When the study of ancient fibers sheds light on the current uses of linen

View of individual flax fibers under an electron microscope. On the leftmost fiber, two “knees” are visible (white streaks). At the level of these zones of geometric irregularities, the behavior of the fibers in tension is altered. These defects also increase the porosity of the fibre: water or microorganisms can infiltrate it, damaging the stem. JOHNNY BEAUGRAND

On the art of putting the antique at the service of modern. French teams have analyzed 4,000-year-old mortuary linen found in Egyptian sarcophagi, and samples of Italian canvases from the 17^e and 18^e centuries. The way in which these flax fibers have aged should help, hope the researchers, to understand the behavior of modern flax, once incorporated into composite eco-materials.

Let’s take a brief look back at the long history of linen. Although it often refers to the Egypt of the pharaohs, this textile fiber has forged even more ancient ties with man. Tiny flax fibers dated to 38,000 years ago were found in a cave in Georgia in 2009. They bore traces of twists and pigments and would represent the first known textile produced by our species.

Around 3,000 years before our era, linen became the emblematic textile of Egyptian High Antiquity. Then the Phoenicians, great navigators, introduced this plant to Greece, Rome, Brittany, England, Ireland… from 1,200 years before our era. In 789, Charlemagne gave a strong impetus to the craftsmanship of these fibers, ordering that each household in France obtain the tools necessary to work it. In the XIII^e century, a weaver named Baptiste, born near Cambrai, perfected a weaving process of great finesse. The linen “batiste” then becomes the “cloth of kings”. This textile reached its peak in the 17th^e century, then was gradually replaced by cotton and declined strongly in the XIX^e century. He will return to favor in the second half of the XX^e century, driven by varietal selection and the mechanization of agriculture and scutching.

Stiffer and more fragile fibers

Let us return to the analysis of old linens. In 2021, Alain Bourmaud’s CNRS team from the University of Bretagne-Sud first showed that funeral linen four thousand years old, extremely well preserved thanks to the temperature and humidity of the tombs, retain very good mechanical properties. However, the structural defects of their fibers “are much more pronounced than those of modern flax fibres”emphasizes this materials specialist. “These old fibers have become a little stiffer and a little more brittle than modern fibers, because their less stable constituents, pectins and hemicelluloses, have been degraded”he says.

Magnification of a damaged area reveals the internal network of the fiber, with its reinforcement of cellulose microfibrils. JOHNNY BEAUGRAND

For this work carried out in collaboration with the Soleil synchrotron (Essonne), the Femto-ST institute (Doubs), the Louvre Museum, Inrae in Nantes and the universities of Montpellier and Cambridge, the researchers used a battery of non-destructive techniques. For example, atomic force microscopy (AFM) has made it possible to map the surface of fibers, at the nanometer scale, and to map their stiffness. Two-photon microscopy (2PEF), meanwhile, explored the organization of cellulose, a long molecule that makes up 80% of flax.

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