Abstract
A variety of techniques were used to investigate flax yarns sampled from four selected Italian paintings on canvas dated between the 17th and 18th centuries and compare them with a modern flax yarn. The goal was to establish their state of preservation and highlight the critical issues thanks to a combined approach that used SEM, atomic force microscopy, nanoindentation, nuclear magnetic resonance, second harmonic generation imaging microscopy and FTIR spectroscopy. The condition of the flax fibres was assessed, and the results showed that two of the four canvases were in a generally good state of preservation, while the other two exhibited signs of biological attack and brittleness due to a previous relining intervention.