TECHNOLOGICAL ANSWERS
TO RESTORATION

The growing need to preserve our cultural heritage is causing a rise in the demand for increasingly accurate cleaning techniques, featuring high selectivity and low impact.

CASI DI STUDIO

WHITE MARBLE STATUE OF XVII CENTURY

Ordinary white marble statue of the seventeenth century depicting St. Anthony of Padua. AUTHORITY RESPONSIBLE OF THE RESTORATION: Academy of Fine Arts in Carrara RESTORER:  Elisa De Santi

AUTHORITY RESPONSIBLE OF THE RESTORATION: Academy of Fine Arts in Carrara

RESTORER:  Elisa De Santi

HISTORY:

the artwork is covered by a patina that through the interaction with biological deposits of fine particles led to the formation of thick deposits on which a new layer of dust is redeposited. The biological patina, formed by mosses and lichens mold, has strongly disintegrated and corroded the material, especially in the most exposed parts; moreover, in the basement, the  lichens incrustation were so deep  to infiltrate inside the stone itself.

LASER CLEANING METHODOLOGY

After a first wash with 30 grams of ammonium carbonate diluted in one liter of water, using brushes of medium and small size, we proceeded to clean with a micro-hydrosandblaster using aluminum oxide as an abrasive. The cleaning was performed on the left side of the artwork and then, given the good results obtained, it was extended to the entire surface. The black crust (close to the left side) was cleaned by laser (laser "Palladio" Nd: YAG, QUANTA SYSTEM spa with articulated arm) emission mode Q-SWITCHING, wavelength of 1064 nm with a pulse energy of 190 mj and pulse repetition rate of 10 hz.

The satisfactory results obtained allowed the extension of the laser cleaning to the whole black crust. The surface to be treated has been moistened with deionized water so as to create an optically darker surface, thus allowing a greater ablative effect . The laser was used on the surface with a pulse energy of 190 mj with a repetition rate of 10 Hz. At the back, after cleaning with the micro-hydrosandblaster, some incrustations were still present, and a drill was used to eliminate them. To fill the gaps, especially noticeable on the face and cracks, it was made a mixture consisting of:

- A part of hydrated lime;
- A piece of marble dust;
- A part of ACRIL 33 diluted in water to 20%.

After  the drying of the compound, the surface of the filler has been roughened so as to be more similar to the original degraded parts. Subsequently, in the integration, watercolor washes were performed with the addition of ACRIL 33 to allow attachment. The face was not reconstructed as evidence of the vandalism.
The finish consisted in the application of microcrystalline wax diluted with white spirit to 10%, applied with a soft bristle brush. After forty-eight hours the treatment was completed rubbing the surface with a soft nylon bristle brush. A consolidant was not applied as 
the artwork was going to be exhibited in the Church.