yb

Yarn backward, or yb, is a weaving technique where yarn is threaded through the loom in the opposite direction from the standard forward pass. Instead of following the normal warp path from one side of the loom to the other, the weaver runs yarn back through already-threaded sections, reversing the mechanical direction to create specific pattern effects or repair broken warps without stopping production.

The method is most common in narrow-ware looms and shuttle looms where weft insertion is manual or semi-automatic. A weaver will yb when a warp thread breaks mid-production and needs replacement, or when a color pattern demands that yarn enter the shed from an unexpected angle. On jacquard and dobby looms, yb is sometimes used to correct threading errors in the harness without a full loom restart, which can save hours of downtime on complex patterns.

When and why it matters

Yarns vary in how they tolerate backward threading. Fragile filament yarns, especially fine silk or nylon, can fray or snag if pulled backward through heddles and reed without care. Staple-fiber yarns like cotton or wool are more forgiving. The tension required is often higher on a yb pass because the yarn is fighting the natural set of the loom's threading; loose tension results in slack weft and pattern distortion.

The term appears in written mill procedures and loom logs as shorthand, usually marked with a line number or harness position so that supervisors know which sections were threaded in reverse. It is not a preferred method for long runs, since it slows throughput and introduces a point of failure if the yarn catches or breaks during the backward pass. Most mills reserve yb for emergency repairs and small decorative insertions where the extra labor cost is justified by avoiding a full harness re-thread.