Comparative in Situ Study of Nanolime, Ethyl Silicate and Acrylic Resin for Consolidation of Wall Paintings with High Water and Salt Contents at the Chapter Hall of Chartres Cathedral

Abstract

ABSTRACT The consolidation of wall paintings is particularly challenging when high contents of water and hygroscopic salts have contaminated the masonry. Many wall paintings are in this situation, but only a few of them offer the possibility of easy access and long-term monitoring. The 14th century wall painting located on the east wall of the Chapter Hall of Chartres Cathedral (France) is one of these. The aim of this study was to assess the compatibility, efficacy and long-term behaviour of nanolime Calosil IP5, ethyl silicate Silres BS OH 100 and acrylic resin Primal E330S for the consolidation of such wall paintings. Observations and tests were performed before applications of products, then three, nine and fifteen months after. Temperature and relative humidity were monitored next to the tested areas during the whole period of the study. Nanolime did not improve the superficial cohesion of paintings, and whitish spots of lime appearing after application remain even after cleaning with cellulose poultice. Ethyl silicate did not show any measurable consolidating effect, but fifteen months after application it kept its initial hydrophobicity. A significant consolidating effect was achieved with the acrylic resin without considerable changes of water absorption and repellency, despite the appearance of some rare and scarce white spots.