Treatment of a nineteenth century male portrait in oil including the characterisation of materials, technique and a study of the lead soap aggregation in the paint composite

Dissertação para obtenção do Grau de Mestre em Conservação e RestauroThis project involved the conservation of a 19th century portrait in oils from the Ecomuseu do Seixal (Portugal). The painting of “João Luiz Lourenço” was in very poor condition. Because of the range and severity of the problems presented, it offered an opportunity to explore important aspects of painting conservation in-depth. The approach to its treatment required an empirical investigation of a number of materials and techniques used in the field of conservation/restoration. Of additional interest, the painting exhibits widespread evidence of metal soap (lead carboxylate) aggregates protruding through the paint from the ground layer. The painting’s materials and the metal soaps aggregates were studied and characterised with different analytical techniques: μ-EDXRF (Energy Dispersive X-ray Fluorescence), μ-Raman Spectroscopy, μ-FTIR (Fourier Transform Infrared Spectroscopy) and SEM-EDX (Electron Scanning Microscopy with Energy Dispersive X-ray Spectroscopy). Part 1: describes the study of the materials and the technique of the painting, and of the metal-soap aggregation within the painting’s ground layer. Observation with the Optical Microscope and with SEM-EDX of paint/ground cross-sections reveals the presence of two visually distinct lead carboxylate aggregates: one, completely white, and the other with a white centre surrounded by distinct red particles identified as red lead (minium: Pb3O4) by μ-Raman. The presence of these two types raises questions about whether there are different starting materials for the aggregates or whether they could be in different states of evolution. Part 2: describes the design and implementation of the conservation/restoration treatment. The treatment of the painting raised challenges and at various stages involved the exploration of non-traditional methods. At every stage during the treatment the consequences of an intervention was carefully considered in relation to the subsequent steps. All decisions were taken according to the painting’s intrinsic conservation problems and materials and with regard to the future environment of the painting