The triptych called "The Master of Mills" nestled in the sacristy of the cathedral of Moulins (Allier) is recognized worldwide as a masterpiece of the early Renaissance. In early November 2022, he left the cathedral to join the workshops of the Centre de recherche et de restauration des musées de France (C2RMF) where he will be restored.
6.The triptych says "of the Master of Mills": his radiography
Arrived in November 2022, the triptych says "of the Master of Mills" at Centre de recherche et de restauration des musées de France (C2RMF) had to wait some time and acclimatize before being taken out of the transport crates. The first scientific observations and investigations were then able to begin.
The scientific imaging file, carried out in situ in 2018, was supplemented by an x-ray of the entire triptych because only a partial x-ray was carried out in 1963 by the laboratory.
The panels were radiographed successively by a radiologist specialized in heritage objects in a secure space, a shielded casemate preventing X-ray scattering. They were positioned and secured on an easel located three meters from the radiation source with the help of installers. Radiographic films were placed on the reverse side of the works and then exposed to X-rays.
Radiography is a transmission imaging technique.
It makes it possible to obtain an image whose contrast depends on both the thickness and the attenuation coefficient of the structures crossed.
More simply, the clearer the result, the denser the material and the more kilovolts it takes to cross it.
It is for this reason that an additional exposure with a higher kilovoltage was made at the angles of the frame to properly visualize the internal means of fixation.
The radiography of the Triptych of the Master of Mills has thus made it possible to visualize the internal structure of wood panels, frames but also assemblies for a better knowledge of the work for its restoration.
Moreover, radiography has also made it possible to obtain information on the technique of painting and on the state of the pictorial layer and wood panels.
The work was then examined by two engineers from the Research and Restoration Department who determined the list of colors to be analyzed by X-ray fluorescence. The objective was to have a first level of information on the nature of the original pigments and repaints.
X-ray fluorescence analysis
Understanding the structure of panels is one thing, but understanding the material is another. X-ray fluorescence spectrometry is a technique that uses X-rays.
The reaction results from a restitution, in the form of X-rays, of the interaction of X-rays and the exposed material. This reaction being specific to each element, it is possible to identify the constituent elements of the works and subsequently the pigments used by the artists.
To be noted! The elements detected depend on their density, for example, the presence of lead, a very dense element, will mask the elements below.
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©C2RMF / Philippe Dureuil