted on a set of four oak boards, fitted with a frame and parquet on the back. This prevents movement of the wood due to variations in environmental humidity, which has led to the appearance of cracks altering the paint layer.

To better understand the behavior of wood, the researcher and her team set up a real laboratory in the heart of the museum, facing the public. " The painting is placed in an airtight climatic showcase where it is subjected to hygrometric variations, from 53 to 63% relative humidity ".

A high-precision balance measures the weight variation of the panel and deduces the mass of water absorbed by the wood. A system of cameras reconstituting the work in three dimensions and "deformometric" sensors continuously measure wood movements and panel deformations.

" These data will enable us to quantify and better understand the movements of a painting on wood, and thus to work with restorers to propose solutions for better conservation," emphasizes Delphine Jullien.