A multi-analytical characterization of artists' carbon-based black pigments

The most common synthetic carbon-based black pigments can be divided into three main groups on the basis of the material used for their production: bone blacks, vine blacks and lampblacks. This work reports on the physicochemical characterization of the three commercial pigments purchased from Kremer Pigmente (Germany) and Zecchi (Italy) by means of a multi-analytical approach, which included thermoanalytical (thermogravimetry, thermogravimetry coupled with FTIR and differential scanning calorimetry) and spectroscopic techniques (laser-induced breakdown spectroscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy and X-ray powder diffraction). Combining the results obtained from this multi-analytical approach, qualitative and quantitative conclusions are drawn for the first time. Lampblacks are mainly composed of amorphous carbon. In vine black (Kremer), amorphous carbon and cellulose pyrolysis by-products are the main constituents. In bone blacks and vine black (Zecchi), carbonaceous materials are minor components. Hydroxyapatite and calcium carbonate are the main constituents of bone blacks, and iron and magnesium oxides are the main constituents of vine black (Zecchi). Results from this multi-analytical study on the composition of such widespread pigments can provide valuable information in the decision-making process for restorers and conservators.