VACUUM TECHNIQUE FOR RESTORATION
2. APPLICATION OF STRIP LINING ON A PAINTING ON CANVAS BY O. PORTA USING THE VACUUM TECHNIQUE AND EQUIPMENT THAT REPLACES THE HOT TABLE.
The painting (300 x 180 cm) is from the Church of St. Francis, Foiano della Chiana (Arezzo).
The canvas support is divided into five pieces held together by four horizontal seams. The ground layer is gesso and glue and the paint film is very thin.
The original stretcher lacked the base bar and one cross bar, and was disconnected, distorted and infested by xylophagous insects. Therefore, it was replaced by a new expandable and well-dimensioned stretcher.
The canvas support was very deformed with folds and vast paint losses concentrated in the lower part of the painting.
Despite the serious preservation status, we chose not to line the painting with the traditional system of glue-paste, because of the many seams, which with this lining method would have had to be thinned by an invasive and irreversible intervention, and because of the sensitivity of the painting to the moisture of the glue-paste adhesive.
We decided to apply strip lining of synthetic canvas joined with Beva film (a thermoplastic synthetic adhesive) under vacuum and at controlled temperature with an apparatus developed by our Studio for localized heat application. This apparatus replaces the hot table; in fact, this large painting could not have fit in normal commercial hot tables.
Moreover, using a hot table to join the strips would have meant heating the whole surface of the painting, exposing the paint layers to useless stress since the temperature of activation of the consolidant is around 65-70°C. However, before applying the strip lining, we consolidated the paint film under vacuum with Plexisol P550.
The results were very satisfactory: the work was consolidated and attained perfect planarity, without unpleasant side effects caused by vacuum pressure, such as crushed impasto; it must also be considered that the painting was not protected in the phase of paint film consolidation or during application of the strip lining. These results were due to particular care in preparing the vacuum, at low pressure (-10 kPa, around 10% of total vacuum) distributed gradually and uniformly over the entire surface, and perfect temperature control (±0.5°C) with out computerized unit.
