Photochemical colour change for traditional watercolour pigments in low oxygen levels. (January 2015)

• Record Type: Journal Article
• Authors: Lerwill, Andrew; Townsend, Joyce H.; Thomas, Jacob; Hackney, Stephen; Caspers, Charlotte; Liang, Haida
• Is Part Of: Studies in conservation. Volume 60:Number 1(2015)
• Page Start: 15
• Page End: 32
• Publication Date: 2015-01
• Subjects: Art objects -- Conservation and restoration -- Periodicals; 700.288
• DOI: 10.1179/2047058413Y.0000000108
• Languages: English
• ISSNs: 0039-3630

Abstract

<abstract> <title> <x content-type="archive" xml:space="preserve">Abstract</x> </title> <p>An investigation for light exposure on pigments in low-oxygen environments (in the range 0–5% oxygen) was conducted using a purpose-built automated microfadometer for a large sample set including multiple samples of traditional watercolour pigments from nineteenth-century and twentieth-century sources, selected for concerns over their stability in anoxia. The pigments were prepared for usage in watercolour painting: ground and mixed in gum Arabic and applied to historically accurate gelatine glue-sized cotton and linen-based papers. Anoxia benefited many colorants and no colorant fared worse in anoxia than in air, with the exception of Prussian blue and Prussian green (which contains Prussian blue). A Prussian blue sampled from the studio materials of J.M.W. Turner (1775 − 1851) was microfaded in different environments (normal air (20.9% oxygen) 0, 1, 2, 3.5, or 5% oxygen in nitrogen) and the subsequent dark behaviour was measured. The behaviour of the sample (in normal air, anoxia, and 5% oxygen in nitrogen) proved to be consistent with the 55 separately sourced Prussian blue samples. When exposed to light in 5% oxygen in nitrogen, Prussian blue demonstrated the same light stability as in air (at approximately 21°C and 1 atmosphere). Storage in 5% oxygen is proposed for 'anoxic' display of paper-based artworks that might contain Prussian blue, to protect this material while reducing light-induced damage to other components of a watercolour, including organic colorants and the paper support.</p> </abstract>