In the innovative "open laboratory", created in the "Cortile delle Zitella" of the Vatican Museums, the restoration of preparatory models of the bronze figures of the Angels and Saints created by Bernini for the Cathedra and the Blessed Sacrament Chapel in St. Peter's Basilica is now underway. The restoration, financed by the New York Chapter of the Patrons of the Arts in the Vatican Museums, is being carried out by specialists in the Laboratory of Ceramics and Metals of the Vatican Museums, under the direction of the Director, Professor Antonio Paolucci. The supervision of the conservation procedure is entrusted to Professor Arnold Nesselrath, Chairman of the Scientific Board of the Vatican Museums. These works of art, together with the heads of Saint Athanasius and Saint John Chrysostom, are conserved in Room XVII of the Vatican Museums' Pinacoteca. These models may be dated back to between 1661 and 1673.

Courtesy of the Fabbrica di San Pietro in the Vatican

These models are of unique value, not only because of their artistic quality, but also as they reveal the method used by Bernini during the creative process. The sculptures are made of a mix of clay and straw, modelled around a framework of iron rods and fixed to a vertical wooden support. "Looking closely at these models in raw clay" - observes the Director of the Vatican Museums, Professor Antonio Paolucci, - "we discover the creative virtuosity, the spiritual transfiguration of matter, soft to the fingers, of an artist whose dream was to sculpt the city as if it was one immense sculpture".
The models of the Angels, now undergoing restoration, testify to Bernini's enormous commitment - underlines Dr. Alessandra Rodolfo of the Vatican Museums Arts Department - in creating the grand monument of the Altar for the Cathedra in St. Peter's Basilica (1658 - 1666). It took the artist more than ten years to complete the work, which he modified several times during the course of the years. In fact, the differing dimensions of the Angels attest to two different stages during their creation, as adjustments were made as the work progressed, in that the first version seemed too small compared with the proportions of the whole structure.

The peculiarity of the material used to create the works of art, and the lack of records about previous restorations performed on similar material, necessitate in-depth research, so as to establish the appropriate intervention to be used during the restoration process. Since the clay was not subject to firing, it is now extremely fragile to thermo-hygrometric variations. The presence of vegetable fibers inside the clay mix as well as those used for reinforcement, as can be seen in the arm, where vines were tied together with twine and wrapped around the iron rods, constitute an extremely fragile material that is easily degraded by biological agents (xilofag insects). For these reasons the conservation process is carried out, so as to ensure that all the materials used to create these works of art are guaranteed the maximum chemical and physical stability, by using instruments and substances which are compatible with these materials.

        

Flanking the research on Bernini's technique, a scientific study is carried out, since the surface still retains traces of the precious fingerprints of the great artist as he worked the clay as well as marks left on the instruments used by him.
During the preparatory stage, the restorers, in collaboration with the Scientific Research Laboratory of the Vatican Museums, studied and analysed the effects of the different substances to be used during the restoration on analogous material (clay and organic components). Part of the restoration process includes the removal of material used during previous restorations, revealing methods and materials, such as plaster and coloured substances, considered inappropriate and invasive nowadays. This type of intervention is essential so as to restore the original surfaces, as well as ensuring the preservation through time of the works of art, freed from harmful substances that accelerate their deterioration.

Different kinds of material were used to create the models, which differ according to their function: the clay mix and the internal and external framework. The material used to sculpt the Angels is composed of a mix of clay and dry grass, applied in layers, varying in thicknesses and composition, so as to avoid the creation of cracks whilst the clay is drying.

        

The several layers of clay are heavy and therefore are in need of internal and external frameworks which are made up wrought iron, wire, organic material, such as vines tied together with twine, and numerous wooden elements. The areas which are lacking the outer finishing clay layer are extremely fragile and present multiple cracks and fissures. These surfaces enable one to study the different layers as they reveal the method used by Bernini during the creative process.

During recent decades, the clay and dry grass models created by Gian Lorenzo Bernini have undergone other restoration interventions, considered inappropriate nowadays. The initial surveys, mapping and removal of dust from the surface have brought to light these previous interventions. Numerous in-filling and reconstruction of missing parts, in white plaster painted so as to have the same clay colour tone, came to light straight away. Particularly noticeable was the use of a coloured substance covering the original surface, which has in time turned yellow.

      

The insertion of metal nails used to reinforce the different parts was also evident. In correspondence with the undercuts of the model, particular dust and biological deposits have accumulated, proving that the organic components of the work of art, such as the wood and straw, have been damaged by insects. The surface of the clay that has been sculpted presents numerous fissures, which in part may be attributed to the natural behaviour of the clay mixed with straw, and to shrinkage whilst drying.

The first step in the restoration process consists in closely examining the surface through a magnifying glass, while it is being cleaned via micro-suction so as to remove the film of dust that had accumulated over the surface. The accumulated dirt, which through time has turned the surface grey, is removed by using rubbers of varying compositions and consistencies, developed for the delicate restoration of paper. Paint and other substances are removed by using solvent compresses which do not leave any residues or unctuousness on the clay surface. The numerous fillings and reconstruction of missing parts, in white plaster, now cracked and detached, are extracted mechanically by using a dental micro drill mounted with specific heads used for plaster.

      

The corroded wrought iron elements of the framework are cleaned mechanically so as to remove metallic elements that cause damage. Afterwards the metal parts are treated with substances that delay any form of deterioration. With regard to the consolidation and to the integration of the missing parts, a cellulose-based mix is used, formulated specifically for the restoration of these works of art. This material, which is light and grease-free, easy to use and to remove, is applied with the aid of dental instruments so as to carry out micro stuccoing. Areas which show greater breaking-up are consolidated via the injection or the brushing-on of adhesive and consolidating substances. The structures supporting the weaker areas of the work of art are secured by building-up structural integration with the stronger areas, using a mix studied expressly for the purpose. The smaller stuccoing and integrated areas are rounded off slightly beneath the level of the original surface and finished off with an aquarelle colouring, applied by using the puntinato technique which respects the need to recognise the parts which are not original.