South Tower Portal

Icon Laser Cleaning2. Laser Cleaning

Cleaning processes must not damage, and certainly must not destroy, original and valuable masonry surfaces.

For this reason, we have been using the ND:YAG laser technique to clean valuable stone objects for the last 15 years. (St. Stephen's Cathedral, Vienna; Minorite Church, Vienna; Bad Deutsch-Altenburg Basilica, Lower Austria; Carnuntum Archaeological Museum, Lower Austria; Palazzo Pubblico, Siena, etc.)

The devices are powered by an yttrium aluminium garnet (YAG) rod, which is a carrier of amorphous glass treated with neodymium (Nd.), a mineral that allows photons (light quantums) to be produced in the required wavelength (1064 nm = infrared). The key advantage of this technique is the short duration of its light pulses, at less than 10 ns (nanoseconds). Each pulse creates a shockwave in the layer of deposit and dirt. The micro-resonance causes the dirt to become dislodged without damaging the underlying stone because this reflects the beam.

The stripping properties can be adjusted precisely, which also means that it is possible to retain "patina layers" on the surface caused by age.

Projects

References