Retting

When roasting or Rotten (formerly Röthen ) refers to one of the operations for the extraction of plant fibers during industrial hemp, flax, jute and other bast fiber by fiber digestion. During roasting, the pectins are dissolved in the plant stems. This, Pflanzenleim ' connects the fibers of the solid wood components of the plant. In subsequent processes (crushing, Swinging, Panting ) then the individual components are separated.

The word roasting has its origin in rotten, rotting that is, 'red' are ( Red originally denoted a more brownish hue ). The process gives the fibers the typical gray -brown to flaxen color, while unroasted flax ( flax green ) is yellowish and can be processed worse.

Biological retting

When Tauröste, also called Feldröste, the cut or gerauften plant stalks are laid out on the field or a meadow. The dew favors the development of micro-organisms ( mainly bacteria) that dissolve the pectin. This process continues for several weeks. It is environmentally favorable because the induced components pass into the ground and needs less fertilizer when re- planting of the field. The Tauröste is just as risky as the entire fiber crop can be destroyed by excessive rainfall. Despite everything, she is the most important process in the production of flax fiber (linen)

The water retting is carried out in open water in ponds ( flax retting sites ) or tanks. The plants are either several days in warm water ( Warmwasserröste ) or two to three weeks in cold water ( cold water retting ). This form of retting heavily loaded waters, but due to the lower time required often more economical.

Chemical retting

In the chemical retting the pectin is achieved with the aid of chemicals and heat. Are used for this purpose, for example, sulfuric acid, sodium hydroxide or chloride of lime. The process is extremely fast ( half an hour compared to several days at the Warmwasserröste ) and easy to control. However it is very costly and the fibers are highly stressed. Therefore, this method has been unable to enforce.

Physical digestion

In addition to the biological and chemical retting is also the possibility of the fibers by a physical vapor pressure digestion ( steam explosion ), or to separate by digestion by means of ultrasonics.