A new non-destructive computational technique that measures the strength and condition of the canvas beneath great works of art could one day help museum curators determine if it is safe to loan rare pieces, according to art conservators.
A research team led by Dr. Marta Oriola of the University of Barcelona and Dr. Matija Strlic of University College London tested the new method on twelve Dali paintings. They found that the painted canvases were strong enough to travel to other museums.
Interestingly, their method also revealed that Dali used cheaper cotton canvases during his student days in Paris before later upgrading to linen. Previously, it would have been impossible to identify the canvas material without cutting out a piece to examine under the microscope.
To replace such damaging tests, the researchers needed to relate the results of traditional tests and their non-destructive technique.
The researchers first determined the level of degradation of the fibers, the acidity, and the material composition of about 200 small pieces of canvas cut from the edges of works painted around the same time as the Dali canvases.
Next, they measured another physical property of the canvas samples: how they interact with electromagnetic waves. A near-infrared spectrometer sent these waves through the canvas samples and recorded how much of the energy in the waves was absorbed by the canvas. Unlike the other measurements, the near-infrared spectrometer did not damage the canvas. Moreover, since it is a portable device that “looks like a small printer,” according to Strlic, the spectrometer can adapt to any size or shape of artwork.
Finally, the researchers built a mathematical model correlating the spectrometer data to the physical measurements. The model allowed them to determine the fabric type, acidity and strength of the twelve Dali canvases merely by matching minute-long spectrometer readings to the model’s predictions.
In addition to the twelve Dali works examined in the recently published article, the National Museum of Art of Catalonia has also already had 30 of their paintings measured, said Oriola.
However, the amount of preparatory work, cost and access to the instrumentation, prior conservation work, and satisfaction with current techniques pose challenges for the new method.
For example, designing a more widely applicable model would require physical measurements from many other canvases of different ages, since the current mathematical model was based only on early 20th century works.
Building a broader database might be hard, since the spectrometer costs €50,000 ($67,625), and while large museums have scientists on staff, “it’s not normal for an average conservator to do a lot of [this kind of] analysis,” said Kristin de Ghetaldi, a doctoral student of preservation studies, not affiliated with the study, who does chemical analysis of paintings.
Moreover, the researchers may have been lucky to find unmodified paintings, since “access to a collection by the same artist over a long period of time with fairly pristine artwork is unique,” noted Professor James Hamm, a paintings conservator also not involved in the work. He estimated that likely over half of the paintings in a museum might have the original back of the canvas obscured by an “Italian pasta lining” of starch, resin and glue.
Other conservation treatments, such as consolidation, when synthetic resin is added to a painting to strengthen canvas fibers, would also “spoil the ability to use the near-infrared system,” Hamm observed.
Additionally, the study found that subjective conservator assessments of canvas fragility matched well with the physical measurements, suggesting that visual examination of the canvas may be sufficient.
Still, Hamm thinks the research could be particularly valuable for looking at textiles, since “they’re not subject to a history of heavy treatment” in the same way that paintings have been.
De Ghetaldi agreed: “A cool place to take that would be to someone who has a textile collection that is fragile but also in demand and use the system as a way to protect the collection.”
The knowledge thus gained could cut both ways. Conservators who oppose transporting fragile works could use the new method to convince museum directors that the financial gain from loaning the works is not worth the risk of damaging the textiles in transit. “Nobody is going to argue with numbers or science,” de Ghetaldi said.