FROM BECKMANN TO BASELITZ – TOWARDS AN IMPROVED MICRO-IDENTIFICATION OF ORGANIC PIGMENTS IN PAINTINGS OF 20th CENTURY ART

Today, synthetic organic pigments play a major role as colorantsof excellent light-fastness in artists' paints. Theiranalytical determination in paintings gains steady importancewith respect to attribution and studio practice of certainartists as well as dating and authentication. Syntheticorganic pigments have extremely varied chemical structuresand properties such as colouring strength, solubilityor thermal stability. Therefore, it is a challenging task tofully identify all organic as well as inorganic colorants andfillers in a micro-sample taken from a painting. A complementarysampling and analytical approach is suggested,that combines micro-chemical and solubility tests, Ramanmicroscopy, pyrolysis gas chromatography/mass spectrometry,thin layer chromatography and/or high-performanceliquid chromatography on a case-to-case basis. This paperpresents results and discusses practical experiences withRaman microscopy as a rapid and minimally invasive techniquefor the identification of organic pigments in paintsamples. Case studies from 20th century German artworksby Max Beckmann, Georg Baselitz, A.R. Penck and MarkusLüpertz illustrate the potential and limitations of Ramanmicroscopy and the need for complementary techniques,especially in the case of mixtures. Selected organic pigments,especially Pigment Green 7, Pigment Violet 23 orPigment Yellow 83, are briefly discussed with respect totheir use in artists' paints.