Study of the (photo)degradation of ultramarine gouaches in the cut-outs of Henri Matisse and related art materials

We propose to use µXANES spectroscopy at the S K-edge to study the degradation of synthetic ultramarine blue (Na8Al6Si6O24S2) historical pigments used by Henri Matisse (1869 – 1954) in his gouaches. Our study will focus on well-preserved and degraded historical samples from Matisse’s artworks housed in the Centre Pompidou in Paris, alongside mock-ups aged with UV-VIS light and/or humidity. Combined with a systematic EPR study of ultramarine gouaches under UV-VIS irradiation, this approach will elucidate the role of S3∙-/ S2∙- radicals in the alteration of gouache paint layers and will provide new information to aid in the conservation of Matisse’s masterpieces.