Enlightening yellow in art

Scientists from the University of Perugia (Italy), CNR (Italy), University of Antwerp, the ESRF and DESY, have discovered how masterpieces degrade over time in a new study with mock-up paints carried out at synchrotrons ESRF and DESY. Humidity, coupled with light, appear to be the culprits.

The Scream by Munch, Flowers in a blue vase by Van Gogh or Joy of Life by Matisse, all have something in common: their cadmium yellow pigment. Throughout the years, this colour has faded into a whitish tone and, in some instances, crusts of the paint have arisen, as well as changes in the morphological properties of the paint, such as flaking or crumbling. Conservators and researchers have come to the rescue though, and they are currently using synchrotron techniques to study in depth these sulphide pigments and to find a solution to preserve them in the long run.

“This research has allowed us to make some progress. However, it is very difficult for us to pinpoint to what causes the yellow to go white as we don’t have all the information about how or where the paintings have been kept since they were done in the 19th century”, explains Letizia Monico, scientist from the University of Perugia and the CNR-ISTM. Indeed, limited knowledge of the environmental conditions (e.g., humidity, light, temperature…) in which paintings were stored or displayed over extended periods of time and the heterogeneous chemical composition of paint layers (often rendered more complex by later restoration interventions) hamper a thorough understanding of the overall degradation process.

>Read more on the ESRF website

Image: Some of the mock-up paints, prepared by Letizia Monico. Credits: C. Argoud.

The enigma of Rembrandt’s vivid white

Some of Rembrandt’s masterpieces are at the ESRF for some days, albeit only in minuscule form. The goal: to unveil the secrets of the artist’s white pigment.

Seven medical students surround a dead body while they attentively look at how the doctor is dissecting the deceased. The scene is set in a dark and gloomy environment, where even the faces of the characters show a grey tinge. Strangely, the only light in the scene is that coming from their white collars and the white sheet that partially covers the body. The vivid white creates a perplexing light-reflecting effect. Welcome to painting The anatomy lesson of Dr. Nicolaes Tulp, a piece of art displaying the baffling technique of the impasto, of which Rembrandt, its author, was a master.

Impasto is thick paint laid on the canvas in an amount that makes it stand from the surface. The relief of impasto increases the perceptibility of the paint by increasing its light-reflecting textural properties. Scientists know that Rembrandt achieved the impasto effect by using materials traditionally available on the 17th century Dutch colour market, namely the lead white pigment (mix of hydrocerussite Pb3(CO3)2.(OH)2 and cerussite PbCO3), chalk (calcite CaCO3) and organic mediums (mainly linseed oil). The precise recipe he used is, however, still unknown.

>Read more on the European Synchrotron website

Image: The anatomy lesson of Dr. Nicolaes Tulp, by Rembrandt.

 

Pigments in Oil Paintings Linked to Artwork Degradation

Scientists have observed how lithium moves inside individual nanoparticles that make up batteries.

The finding could help companies develop batteries that charge faster and last longer. Experts have long known that as oil paintings age, soaps can form within the paint, degrading the appearance of the artworks. The process significantly complicates the preservation of oil paintings—and cultural manifestations, which the paintings themselves help to preserve.

“These soaps may form protrusions that grow within the paint and break up through the surface, creating a bumpy texture,” said Silvia Centeno, a member of the Department of Scientific Research at the New York Metropolitan Museum of Art (The Met). “In other cases, the soaps can increase the transparency of the paint, or form a disfiguring, white crust on the painting.”

Scientists do not understand why the soaps take on different manifestations, and for many years, the underlying mechanisms of how the soaps form remained a mystery.

“The Met, alongside our colleagues from other institutions, is trying to figure out why the process takes place, what triggers it, and if there’s a way we can prevent it,” Centeno said.

 

>Read more on the NSLS-II website

Picture: Scientists from Brookhaven Lab and The Met used beamline 5-ID at NSLS-II to analyze a microscopic sample of a 15th century oil painting. Pictured from left to right are Karen Chen-Wiegart (Stony Brook University/BNL), Silvia Centeno (The Met), Juergen Thieme (BNL), and Garth Williams (BNL).