WCO Explanatory Notes reproduced for reference. © World Customs Organization. Verify against official WCO publication.
50.04 - Silk yarn (other than yarn spun from silk waste) not put up for retail sale. This heading applies to thrown silk, i.e., yarns obtained by twisting (either singly or two or more together) the raw silk threads of heading 50.02. I) The are, however, excluded if put up for retail sale heading 50.06 or if within the definition of twine, c a d g e , eAc. (heading 56.07) (see Parts (I) (B) and (3) o the General Explanatory Note to Section XI). The yarns of this headin differ from the yarns spun fi-om silk waste classified in the following headlng in that they are ormed of continuous fibres. There are many varieties, including : ? (I) Single yarns (sometimes known as oils), obtained by twisting a single raw silk thread. # Hard-twisted yarns of this type are o en called crepe poils, mousselines or chiffon twist. (2) Tram yarns, obtained by loosely twisting two or more unthrown raw silk threads; these are used as weft yarns. (3) " Crepe twist ", generally a hard-twisted tram. (4) Organzine yarns, obtained from two or more raw silk threads which have been well twisted in the single b doubling them with reverse twist. Grenadine yarn is a hard-twisted organzme. T ese are used mainly as warp yarns. K All these yarns may be discharged or finished. The heading excludes imitation catgut of silk, of heading 56.04.
Silk GENERAL The General Explanatory Note to Section XI should be taken into account in reading the Explanatory Notes to this Chapter. P For the urposes of this Cha ter the term " silk covers not only the fibrous matter secreted by the Bom%yx mori mulberry eeding silk-worm), but also the products of the secretion of similar insects e.g., Bom yx textor known as wild silk. Among the wild varieties, so named because the pro ucmg worm has on y very rarely been domesticated, the most important is tussah silk obta~nedfiom a silk-wonn that feeds on oak. Spider silk and marine or byssus silk (the filaments by which certain shellfish of the Pinna family cling to rocks) are also classified in this Chapter. Generally speaking, this at its vmous stages of silk-worm gut. " ter covers silk, including mixed textile materials classified as silk, from the raw material to the woven fabric. It also includes