Marie-Claude Corbeil

X-ray powder diffraction data for selected metal soaps

In order to better characterize metal soaps found in paint films or on metal surfaces, several metal soaps were synthesised and their x-ray powder diffraction patterns measured. Metal soaps were obtained from four different fatty acids found in drying oils, two saturated (palmitic and stearic acids) and two unsaturated (oleic and linoleic acids), and from copper, zinc, and lead, three metals that are typically found in metal alloys and paint systems. X-ray powder diffraction data are reported for the following compounds: palmitic acid, stearic acid, zinc palmitate, zinc stearate, zinc oleate, zinc linoleate, copper palmitate, copper stearate, copper oleate, lead palmitate, lead stearate, and lead oleate. Features that are characteristic of specific compounds were observed. Soaps obtained from different fatty acids with the same metal ion show differences, as do soaps obtained with the same fatty acid but with different metal ions. Differences were observed when x-ray powder diffraction data obtained for stearic acid and zinc stearate were compared to published data for these two compounds (PDF 38-1923 and 5-0079, respectively). In the case of stearic acid, differences could be explained by the fact that the specimen reported previously in PDF 38-1923 was likely contaminated with palmitic acid. In the case of zinc stearate, low angle data were missing from the original patter PDF 5-0079 and peaks that were reported in other angular regions in fact consisted in more peaks that were not resolved due to broadening.

Conservation Issues in Several Twentieth-Century Canadian Oil Paintings: The Role of Zinc Carboxylate Reaction Products

In an on-going study of the materials and techniques of twentieth-century Canadian painters, similar conservation issues in oil paintings by various artists have been noted. These include delamination and lifting paint, zinc soap protrusions and surface efflorescence or accretions. Examples of these phenomena are presented. Delamination in an oil painting from 1956 was found to be related to an underlayer with a high concentration of zinc fatty acid salts (zinc soaps). In two paintings that date from 1936 and 1937, zinc soaps have aggregated and formed protrusions that have broken through the paint surface. The protrusions were analysed using a combination of SEM-EDX, GCMS and FTIR. The FTIR spectra were compared to those of synthetic zinc palmitate, stearate, azelate and oleate. The combined GCMS and FTIR results indicate that the protrusions contain primarily zinc palmitate and stearate. Peak splitting in the FTIR spectrum, which is not observed in synthetic zinc palmitate, stearate or binary palmitate-stearate salts, is likely due to structural distortion. The final example describes a disfiguring surface accretion on a 1952–1954 painting caused by the reaction of zinc with a low molecular weight carboxylic acid (2-hydroxypropanoic or lactic acid).

Conservation institutions as agents of change

Key messages to conservation institutions were drafted during the ICCROM Forum 2013 on Conservation Science so they could, in turn, influence the profession. The first message is a general statement of the fact that conservation science is an essential part of conservation. The other messages provide guidance to conservation institutions so that they can achieve maximum impact. Conservation institutions should engage in research and development that anticipate issues, provide sustainable solutions and guidelines, and are conducted in a transdisciplinary way; share resources and expertise to be more efficient, increase access and reduce inequalities; and assume a leadership role, promote conservation, and ensure knowledge is made available. The key messages, five altogether, are reproduced in their entirety in this article, which provides further elaboration and development of each message as well as avenues for making positive changes in strategic areas.