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

SANDSTONE CAPITAL

SANDSTONE CAPITAL FROM THE XIII CENTURY (25 X 20 X 20 CM)

 

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

RESTORER:  Elisa De Santi

HISTORY: Under a first powderlike deposit, the surface of the head appeared covered with deposits of atmospheric particles and a thick black crust.

These deposits, anchored firmly to the surface tended to desquamation in sheets and flakes, because in some parts of the work some gaps and loss of material were present.

Underneath the black crust, of variable thickness, the surface appeared powder-like.

 

LASER CLEANING METHODOLOGY

Preliminary cleaning trials were initially performed on a sample. The surface appeared detached and therefore  a normal mechanical cleaning with scalpels, not practicable without a previous consolidation, would have caused the removal of parts of the original material compromising the status of the work.

The cleaning trials were performed with a  "Palladium" laser by Quanta System, in Q-switching mode with a pulse energy of 190mj and a repetition frequency of 10 Hz.

The desired uniform cleaning was obtained.
The very satisfactory result of sampling allowed to undertake the complete restoration. Initially the artwork was subjected to the removal of dust by soft brushes.
Subsequently, the surface to be treated has been moistened with deionized water, so as to optically create a darker surface, thus allowing a greater ablative effect.
The laser was used on the surface with a pulse energy of 190mj with a repetition frequency of 10 Hz as for the sample.
In some points, where the thickness of the incrustations was greater, the pulse energy used was 200 mJ with a repetition rate of 10 Hz
The cleaning was repeated several times by tilting the handpiece where the parts to be cleaned were difficult to achieve.

The use of laser was always very controlled and calibrated in the operational parameters of . The action of the laser on the surface was often stopped to check  the effect achieved while preserving the original patina.
After the cleaning was completed, to consolidate the detached parts and cracks injections with Paraloid B72 were carried out; 20 g of this acrylic resin were diluted in 250 ml of Nitro. Subsequently the cracks have been filled with a part of sandstone powder and a part of Lafarge white lime, mixed in water.
To obtain a coloration more consistent with the altered stone (due to the presence of iron oxides within sandstone) pigments were added to the mixture.
At the end of this operation, natural earths mixed with water were applied by brush on fillings to achieve greater uniformity in the coloration.