Wasserretting

Wasserretting, or water retting, is a retting method used to separate bast fibers from the woody core of plants such as flax, hemp, and jute. In water retting, harvested stems are bundled and submerged in running or standing water for several days to weeks. Microbial communities and endogenous enzymes in the water degrade pectin and other substances that bind fibers to the stem, loosening the fiber bundles. After retting, mechanical processes such as breaking, scutching, and hackling separate the fibers from the core.

The conditions influence fiber quality: temperature, oxygen content, and water cleanliness affect microbial activity. Low temperatures slow retting; high temperatures speed it but can weaken fibers. The method is relatively low-energy compared to chemical or steam retting, but it requires large volumes of water and appropriate wastewater management. Poorly managed retting can produce odors and pollutants, and untreated effluent can cause environmental harm.

Common crops processed with water retting include flax for linen and jute; in flax processing, retting occurs in dedicated ponds or tanks, and dew retting may be used in the field to reduce water use. In modern industry, alternative retting methods include enzymatic retting, chemical retting, and mechanical extraction, sometimes used in combination to optimize fiber quality and environmental impact. Water retting has a long history in European linen production, though environmental and wastewater considerations have driven modernization and stricter controls.