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

WOODEN CRUCIFIX

THE RESTORATION OF THE WOODEN CROSS OF ST MARY OF THE SOUL AND THE RE-DISCOVERY THE ORIGINAL POLYCHROMY

The restoration of the wooden crucifix in the church of Santa Maria of the Soul in Rome l was carried out on site, avoiding the removal of the work from its current location, not to alter the delicate balance of the anchorage system to the wall behind it.
The sculpture, made by Giovanni Battista Montano in 1584 for the Church of Santa Maria of the Soul, was in a very compromised conservation state, evidenced by an abnormal “bubble-like” lifting  of the paint film. The damage, caused probably by the proximity to a source of abnormal heat, resulted in the formation of bubbles concentrated along the vertical axis, some of which, for the progressive loss of adhesion of the layers of the preparation below, have imploded, assuming the appearance of micro craters.

The microscopic observation of the margins of these small cavities, supported later by stratigraphic investigations, showed the presence of an original polychromy below the thick bituminous patina which  made the wooden sculpture look like bronze. This patina is difficult to date and is probably related to a change in taste. From a stratigraphic point of view it is contemporary to the last gilding of the  loincloth.
After the removal of incoherent deposits and a preventive disinfestation, a series of cleaning tests were performed with the aid of solvent mixtures. These have shown the presence of three layers of bituminous paint superimposed to a pinkish repainting, lying on the original paint layer. Only following the results of these tests it was decided to use a laser, which has represented a valid alternative to the traditional techniques. In fact, the liftings, softening in contact with solvents, threatened to break.

LASER CLEANING METHOD:

Laser cleaning allowed the removal of the unwanted layers while ensuring the integrity of the original surface. With the use of the laser beam it was possible to follow all irregularities of the surface, allowing the achievement of a uniform level of cleaning even in the most inaccessible and delicate areas, thanks also to the proper choice of the pulse length and frequency. The devices used were, in a first step, the laser prototype EOS Vario and subsequently the laser Eos 1000 LQS. The unconventional pulse duration (100 ns) was fundamental to optimize the result. A longer pulse would have resulted in thermal hazards to the original pigment, too short pulses(QS) would have compromised the fragility of the paint film. Subsequently, the consolidation of the liftings of the paint film was obtained by infiltration of microacrylic emulsion and the gradients of the surface reduced through the use of small rollers so as to ac-commodate the irregularities of the surface. The fillings of the gaps have been performed with the use of plaster of Bologna and rabbit skin glue and then repainted with watercolors.

ADOPTED SYSTEM