Micro-Raman and particle-induced X-ray emission spectroscopy for the study of pigments and degradation products present in 17th century coloured maps

Three different maps of the 17th century, two of them of Portugal and the third of the Iberian Peninsula, all of them hand coloured and of Dutch manufacture (copper engraving), were studied in this work. The study was carried out by using particle-induced X-ray emission (PIXE) and micro-Raman spectroscopy. These are two non-destructive techniques that provide complementary information on the composition of the materials: PIXE giving elemental information and Raman providing information at a molecular level. By means of the two techniques it has been possible to identify the inorganic pigments used in the three maps, as well as some products of degradation whose causes are not completely understood yet. This article contributes to a better knowledge of the techniques and palettes used for the colouring of maps of this period as well as the degradations of the pigments. Particular attention is given to the presence of a copper oxalate found in two different maps, its presence being associated with green coloured areas and indicating a degradation of a copper-based green pigment.