retting

Water retting

The most widely practiced method of retting, called water retting , is performed by submerging bundles of stalks in water. The water, penetrating to the central stalk portion, swells the inner cells, bursting the outermost layer, thus increasing uptake of both moisture and decay-producing bacteria. Retting time must be carefully judged; under-retting makes separation difficult, and over-retting weakens the fiber. In a double retting, a gentle process producing excellent fiber, the stalks are removed from the water before retting is completed, then retted again. ^[1]

Natural water retting employs stagnant or slow-moving waters, such as ponds, bogs, and slow streams and rivers. The stalk bundles are usually low, usually with stones or wood, for about 8 to 14 days, depending on water temperature and mineral content. ^[1]

Tank retting , by contrast, is usually made in concrete, and is feasible in any season. In the first six to eight hours, called the leaching period, much of the dirt and coloring is removed by the water, which is usually changed to ensure clean fiber. Rinse water, which requires treatment to reduce the risk of toxicants before its release, is rich in plant minerals, such as nitrates, and can be used as liquid fertilizer. ^[1]

Dew retting

This is a common method in areas with limited water resources. It is most effective in warm weather and warm daytime temperatures. The harvested plant stalks are spread evenly in grassy fields, where the combined action of bacteria, sun, air, and dew occurs, dissolving much of the stem material surrounding the fiber bundles. Within two to three weeks, depending on climatic conditions, the fiber can be separated. Dew-retted fiber is the darker in color and of poorer quality than water-retted fiber. ^[1]

After retting

The retted stalks, called straw, are dried in open air or by mechanical means, and are often stored for a period of time to allow “curing” to occur, facilitating fiber removal. Final separation of the fiber is accomplished by a breaking process in which the woody brittle portion of the straw is broken, or by hand by passing through rollers, followed by the scutching operation, which removes the broken woody pieces (shives) by beating gold scraping. Some machines combines breaking and scutching operations. The first scutching of the first scutching of fibers and short fibers. The short fiber ( tow) thus obtained is frequently used in paper manufacture, and the shites may be used as a wallboard. ^[1]

References