The procedure is remarkably successful

Feb 26, 2010 13:46 GMT  ·  By

Art restoration experts were recently surprised to learn just how efficient a laser-based cleaning method is to returning some vitality to tarnished wall paintings and other works of art. The method is derived directly from the techniques currently in use for tattoo removal, the scientists say, but they appear to work just as well for paintings. These old treasures are the latest addition to the list of objects that can be cleaned using a laser-based method, which also includes stone and metallic artifacts, the BBC News reports. At this point, the new technique is in use in Siena, Italy, at the Sagrestia Vecchia and the Cappella del Manto, in Santa Maria della Scala.

Scientists describe the progress made with lasers in the latest issue of the American Chemical Society's society journal ACS. The team that is performing the restoration operations is led by Applied Physics Institute-CNR expert Dr Salvatore Siano, from Florence, Italy. He and his collaborators have studied the effects of lasers on these sensitive and old materials thoroughly, so as to determine whether applying this technique carries with it significant side-effects. One of the most renowned artworks on which laser cleaning was used is the Renaissance-era bronze statue of David, sculpted by the famous Donatello. The “Gate of Paradise” bronze panels, belonging to Lorenzo Ghiberti, were also subjected to the same procedure.

In the second case, Siano says that significant progress has been made. “This was the first time a well recognized masterpiece was treated with laser cleaning,” he explained. The expert also revealed that, at this point, this cleaning method is being considered by many museums and private collectors around the world who want to have their prized possessions restored to at least a fraction of their former glory. “This is a more delicate situation than metals or stone as the pigment is much more fragile,” Siano also said. Using lasers for restoration purposes began being researched some 10 years before the first tattoo-removal devices became available, or before the first industrial paint-removal machines were set up.

In spite of the frailty many paintings display, their pigments endure laser light better than they do the corrosive and damaging chemicals that were until now used to clean them. A careful repair process no longer depends on a curator mixing the correct amount of each ingredient, which means that the end-result becomes a lot more predictable. With this, art owners can more accurately assess the risks they expose their possessions to. “Using chemicals means using something that can react all the time, even after one or two years. And if you compare it with mechanical means, the laser is able to distinguish what must be removed in a way that is much more selective than traditional techniques,” Siano says.

He explained that there were instances in which particular types of lasers needed to be used for specific paintings. However, those devices do not always exist in the real-world, so the team in charge of the repairs has to build a custom one, specifically for the job. The frequency and the duration of the pulses used are most of the times critical and determine the success or the failure of the entire cleaning operation. “The pulse duration is really crucial because it determines the time for the localized heating. Sometimes a long heating is harmful and sometimes a short heating is harmful,” the team leader further explained.