9/10/2023 0 Comments White carbon blackRaman spectroscopy is an ideal non-destructive technique for the characterization of a variety of carbonaceous materials because it is sensitive to crystalline and amorphous structures, allowing the study of highly disordered materials, such as carbon-based pigments. As the precise identification of pigments is important for understanding the technology employed in the manufacture of an artwork as well as the resources available, an unambiguous characterization of carbon-based pigments remains a big challenge. In most cases, the pigment was assumed to be charcoal or simply “carbon black”, a term generally used to mean any pigment based on carbon. Ĭarbon-based pigments have been identified in archaeological artifacts, rock art, and in easel and wall paintings. These humic-earth materials are composed of complex mixtures of natural organic substances derived from animal and vegetable sources with varying proportions of mineral matter. On the other hand, black earths containing amorphous carbonaceous materials, such as Vandyke brown and Cassel earth have also been used as pigments. They are composed by some form of elemental carbon and four groups may be distinguished: graphite, flame carbons, chars, and cokes. This information is relevant for our studies on Colonial art.Ĭarbon-based pigments are a group of dark-colored materials that are classified according to the starting material and the manufacturing process. The chemical information obtained on the black pigments contributed to increase our knowledge on available resources and technology used in the manufacture of the polychrome sculptures at the Jesuit Mission. This is the first time that bistre, lampblack and a black earth pigment are identified in colonial art. In this study we have provided new evidence that Raman microscopy is a powerful technique for the discrimination of carbon-based pigments in works of art. Complementary analysis by infrared spectroscopy and elemental analysis supported the assignments. ResultsĪnalysis of the Raman spectral parameters of the polychrome samples and comparison with those of carbon-based pigment references allowed the identification of wood charcoal, lampblack, bistre and a black earth pigment. The aim of the present study was the identification of carbon-based pigments in four polychrome wooden sculptures from the Jesuit Mission La Trinidad in Paraguay. Carbon-based pigments show broad bands between 1,300 and 1,600 cm −1 but they differ in position, width and relative intensity, allowing discrimination between them. Raman spectroscopy is an ideal technique for the identification of carbonaceous matter. Carbon-based pigments are a group of dark-colored materials, which are classified according to the starting material used and their manufacturing process.
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