Analysis of Watercolour Pigments Found in Thaddeus Haenke's Eighteenth Century Colour Chart and Attributed to Ferdinand Bauer

This paper describes the use of portable, in situ Raman spectroscopy, fibre optic reflectance spectroscopy (FORS) and XRF to identify watercolour pigments in an eighteenth century colour chart thought to have been created by the Austrian botanical painter Ferdinand Bauer. The chart is widely accepted to be the key to the unusual numbering system Bauer used in the field for the illustrations he made for the Flora Graeca, one of the most important printed books of the early nineteenth century. To date however, no pigment analysis has been carried out to firmly attribute the chart to Bauer. The results of the analysis demonstrated that good results could be obtained using a bespoke, portable Raman system using laser power densities low enough not to cause damage to the pigments, together with XRF and FORS. The data also showed that pigments found in the chart were similar to those used by Bauer in his paintings for the Flora Graeca adding weight to the attribution of the chart to Bauer.