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| 100 |
1 |
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|a Van der Weerd, Jaap
|4 aut
|9 1072481
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| 245 |
1 |
0 |
|a FTIR Studies of the Effects of Pigments on the Aging of Oil
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| 520 |
3 |
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|a SUMMARIES. This study describes the changes in the infrared spectra of oil paint as a result of aging. The focus is on the influence of pigments on the long-term changes in the oil binding medium. Several naturally aged paints made with different pigments were analysed using Fourier-transform infrared spectroscopy (FTIR). One of the most pronounced effects observed in the infrared spectra of aging paint is the shifting and broadening of the carbonyl band due to the formation of carboxylic acids. Another effect of pigments on the oil binding medium is the catalysis of the hydrolysis of triglycerides, as indicated by the decreasing intensity of the ester absorption. Finally, the nature of the pigment included has a profound effect on the CH stretch absorptions. From these results it is clear that pigments can significantly alter the infrared spectra of drying oil, and should therefore be identified to ensure the correct assessment of the infrared spectra in drying oil paint.
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|a CONCLUSION. Several infrared spectra of traditionally prepared and naturally aged paints have been presented to investigate the long-term influence of the pigments on the oil medium. Reaction products of metal ions from pigments and the oil binding medium were found as metal carboxylates for a number of pigments. Other indications for reactions influenced by pigments were found in the aliphatic CH absorption at ~2930 cm-1 and the carbonyl absorption at ~1740 cm -1. The hypsochromic shift of the CH vibration is assigned to oxidation and ring closure reactions in the network part of the oil. These shifts are especially pronounced m paints pigmented by ochres, Naples yellow and ultramarine. The intensity of the ester peak at 1740 cm-1 can be greatly reduced by the presence of particular pigments, indicating hydrolysis of the triglycerides. This decreased intensity is especially clear for the zinc white and red lead paints, where the absorbance of the ester band is lower than the absorbance of the CH vibrations. Unfortunately, this relationship cannot be made fully quantitative, as the intensity of the CH vibrations is not a valid unit for the amount of oil material. Broadening and shifts of the carbonyl absorption have been observed in most of the aged paints. These effects are assigned to the formation of new, remarkably reproducible absorptions at 1707 +- 2 and 1780 +- 5 cm-1. The number of carboxylic acids, to which absorption at 1707 cm-1 is assigned, reduces upon the formation of metal carboxylates. This effect was observed for lead white, zinc white, red lead and Naples yellow. The characteristic carbonyl pattern is very useful in the investigation of oil paint, as it is normally not disturbed by any pigment absorptions.
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| 700 |
1 |
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|a Van Loon, Annelies
|4 aut
|9 770746
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| 700 |
1 |
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|a Boon, Jaap J.
|4 aut
|9 770719
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| 773 |
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|t Studies in Conservation
|d London: The International Institute for Conservation of Historic and Artistic Works, 2005
|g vol. 50, no. 1, p. 3-22
|x ISSN 0039-3630
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| 856 |
4 |
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|u http://www.viks.sk/chk/studcon_1_05_3_22.doc
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| 910 |
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|a memoriask
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