Oil Media on Paper: Investigating the Effect of Linseed Oils on Pure Cellulosic Paper Supports. A Research Matter of Damage Assessment

Abstract

Oil media on paper, such as oil paintings, sketches, prints, and books, occasionally present problems associated with the effect of oil medium on the paper support, raising a composite matter of condition assessment as it depends on several factors. The present work examines the effect of linseed oil on paper and, in particular, the changes caused by three types of linseed oil on the optical, morphological, mechanical, and chemical properties of pure cellulosic paper, employing mock-ups submitted to artificial ageing in controlled conditions of relative humidity and temperature in airtight vessels. The study involved colorimetry, opacity, tensile strength, pH measurements, SEM, FTIR, and VOC analysis with GC-MS. Processing of the results has so far indicated that thermal-humid ageing caused the gradual darkening of the oil-impregnated mock-ups, as well as alterations in opacity, intense fall of pH values, and severe reductions in tensile strength, while linseed oil processing during manufacture has a significant impact. FTIR spectra have indicated that chemical changes upon ageing are in accordance with those of optical and mechanical changes, while VOC emissions are mostly associated with the drying and degradation of the different types of linseed oil.

Oil Media on Paper: Investigating the Effect of Linseed Oils on Lignocellulosic Paper Supports

“…A small number of research works on this matter have published in the past, though they do not provide adequate results to compensate to the interpretation of alterations and problems recorded in original works [7][8][9][10]. Recently, the authors of the present work reported the initial results of an investigation into the effect of linseed oils on pure cellulosic paper [11]. Specifically, we have researched the changes in the optical, morphological, mechanical, and chemical properties of pure cellulosic paper mock-ups impregnated with three types of linseed oil, subjected to thermal-humid ageing in air-tight vessels.…”

“…The research followed the exact methodology applied to the investigation on pure cellulosic paper supports reported in previous work carried out by the authors of this work [11]. Experimental work included colorimetry, opacity, tensile strength, pH measurements, SEM, FTIR, and VOC analysis with GC-MS.…”

“…Oil-impregnated mock-ups were air-dried at room conditions of 22 • C and 52% RH for 40 days, hanged in racks using pure cotton threads. Mock-ups were prepared and subjected to accelarated ageing in air-tight vessels in conditions of 77% relative humidity and 80 • temperature, the same used for pure cellulosic papers [11].…”

“…In addition, they appeared to be lighter than the other two sets at all stages of ageing, while the mock-ups impregnated with refined linseed oil (M + RF) were darker than those impregnated with cold-pressed linseed oil (M + CP). This observation also applied to the white cotton mock-ups [11]. Oil treatment during manufacture could cause differences in yellowing and darkening upon ageing [17].…”

“…It could be suggested that changes in the opacity of the mock-ups can be mainly attributed to linseed oil formulations and their different properties. Taking into consideration the changes in opacity on the oil-impregnated mock-ups of cotton [11], which has similar weight to Kraft, results show that oil-impregnated Kraft mock-ups are less opaque, indicating differences in linseed oil's penetration into the paper pulp. This also confirms the observations in color changes (Section 3.1).…”