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Web Date: January 18, 2011

A Rembrandt Painting Reveals Its Secrets To Imaging Mass Spectrometry

Art Analysis: Researchers discover that the artist added wheat starch to his paints
Department: Science & Technology, Government & Policy
Keywords: TOF-SIMS, imaging mass spectrometry, Rembrandt, starch, paint
ANALYZING REMBRANDT
Researchers used imaging mass spectrometry to analyze the molecular details of the oil painting Portrait of Nicolaes van Bambeeck.
Credit: Royal Museums of Fine Arts (Brussels), inv. 155, © IRPA-KIK, Brussels.
Rembrandt1
 
ANALYZING REMBRANDT
Researchers used imaging mass spectrometry to analyze the molecular details of the oil painting Portrait of Nicolaes van Bambeeck.
Credit: Royal Museums of Fine Arts (Brussels), inv. 155, © IRPA-KIK, Brussels.

Art conservators and historians study works of famous artists to, among other things, discover the artists' secret paint recipes. Now, using an imaging mass spectrometric technique, European researchers have uncovered an ingredient never before seen in work by the renowned 17th-century Dutch artist Rembrandt van Rijn (Anal. Chem., DOI: 10.1021/ac1017748).

In 2009, Belgium's Royal Institute for Cultural Heritage, a science institute dedicated to art restoration and study, restored Rembrandt's 1641 painting of a rich wool merchant, The Portrait of Nicolaes van Bambeeck.  During the process, researchers studied the painter's techniques and materials using several conventional paint analysis approaches, including scanning electron microscopy, infrared spectroscopy, and liquid chromatography.

"These analyses mostly matched previous studies made on the Rembrandt painting," says analytical chemist Pascale Richardin at the Center for Research and Restoration, a department of the Museums of France. But in one of the portrait's layers of paint, Richardin's team also detected starch, an ingredient not previously found in any of Rembrandt's paints.

Curiosity piqued, Richardin and conservation scientist Jana Sanyova at the Belgian institute wanted to determine what kind of starch Rembrandt used. To collect more detailed chemical information, they turned to an up-and-coming technique in the art world, cluster time-of-flight secondary ion mass spectrometry (TOF-SIMS). The technique uses a high-energy beam of ion clusters to zap molecules off a surface and into a mass spectrometer. With high spatial resolution, cluster TOF-SIMS simultaneously maps both organic and inorganic molecules, something other techniques can't do.

Working on a tiny sample from the painting's dark background, the investigators confirmed the finding by the other analyses that the starch molecules were in the second ground layer, the layer in which an artist sketches the image before painting. Because TOF-SIMS allowed the researchers to observe the starch grains' shape and size, they could tell that the grains were wheat starch. The investigators will now focus on the Portrait of Agatha Bas, wife of Nicolaes van Bambeeck, also painted in 1641, to see if Rembrandt used this starch there as well.

The chemical mapping also allowed the investigators to find molecular interactions among paint ingredients that could affect the painting's integrity. For example, they discovered an interaction between linseed-oil binder lipids and lead white pigment, which could cause "lead soaps" to form and the paint to degrade, says Richardin.

Conservation scientist Narayan Khandekar at the Harvard Art Museums describes the work as "a big step forward" because it identified all the chemicals in a painting with high spatial resolution. Khandekar says artists such as the Old Masters experimented with pigments and binders in their paint to change the way it flowed from brush to canvas. Art historians previously didn't know that Rembrandt tried starch, probably in the form of flour, in his paint recipes. Khandekar speculates Rembrandt "was making a thicker, more viscous paint" but adds, "until someone actually mixes it up and tries it out, we won't know."

 
Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society

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