Laser Precision

April 1, 2016
Index Magazine

Laser Precision

Picture an individual who uses lasers as part of her job, and you might imagine a radiologist, a surgeon, maybe even a tattoo-removal specialist. One role you may not expect is art conservator.

However, at the Straus Center for Conservation and Technical Studies, as at many conservation labs, a laser is indeed an essential tool of the trade. (Read about other key pieces of Straus Center equipment we’ve highlighted: the MALDI and the FTIR.)

“We don’t use the laser all that often, but when we do, it’s just so amazing,” said Susan Costello, associate conservator of objects and sculpture. “It can remove grime very evenly and quickly.”

Originally developed for the medical industry, lasers have been employed in some art conservation labs since the 1970s. The Straus Center has had its laser—officially called a 1064nm Nd:YAG (neodymium-doped yttrium aluminum garnet)—for many years. As laser technology and its usefulness develop, more labs are incorporating different types of the device into their toolkit.

Immediate Results

The Straus Center’s laser has a single wavelength. Its energy “interacts very strongly with some materials, but hardly at all with others,” Costello said. This selectivity allows conservators to use the laser to clean certain hard surfaces, such as marble, without damaging the object itself. “The energy from the laser beam is strongly absorbed by the dirt, which is ejected from the surface,” Costello said.

As soon as dirt is removed—within nanoseconds—the laser energy is reflected away from the object. There’s no cleanup to speak of; an exhaust hood over the area sucks up the vapors produced. This protects the conservator from any harmful inhalations (in some cases, the conservator will wear a dust mask to guard against flying particles as well). The results of the treatment are apparent right away—though the grimier an object, the longer it takes to fully clean.

Best Tool for the Job

Costello recently used the laser to clean a 17th-century architectural railing from Delhi, India, in preparation for a loan to the Cleveland Museum of Art. Carved of marble in an intricate floral, open-work pattern, the railing may well be the finest of its kind in North American collections. In Cleveland’s exhibition this summer, it will help illustrate a cultural shift that took place during the 17th century, when Mughal rulers claimed an elevated form of sovereignty and introduced white marble into palace spaces. (Previously, white marble was reserved for religious architecture; buildings occupied by living emperors were made with red sandstone.)

Mary McWilliams, the Norma Jean Calderwood Curator of Islamic and Later Indian Art, consulted with Costello to determine whether the laser’s use would be appropriate in the case of the marble railing, which appeared darkened from grime, pollution, and biological matter. Other cleaning methods tested and considered were chemical solvents and steam. However, “in this case,” Costello said, “the laser was the only way to remove the grime from the railing but leave its patina intact.”

A Steady Hand

Just a few Straus Center conservators are trained to use the tool. Costello said even seemingly minor skills—such as adjusting the laser’s energy level—are actually critical. “It takes a lot of training and experience with art objects to be comfortable with the laser and to use it safely,” she said.