Mapping pigments and binders in 15th century Gothic works of art using a combination of visible and near infrared hyperspectral imaging

Visible and near infrared hyperspectral imaging have allowed unprecedented analyses of two major works of art of the National Museum of Catalan Art (MNAC), 15th century Gothic altarpieces: (1) Madonna of the `Consellers' (Lluis Dalmau, 1443-1445) [1], an impressive piece of Catalan painting, inspired by J. van Eyck and (2) Princess Eudoxia exorcised in front of St. Stephen's tomb (Vergos Group, 1495-1500) part of the altarpiece of Sant Esteve de Granollers. Visible and near infrared (VNIR) hyperspectral imaging was used to highlight the artist's handling of materials in achieving light and shadow effects in the red draperies. The refinement in the modelling could be observed thanks to the distribution images of the red pigments. Short-wavelength infrared (SWIR) hyperspectral imaging revealed blackened azurite on visually altered areas of the two paintings. It is possible to map the presence of azurite below the altered layer and obtain a better understanding of the earlier appearance of the paintings. It was moreover possible to identify and map the binders used in both works of art: the use of oil in Dalmau's painting, as the earliest Catalan oil painting, is confirmed here whereas in the Vergos's painting both egg and oil may have been used in separate areas.