In situ characterisation of readhesion treatments for ceiling paintings using unilateral NMR

Ceiling and wall paintings pose significant challenges for historic house management due to their position at the interface between the environment and the building. Tight restrictions to modifications on built heritage prevent total control of the environment, resulting in temperature and humidity fluctuations. Different hygrothermal responses within the wall painting stratigraphy frequently lead to fracturing and lifting of paint layers, necessitating remedial conservation to readhere areas of detachment. Assessing the success of readhesion interventions is difficult due to the hidden nature of the treatment and, often, limited access. This paper presents comparative results of two different adhesive treatments employed during the conservation of the baroque ceiling painting in the Queen's Staircase at Hampton Court Palace, analysed with unilateral nuclear magnetic resonance (NMR). This non-invasive technique enabled monitoring of the adhesive systems, based on Jun Funori and BEVA^® 371 adhesives, up to a depth of 3,500 μm into the ceiling by providing specially resolved proton density profiles before and after treatment. The results offer a unique and pertinent assessment of treatment areas within a strictly limited timeframe. It is shown that the solvent carrier leaves the system within 24 hours and that the ultimate deposition of the adhesive can be identified.