The development and application of chromatographic techniques in the characterisation of artists' media

The aim of this project was the development and application of chromatographic techniques for the characterisation of proteinaceous and natural gum materials used as binders, adhesives et cetera by artists. Proteinaceous materials (animal glue, casein and egg proteins) were hydrolysed under acid conditions prior to derivatisation with 9-fluorenylmethyl chloroformate: the amino acid content of the samples was then determined by reverse phase high performance liquid chromatography. Sixteen amino acids were monitored, their relative percentages providing a means of differentiating between the proteinaceous media types. Natural gum materials were silylated with hexamethyldisilazane after acid hydrolysis, then their sugar components were separated and identified by gas chromatography-mass spectrometry, using selected ion monitoring for maximum sensitivity. A sugar composition 'fingerprint' was obtained for each standard gum material analysed, facilitating the characterisation of gum media from works of art. Samples of suspected proteinaceous and gum media were removed from works of art from the Tate Gallery's collection, focusing on 18th and 19th century British works, particularly those of William Blake, J. M. W. Turner and Dante Gabriel Rossetti. The characterisation of media samples from such works provided valuable information regarding the nature of media preferred by artists of this period, additives to gum media and, perhaps most importantly, the relationship between binding media and support and their effects on the condition of ageing paintings