Yellow organic dyes in the 19th century paints of Jan Matejko. Identification of dyestuffs, carriers and fillers

Abstract

Natural organic dyes can be found in many objects of cultural heritage. Identification of coloring substances present in historical paints provides relevant information for a wide range of specialists involved in art science. Determination of the composition of paints allows application of appropriate procedures for restoration and conservation of historical works of art. This information enables treatment in accordance with the ideological and esthetic decisions of the authors. The complexity of the chemical composition of art paints, which, apart from organic dyes can also include inorganic pigments, binders and other additives, hinders isolation and identification of its individual components. Nowadays, there are several analytical techniques and methods for extraction and identification of organic dyes, each of them has its limitations, however. For that reason, the development of the universal methodology for the analysis of colorant composition in art paints remains a challenge for chemists. In present work, an analytical protocol for identification of yellow dyes using reversed phase liquid chromatographymass spectrometry with atmospheric pressure electrospray ionization (LC-ESI/ /MS) is presented. The developed method was successfully applied to identification of the main components of Indian Yellow, weld (Reseda luteola L.), buckthorn berries (Rhamnus) and madder lake (madder plant’s root) extracts, in the historical oil paints from tubes of Richard Ainès company, formerly Mulard, owned before him by recognizable French art materials supplier Eduard. The recognition of paints composition was broadened by identification of non organic compounds – carriers of the dye: aluminum hydroxide, tin chloride, chalk, as well as filler like silica and or lead white. Researched samples of painting materials belonged to 19th century famous Polish painter Jan Matejko (1839–1893) and will be very helpful in understanding paintings of him and of his contemporaries.