Differentiation black pigments in “maja and celestina”, a painting on alabaster by francisco de goya

Identifying and characterising the pigments forming part of a work of art is particularly relevant for the chronological authentication of a painting, as well as knowledge of the great masters artistic resources, which could result in the work being catalogued. The aim of this research is to morphologically characterise and differentiate two black pigments of an organic nature, which are intrinsically mixed together and compacted by a binder. These pigments are part of a black monochrome painting on alabaster by Francisco de Goya. The observation with SEM and EDX microanalysis have allowed to identify and morphologically differentiate these two pigments: vegetable black or vine black and carbon black (lamp black). Thus, in the case of vine black pigment, polygonal forms were observed that may indicate the rigid walls characteristic of vegetable cells. Lamp black pigment can be associated withsmall spherical structures, apparently homogeneous, which appear along with the polygonal vine black forms. We have suggested that Goya mixed these two pigments to obtain a more stable pictorial mixture provided by the black vine pigment and a darker color by the lamp black pigment. The two black pigments that were identified are bound together by a mixture of linseed oil and egg, denoting a tempera grassa painting technique. Highlights • This study is based on a painting done on a translucent alabaster plate. • Alabaster is a little used material as support in paintings, although it has been very used in sculptures, altarpieces and covers. • This painting reproduced an original pictorial composition by Goya, using only the colour black. • This innovative study proposes the morphological differentiation of vine black and lamp black pigments. • Both pigments are mixed and bound together forming a single colour. • The morphological differentiation of vine black and lamp black pigments has been undertaken based on original paint samples from an 18th century painting by Francisco de Goya • Via SEM-EDX it has been possible to morphologically differentiate vine black and lamp black pigments based on the cellular structure of the former and the amorphous structure of the latter.