Bast fibre

Bast fibre (also called phloem fibre or skin fibre) is plant fibre collected from the phloem (the "inner bark", sometimes called "skin") or bast surrounding the stem of certain dicotyledonous plants. It supports the conductive cells of the phloem and provides strength to the stem. Some of the economically important bast fibres are obtained from herbs cultivated in agriculture, as for instance flax, hemp, or ramie, but also bast fibres from wild plants, as stinging nettle, and trees such as lime or linden, wisteria, and mulberry have been used in the past.[1] Bast fibres are classified as soft fibres, and are flexible.[2] Fibres from monocotyledonous plants, called "leaf fiber", are classified as hard fibres and are stiff.[2]

Flax stem cross-section, showing locations of underlying tissues. Ep = epidermis; C = cortex; BF = bast fibres; P = phloem; X = xylem; Pi = pith
Women in southern Norway weaving with linden bast fibres
Ndimbu mask from Tanganyika, made with wood, hair and bast

Since the valuable fibres are located in the phloem, they must often be separated from the xylem material ("woody core"), and sometimes also from the epidermis. The process for this is called retting, and can be performed by micro-organisms either on land (nowadays the most important) or in water, or by chemicals (for instance high pH and chelating agents) or by pectinolytic enzymes. In the phloem, bast fibres occur in bundles that are glued together by pectin and calcium ions. More intense retting separates the fibre bundles into elementary fibres, that can be several centimetres long. Often bast fibres have higher tensile strength than other kinds, and are used in high-quality textiles (sometimes in blends with cotton or synthetic fibres), ropes, yarn, paper, composite materials and burlap. An important property of bast fibres is that they contain a special structure, the fibre node, that represents a weak point, and gives flexibility. Seed hairs, such as cotton, do not have nodes.

Etymology

The term "bast" derives from Old English bæst (“inner bark of trees from which ropes were made”), from Proto-Germanic *bastaz (“bast, rope”). It may have the same root as Latin fascis ("bundle") and Middle Irish basc ("necklace").[3][4]

Use of bast fibre

Plants that have been used for bast fibre include flax (from which linen is made), hemp, jute, kenaf, kudzu, linden, milkweed, nettle, okra, paper mulberry, ramie, and roselle hemp.

Girl in a dress of bast fibre, Rio Chimoré, Bolivia 1908–1909.

Bast fibres are processed for use in carpet, yarn, rope, geotextile (netting or matting), traditional carpets, hessian or burlap, paper, sacks, etc. Bast fibres are also used in the non-woven, moulding, and composite technology industries for the manufacturing of non-woven mats and carpets, composite boards as furniture materials, automobile door panels and headliners, etc. From prehistoric times through at least the early 20th century, bast shoes were woven from bast strips in the forest areas of Eastern Europe.

Where no other source of tanbark was available, bast has also been used for tanning leather.[5]

References
  1. Mary Dusenbury (1992), "A Wisteria Grain Bag And Other Tree Bast Fiber Textiles Of Japan", Textiles in Daily Life: Proceedings of the Third Biennial Symposium of the Textile Society of America, September 24–26 1992
  2. Esau, K. (12 January 1977). Anatomy of seed plants. New York: John Wiley and Sons. ISBN 978-0-471-24520-9.
  3. "the definition of bast". www.dictionary.com.
  4. Bailey, Nathan (1736). "Dictionarium Britannicum Or a More Compleat Universal Etymological English Dictionary Than Any Extant". T. Cox – via Google Books.
  5. "Production of Russia Leather" (PDF). The Honourable Cordwainers' Company. 1807. p. 2. Archived from the original (PDF) on 4 March 2016. Retrieved 10 October 2013.

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