Physique des matériaux pour éclairer le passé

Materials physics sheds light on the past, from the Bronze Age to the 20th century

Research Article published on 20 February 2026 , Updated on 20 February 2026

When we admire a work of art, do we suspect all the secrets of its creation? The craftsmanship methods that have been used? The efforts that have been made to preserve its original appearance and to keep the artist's vision alive for future generations? These are the kinds of questions addressed by the European Photonic Institute for Non-Destructive Analysis of Ancient Materials (IPANEMA – Univ. Paris-Saclay/CNRS/UVSQ/Ministry of Culture/MNHN) using cutting-edge technologies, the expertise of its scientists, and multidisciplinary collaborations.

Ruins, forests, castles, and oases... The UNESCO World Heritage List includes 1,248 exceptional cultural and/or natural properties, among which today's societies find their roots. However, heritage is not just a question of size: many much smaller objects also have great universal value, whether cultural, historical, aesthetic, scientific, or sociological. These are the materials studied by the heritage science laboratory IPANEMA in Gif-sur-Yvette. Fossils, archaeological artifacts, paintings... the Institute sheds new light on these objects through an in-depth analysis of their composition. Thanks to a multidisciplinary approach combining techniques from materials physics, chemistry, art, and history, it provides answers to questions raised by the humanities and social sciences and contributes to the preservation of this exceptional heritage.

Lighting up matter to characterise ancient materials

In order to understand the unique nature of IPANEMA's research, we first need to define what an “ancient material” is. According to Mathieu Thoury, the laboratory's director, the term “ancient” refers not so much to the age of the material as to its place in a particular era, whether recent or distant. These objects are highly heterogeneous in nature and have the potential to reveal all the processes that have brought them to the present day. The challenge for scientists is therefore to decipher these markers of transformation in order to understand “how time is compressed in matter.”

The IPANEMA building, constructed in 2013 on the SOLEIL synchrotron site, houses facilities to analyse and process data obtained on ancient materials. The synchrotron is a particle accelerator that produces light radiation covering a wide range of wavelengths (from infrared to X-rays, from millimeters to picometers), distributed across several beamlines. These offer a wide variety of analytical methods for researchers, depending on the needs of each study. 
One of the methods used is based on the principle of photoluminescence. The surface of the material being studied is bombarded by a beam of photons. The electrons that make up the material then enter an excited state. As they return to their initial state, they each emit another photon. The modification of the light beam, which results from the interaction of the material with light, is used to characterise the properties of the materials. This principle is applied in a wide range of analysis techniques, covering a broad range of energies and spatial resolutions to achieve specific objectives: characterising the elemental composition, the chemical environment of the atoms, the crystalline structure, etc. 
 

Exploring the painters' palette

Abbaye dans une forêt de chênes. Caspar David Friedrich. 1850.

These techniques are used to analyse the compounds in a pictorial work. For example, the identification of certain pigments and their chemical state provides information about painters' working methods, the modernity of their approach, or the evolution of the work. Some pigments change color as they age, which means that the current appearance of the painting is not what the painter intended at the time. This is the case with smalt, which is a blue pigment that was really popular with painters from the 16th to the 18th century, like Caspar David Friedrich in his painting Abbey in an Oak Forest. Today, this painting looks brown, but the presence of smalt shows that the artist painted it in shades of blue. By combining machine learning with their analysis techniques, scientists have identified the quantities of smalt in each area of the painting and deduced the original color of the work, which they have reproduced through simulation. The impression it gives is completely different!

Paysage au disque. Robert Delaunay. 1906.

Another recent study focuses on the use of the color purple in painting. Until the 19th century, it was a rare color in paintings due to the difficulty and cost of obtaining it from natural materials. The industrial revolution and advances in chemistry led to the development of new inorganic pigments, including cobalt-based pigments, which enriched artists' palettes. Teams from the Laboratory of Supermolecular and Macromolecular Photophysics and Photochemistry (PPSM - Univ. Paris-Saclay/CNRS/ENS Paris-Saclay), IPANEMA, and Chimie ParisTech studied the violet pigments used by Robert Delaunay in his 1906 Self-Portrait and in the painting Landscape with Disc, on display at the Centre Pompidou in Paris. Their analyses revealed the presence of three violet pigments with different shades: cobalt (II) phosphate, whose chemical formula is Co3(PO4)2, cobalt phosphate octahydrate or Co3(PO4)2.8H2O, and cobalt magnesium arsenate, CoMg2(AsO4)2. The latter compound is known to have been used by other artists contemporary with Delaunay, notably Picasso: it is a marker of the modernity of these works.
 

Uncovering yesterday and protecting tomorrow

These techniques are not only applicable to paintings, but also to many other artifacts, such as a copper amulet from the 4th millennium BC, which is now badly damaged. This small object, which is the oldest known to have been made by the lost wax casting technique, was still not fully understood in terms of its metallurgical process. Under the ultraviolet beam of the DISCO light line of the SOLEIL synchrotron, small rods, invisible until then, appeared. These patterns are characteristic of a eutectic, a well-known state in metallurgy. It is a mixture of compounds that melted and then solidified uniformly at a constant temperature. The scientists were thus able to decipher the processes involved in the manufacture and alteration of the amulet. The object was originally made of pure copper, but oxygen was incorporated during the smelting process, forming a layer of cupric oxide. Over time, the copper gradually oxidized, which eliminated the composition differences between copper and copper oxide. Based on the area ratios of the different phases collected from the images obtained, scientists calculated the metal's melting temperature and purity. Analysis of this amulet revealed craft practices dating back thousands of years!

Conservation issues are also central to the work of IPANEMA members. To this end, they develop new instruments and methodologies in collaboration with numerous partners from academic and cultural institutions. This was the case for the PhD thesis of Pauline Hélou de La Grandière, who is an art restorer. Its subject was the restoration of works by Pierre Soulages from the late 1950s. One of the challenges was to design, with two researchers from the Institut d'Optique Graduate School and the Light Matter Institute at Université Lyon I, a device capable of measuring the gloss and mattness values of a work's surfaces without contact. These measurements are essential for monitoring the deterioration of these famous black paintings, in which relief, texture, and the play of light are paramount.

Bringing together a wide range of expertise—physicists, chemists, historians, artists, and art professionals—and drawing on unique tools and methodologies, the research carried out at IPANEMA offers a new understanding of heritage objects, with an eye to both the past and the future.
 

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