Retting

Retting is the process of loosening the bast fibre from the core material in the plant stalk. Traditionally, it was carried out in designated ponds, reservoirs and slow-flowing streams or rivers and was one of the activities that influenced the character of rural areas throughout Europe. In the industrial scutching mills of the mid-20th century, the water-retting process was carried out in special tanks. With the resurgence of hemp farming in Western Europe, water-retting was abandoned in the face of unresolved wastewater treatment and the process moved to the fields.

When performed on the field, this process is known as "dew-retting." Following harvest, the hemp straw remains on the land for several weeks, allowing microorganisms to facilitate the degradation of the glue layer, which consists of hemicellulose and pectin, between the bast fibres. This microbial activity is aided by water exposure, including rainfall and dew. During the retting process, the hemp is periodically turned to ensure uniform and optimal retting.

By weakening the glue layer, known as the pectin layer, individual fibres and core material (shives) can be effectively separated during subsequent processing steps. The duration of retting varies depending on weather conditions, as decomposition is influenced by factors such as rainfall, dew, and temperature. For technical purposes, retting typically lasts around two weeks, with the stems being turned two to three times. In contrast, for textile applications, retting can extend to five to six weeks, with the stems being turned once or twice.