All bast fibres but also some types of cotton have a grey, brownish or beige colour. Home textiles in particular, however, were supposed to be pure white as a sign of cleanliness and good housekeeping.
Freshly woven textiles, but also textiles that had become dirty through use, were therefore subjected to so-called lawn bleaching. On a meadow near a river, the bleaching place or also the cloth bleaching, the wet fabrics, but also yarns, were laid out flat or stretched out and kept continuously moist. To remove greasy components, but also resins and waxes embedded in the fibres, the linen pieces were soaked in potash lye before bleaching or the goods were moistened with ash lye in between. The effect was also enhanced by treatment with sour milk - so-called acidification.
Chemically, lawn bleaching uses a natural phenomenon. When atomic oxygen acts on water, hydrogen peroxide (H2O2) is produced - a powerful bleaching agent. Especially after thunderstorms, it is present in the rain. In addition, the photosynthesis of the lawn on which the textiles lie forms so-called oxygen radicals, which also have a bleaching effect.
It took up to six months until a linen fabric was almost completely white and it had to be turned at least once.
Then came the second thorough wash with ash lye to remove any stains that may have developed during the long bleaching time.
These videos show how a washing day and bleaching were carried out in Germany and Austria until the 1960s:
https://www.youtube.com/watch?v=9WqBDqSvjb4
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