Identification of carbon-based black pigments in four South American polychrome wooden sculptures by Raman microscopy

EUGENIA TOMASINI; B. GOMEZ; EMILIA HALAC; MARIA REINOSO; EMILIANO DI LISCIA; GABRIELA SIRACUSANO; MARTA MAIER

Heritage Science

Chemistry Central

Lugar: Bristol; Año: 2015 vol. 3 p. 1 - 8

2050-7445

Introduction: Carbon-based pigments are a group of dark-colored materials, which are classified according to thestarting material used and their manufacturing process. Raman spectroscopy is an ideal technique for the identificationof carbonaceous matter. Carbon-based pigments show broad bands between 1,300 and 1,600 cm−1 but theydiffer in position, width and relative intensity, allowing discrimination between them. The aim of the present studywas the identification of carbon-based pigments in four polychrome wooden sculptures from the Jesuit Mission LaTrinidad in Paraguay.Results: Analysis of the Raman spectral parameters of the polychrome samples and comparison with those ofcarbon-based pigment references allowed the identification of wood charcoal, lampblack, bistre and a black earthpigment. Complementary analysis by infrared spectroscopy and elemental analysis supported the assignments.Conclusions: In this study we have provided new evidence that Raman microscopy is a powerful technique forthe discrimination of carbon-based pigments in works of art. This is the first time that bistre, lampblack and a blackearth pigment are identified in colonial art. The chemical information obtained on the black pigments contributed toincrease our knowledge on available resources and technology used in the manufacture of the polychrome sculpturesat the Jesuit Mission. This information is relevant for our studies on Colonial art.