The flax fibers are held together in the stems by woody matters and cellular tissue and Retting is a fermentation process that frees the fibers from these materials. Retting may be carried out in one of several ways.
1. Dam Retting :
The flax plants after pulling are tied up in sheaves or beats and immersed for about ten days in water in special am or ponds dug in the ground. This method is commonly used in Ireland.
2. Dew Retting :
The crop is spread in the ground after pulling and left for several weeks wetting by dew and rain encourages fermenting by moulds to take place. Dew Retting tends to yield dark colored fibers. It may be used in regions where water is in short supply. It is commonly practiced in Russia and France.
3. Tank Retting :
After harvesting, the seed bolls are stripped from the steam by reciprocating metal cobs. The de-seeded flax tied in bundle in packed in to concrete tank which are filled with water artificially heated to about 30°C Retting is completed in about three days some of the best and uniform fiber is produced by this process.
4. Chemical Retting :
Retting can also be carried out by treating the flax straw with chemical solution such reagents are caustic soda (NaOH), Sodium carbonate (Na2Co3), Soaps and dilute mineral acids. Its more costly process than biologic Retting and the fiber produced is not better.
Flax fiber Breaking and Scutching:
After Retting the next stage is breaking. The straw (flax) is passed between flutted roller in a breaking machine, so that the woody core broken in to fragments without damaging the fiber running through the stem the broken straw is then subjected to the proc known as “Scutching” which separates the un want woody material from the fiber. This is done beating the straw with blunt wooden or metal blades, either by hand or by machine. The woody matter is removed as shiver which is usually burnt as fuel, leaving the flax in the form of long strands formed of bundles of individual fibers adhering to one another.
After Scutching the fibers are usual combed or hackled by drawing them through sets of pin, each successive set being finer than the previous one. After hackling we get finer as well as coarse fibers, the long fibers are known as line (More than 10 Inch) and the shorter fiber are called tow (Less than 10 inch) Read more about Properties of Flax fiber