Oil media on paper: reflections on condition assessment in a new context

Works created with oil media on paper present problems associated with the absorption
and diffusion of oil mediums or oil binders into the support. This paper elaborates on recent results of
research on the effect of oil mediums on paper supports, the factors that influence the extent of damage,
and the indications that determine the condition of the works. Research results on the changes of the
optical, morphological, mechanical and chemical properties of paper caused by oil binders are based
on experimental work on mock-ups submitted to artificial ageing, in controlled conditions of relative
humidity and temperature in airtight vessels. Three representative types of paper impregnated with three
types of linseed oil, typically used for oil painting and printing, were selected for the preparation of the
mock-ups. The outcome of colorimetry, opacity, tensile strength and pH measurements in correlation
with the results obtained by SEM and FTIR analysis contributed to the scientific explanation of the
changes in colour, opacity, pH and mechanical strength of the paper support, reported by conservators
in original works. The conducted research could form the basis for the formulation of a useful ‘tool’ for
condition rating involving a recommended methodology of study.