Cleaning of oil-on-stone wall paintings : lessons learned from easel painting conservation

Abstract

The development of a treatment for a seventeenth-century CE wall painting scheme in Valletta, Malta, highlights the particular challenges of cleaning oil-based wall paintings. Materials selection and intervention design took into consideration the composition of original paint- ing materials and their degradation processes, including ageing of the oil binder, pigment alteration and metal soap formation. Emphasis was placed on the evaluation of cleaning results, beyond their aesthetic impact. This study also draws attention to the overlap between the fields of easel and wall painting conserva- tion. While much research has been conducted into the deterioration and treatment of oil-based easel paintings, comparatively little similar work has been done for oil- based wall paintings, where such deterioration is present and possibly even more common, due to the generally inseparable link between wall paintings, their architectural substrates and their in situ environment.