A little key to oxalate formation in oil paints: protective patina or chemical reactor?

By means of synchrotron based techniques, we propose an integrated mechanism for the degradation of 19 th century chrome yellow oil paints based on pigment reconstructions from historical recipes. We show that for certain paint formulations the darkening of these colours is triggered by the binder p...

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Bibliographic Details
Published in:Photochemical & photobiological sciences 2018, Vol.17 (3), p.266-270
Main Authors: Otero, V., Vilarigues, M., Carlyle, L., Cotte, M., De Nolf, W., Melo, M. J.
Format: Article
Language:English
Subjects:
Biochemistry
Biomaterials
Calcium
Calcium carbonate
Calcium oxalate
Chemical Sciences
Chemistry
Communication
Darkening
Electromagnetic absorption
Formulations
Kidney stones
Oxalic acid
Paints
Patina
Photodegradation
Physical Chemistry
Plant Sciences
Protective coatings
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Summary:By means of synchrotron based techniques, we propose an integrated mechanism for the degradation of 19 th century chrome yellow oil paints based on pigment reconstructions from historical recipes. We show that for certain paint formulations the darkening of these colours is triggered by the binder photodegradation which leads to the formation of calcium oxalate at the expense of the filler CaCO 3 , and the reduction of the chrome yellow pigment (Cr 6+ /Cr 3+ ). Considering that calcium oxalate is formed as a thin superficial layer, that may prevent light absorption by the paint bulk, we discuss its role as protective patina.
ISSN:1474-905X
1474-9092
DOI:10.1039/c7pp00307b