tram

Tram is a composite silk thread made by twisting two or more single silk filaments together. In velvet and silk fabric production, it serves as the weft, the horizontal thread that interlaces with the warp to form the cloth structure. The twist gives it strength and a characteristic luster that contributes to the finished fabric's quality and appearance.

The term appears most often in high-grade velvet manufacturing, where tram is preferred over single-strand weft because it reduces breakage during the loom cycle and produces a more uniform pile. A typical tram might consist of two twisted filaments, though heavier constructions use three or four strands. The twist direction and tightness affect how the thread behaves in the weave and how the final pile stands.

Tram differs from singles, which is an untwisted filament, and from organzine, which is a warp thread made by twisting together already-twisted singles. Because tram is used as fill rather than foundation, it need not have the same tensile strength as warp threads, but it must still survive the repeated friction of being shot across the loom thousands of times per hour.

The word tram itself has uncertain etymology but is documented in English textile trade vocabulary by the 17th century. It may derive from an obsolete term for a thread or line, or possibly from Italian or Flemish sources reflecting early European silk weaving centers. Within the trade, "tram" is sometimes used loosely to mean any weft thread, though technically it refers only to twisted constructions intended for fine work.

In modern production, tram has become less common as synthetic filaments and power looms have changed textile economics. Natural silk tram is now found mainly in heritage velvet manufacture, period costume reproduction, and premium furnishing fabrics where the characteristic handle and appearance justify higher costs. Industrial velvet for upholstery or automotive use typically employs synthetic weft of different construction.