A laser is a unique source of energy, providing an intense, highly directional, pure form of light that is able to deliver energy to a surface in a highly controllable manner. The most commonly used laser cleaning systems in conservation emit very short pulses of infrared light, typically at a wavelength of 1064 nm. Light at this wavelength tends to be absorbed strongly by pollution encrustations and many other types of dirt layers and surface contaminants, whereas the surface of the artwork often reflects this light strongly; to some extent the laser beam is able to differentiate between the dirty and clean surfaces.
The energy absorbed by the dirt layer is almost instantaneously converted into heat; this extremely fast heating effect generates forces sufficiently strong to eject the dirt particles away from the surface. In many cases, the light interacts only weakly with the surface of the artwork and the removal process stops as soon as the clean surface is exposed.
The control offered by laser cleaning enables the conservator to remove unwanted layers without overcleaning the valuable surface of the artwork; patina, fine surface detail, tool markings and important surface coatings can be preserved. Laser cleaning systems provide the conservator with an extremely gentle method of cleaning which can be used to remove dirt from very fragile surfaces; from a badly weathered marble surface in need of consolidation or from the delicate petals of a rose, as seen in the video clip above.