Tracing the ¹⁴ C bomb peak in Pierre Soulages’ artworks to improve radiocarbon dating of 20th century paintings

Abstract Flax plays an important role in art, especially for painters. Flax seeds are ground into linseed oil, which is used as binder for oil paints, and fibers are used to make linen canvas as a support for paintings. Because of the rapid growth of flax, linen canvas fiber and linseed oil are considered good candidates for the radiocarbon ( 14 C) dating of paintings. However, the time necessary to transform flax into a linen canvas must be estimated in order to determine the completion date of paintings. Based on the paintings of the French painter Pierre Soulages (1919–2022), who titled his works with the day on which he considered them finished, the time elapsed between completion of the painting and harvesting of the flax was determined for 25 canvases and 13 oil binders. For the canvases, three periods can be distinguished between 1956 and 1981 with durations of 5±1 years in the 1950s, 3±2 years in the 1960s and 11±3 years for the paintings from the 1970s–1980s. For the oil, the time elapsed between the date indicated by the artist and the 14 C calibrated date has a mean value of 3±2 years in the 1950s and 1960s and more than 15 years in the 1970s. These long time lags could be due to the massive change in flax processing, which was relocated, resulting in longer times between flax harvesting and canvas marketing. The determination of these time lags enables us to better interpret the 14 C dating results for the paintings.