The role of water in the restoration of paintings

Abstract

Cleaning old paintings has always been a major problem, because aqueous solutions may dissolve pigments. We succeeded in cleaning some precious old paintings of Siena using aqueous products. This success encour- ages us to clean a Lorenzetti masterpiece in the near future. The techniques used and a possible explanation of the surprising result are discussed in the light of recent insights into the physics of water. In the present paper we discuss the cleaning of some old paintings of the Pinacoteca Nazionale of Siena (Museum of Sienese Paintings). The present study is part of the project 'Ricerca Applicata alle Pellicole Pittoriche delle Opere Policrome della Pinacoteca Nazionale di Siena', carried out in col- laboration with Siena University and the Superintendent of Historical, Artistic and Ethnoanthropological Heritage of the Provinces of Siena and Grosseto (National Art Gallery), financed by the Monte dei Paschi (MPS) Foundation (2006-2008), having the objective of interdis- ciplinary study of recent noninvasive methods of cleaning surfaces painted with protein-based materials. An advantage of these methods is their low toxicity for restorers. The first work cleaned was a tempera on wood attributed to Niccolo di Buonaccorso (Fig. 1). It is an altar piece, probably made for private use, measuring 110 × 75 cm and depicting scenes from the New Testament around a central crucifixion. It is crowned by a lozenge showing the Assumption of the Virgin Mary, and completed by a false predella depicting various saints (1-4). The painting was restored in the 1930s and the painted surface was in good condition, except for sporadic areas of colour sealed with beeswax. The support was also in good condition, except for a crack running the whole length on the left side. Near the main gaps in the surface and the gilt frame, there were many touch ups and patches of false gold (porporina).