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[CICRP - Interregional Centre for Heritage Conservation and Restoration]
Characterisation and accelerated ageing assessment of two twentieth century blue paints
Authors : Alain Colombini, Jean-Marc Vallet and S. Hourany (engineer student, Université de technologie de Compiègne)
Poster presented at the 5th E.C. Conference of Cultural Heritage Research in Krakow (Poland) in 2002.
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Abstract :
Condition reports done on some twentieth century paints have shown some premature degradation. In order to understand the occurred phenomena, two types of blue pigments, most commonly used by contemporary artists have been studied.
Accelerated ageing tests were carried out on samples made out of cobalt blue P.B.28 (inorganic pigment) and phtalocyanine blue P.B.15 (organic pigment) in paint binding media such as popyseed oil, acrylic, alkyd, vinyl-vinyl versatate, and acrylic-vinyl.
The behaviour of materials have been characterised by means of F.T.I.R., X.R.D. and colour measurement. Results obtained by F.T.I.R. have showed the limits of this technique when comparisons are made between the binding media. X-Ray Diffraction is mainly used for the inorganic pigments and the extenders. Accelerated ageing tests and colour measurement have displayed some significant changes.
Both alkyd and oil paint seem to be the most sensitive to “yellowing” and hydrolysis degradation while acrylic-vinyl paint on the whole showed best results in term of colour and chemical change.
The presence of hydroxy in the tests after the ageing period is most significant. On the other hand commercial paints did not display any hydroxy increase.
The pigments chosen in this study are very resistant. Binders are subject to alterations.
An example of twentieth century paint analysis was studied. The binding medium is characterised while the pigment is not identified. Some hydrolysis degradation is suspected.
Page mise à jour le 11 octobre 2007.
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