The analysis of pictorial art sometimes begins far from the brushstroke: a painting is illuminated with X-rays, pointed with a Raman laser or photographed in bands of light that no human eye perceives. Thanks to these techniques, A discarded drawing, a repaint, may appear beneath the visible surface.the trace of an unusual pigment or the imprint of a hand other than that of the master. The painting then stops being a fixed image and becomes an archive of decisions.
Recent technical studies of works of art show that science can still provide new evidence about the conception, execution and meaning of these pieces. Let’s see how it has been possible with the Salvator Mundi, a mural by Diego Rivera, the Vatican’s Constantine Room and rock art from Sulawesi.
The use of new technologies is rewriting the history of art as we knew it.
An invisible world under the layers of paint
What’s underneath Las Meninas of Velázquez, of The wounded deer of Frida Kahlo or The witch by Salvator Rosa? Some technologies are capable of showing what is hidden in the brush strokes of a painting. The radiography of paintings records the differences in X-ray absorption: pigments with heavy elements, such as lead or mercury, appear with greater contrast and reveal changes in compositionnails, supports or repainted areas. It does not identify an artist, and its results can become ambiguous when several materials respond similarly.
Other techniques, such as infrared reflectance, penetrate certain layers and reveal preparatory drawings, that is, the sketch drawn before applying color. Ultraviolet light, for its part, makes visible the fluorescence associated with varnishes, repaints and old restorations.
Other techniques, such as infrared reflectance, pierce certain layers and reveal preparatory drawings, the sketch drawn before color is applied.
The technical anomaly of the Constantine Room
During the restoration of the Vatican Museums’ Constantine Room, a technical study detected a telling oddity. It was discovered that two allegorical figures, Justice (Iustitia) and Courtesy (Comites), were not frescoedlike the rest of the room, but directly in oil on the wall. This experimental technique is risky, since the application of oil paint on the wall poses serious problems of adhesion and conservation. This anomaly has been interpreted as the material indication of a rehearsal phase attributed to Rafael’s environment.
From recipe to practice
The identification of pigments and the establishment of artistic authorship of a work are much more solid when they combine several techniques. Thus, spectroscopy studies how a substance absorbs, emits or disperses radiation: X-ray fluorescence (XRF) reports on the chemical elements present, while Raman spectroscopy provides molecular and mineralogical information.
Painted between 1922 and 1923, the mural The creationDiego Rivera’s first major work, offers a notable example. Tradition described it as an encaustic painting, made with molten beeswax and resins. However, the microchemical analysis published in 2026 in ACS Omega by Aguilar-Rodríguez and his team detected biomarkers compatible with copal resin. However, no evidence of beeswax was found in the samples examined.
The discrepancy between the described recipe and material practice may be due to a reformulation of the artistto a selective degradation of the components or to sampling limitations. In any case, this specific case suggests that what an artist claims to do and what he actually does do not always coincide.
A microchemical analysis of the mural The creationby Diego Rivera, detected biomarkers compatible with copal resin, but did not find any evidence of beeswax in the samples examined.
Who painted it? Crystallography and the limits of plausibility
Crystallography deals with the arrangement of atoms in crystalline solids and can identify mineral structures. Its most commented use in an artistic context came with the Salvator Mundiattributed to Leonardo da Vinci. In an article published in 2026 in npj Heritage ScienceJuan Manuel García-Ruiz and Dianne Modestini examined the tiny spots represented on the transparent orb holding the figure of Christ.
Their interpretation is that these millimeter specks would not represent simple air bubbles in the glass, but rather would reproduce anisotropic fluid inclusions, that is, small cavities with liquid trapped inside a crystal, typical of a quartz or rock crystal sphere. The polygonal shapes and their correlated orientation would point to the symmetry of a real crystal. If so, the painting would have represented a mineralogical phenomenon more than three centuries before science described it.
In this case, crystallography only establishes which painted shapes are compatible with certain crystalline structures. It is, therefore, a plausibility argument based on geometry. The attribution of Salvator Mundi It still depends on style, provenance, restoration history, and comparison with documented works, but using other disciplines to read the painting provides a broader framework for its interpretation.
According to research, the millimeter specks of the orb of the Salvator Mundi They would reproduce small cavities with liquid trapped inside a crystal, typical of a quartz or rock crystal sphere.
The limits imposed by the rock
Prehistoric art clearly illustrates the limits of these scientific techniques applied to art. A research published in Nature in 2026 and centered on Liang Metanduno, Muna Island (Southeast Sulawesi), dated a handprint to a minimum age of 67,800 years. The technique used, uranium-thorium series dating, measures the time elapsed since the radioactive decay of the uranium present in the calcite. The technique, therefore, allows us to date the layer of calcite that covers the paint, but not the pigment. The figure indicates that the hand was printed at least 67,800 years ago, but does not establish the exact moment of its execution.
Even artificial intelligence, the most recent tool, operates under this logic of caution. Algorithms applied to microscopic maps of texture and surface topography can compare brushstroke patterns and help locate matches, but they produce probabilities and correlations, not verdicts. Its results only make sense when they are contrasted with the knowledge of the conservator, the material history of the work and the rest of the evidence. Hence, the laboratory does not replace the expert eye: it only extends it.
