How do you say “Bocour” in French? The work of Carmen Herrera and acrylic paints in post-war Europe

Abstract The Cuban-American artist Carmen Herrera (born 1915) was the subject of a partial retrospective, titled Carmen Herrera: Lines of Sight, held at the Whitney Museum of American Art, New York, in the fall of 2016. On this occasion, it was noted that the artist had listed the binding media for all the paintings in the exhibit as acrylic even though the earliest works date from the late 1940s to early 1950s, when Herrera was in Paris and acrylics were not yet known to be commercially available in Europe. Questioned about the unexpected media assignments, Herrera recalled buying early acrylic paints in an art supply store near her studio in the French capital. Thus, for this study, a selection of five paintings by Carmen Herrera dated from 1948 to 1952, for which there was no sign or record of previous conservation treatments, were analyzed with a variety of non-invasive and micro-invasive instrumental techniques to characterize the painting materials in order to ascertain whether early experimental acrylic formulations might have been used. A preliminary investigation of the elemental composition of the paints entailed non-invasive analysis of the artworks with X-ray fluorescence spectroscopy. Twenty-one paint samples were then removed from selected areas for micro-invasive examination. Fourier-transform infrared spectroscopy and pyrolysis–gas chromatography/mass spectrometry with and without sample derivatization with tetramethyl ammonium hydroxide were employed to gather detailed information on the chemical composition of the binding media. In addition, complementary analyses by Raman spectroscopy and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy were conducted to shed light on the pigments, colorants, and extenders present. Results revealed that the paints are composed of a range of both traditional and modern materials, including: calcite, gypsum, barite, and titanium white (in the form of rutile and anatase); cadmium yellows, oranges, and reds; Pigment Red 83 – the synthetic counterpart of natural dye alizarin (1,2-dihydroxyanthraquinone) – precipitated onto an aluminum-rich substrate; viridian and emerald green; cerulean blue, cobalt blue, as well as Prussian blue; iron-containing earths and umber-based pigments; as well as bone and/or ivory black. More remarkably, a complex progression of organic binders was uncovered: mixtures of modified oils, detected in paintings dated to 1948 and 1949, were gradually replaced or combined with other binding media, such as acrylics (mostly n-butyl methacrylate), polyvinyl acetate, and oil-based alkyds based on ortho-phthalic acid, in works painted during the following three years. Remarkably, the first occurrence of acrylic binders was observed in a painting dated to 1949, well before the date of introduction to the European market of the first acrylic-based paints by George Rowney & Sons in 1963. In addition to offering insight into Herrera's materials and techniques, this study represents a major advancement in the current scholarship regarding the availability and use of acrylic-based artists’ paints in Europe.