woof

The woof, or weft, is the yarn that runs perpendicular to the warp in any woven fabric. While warp threads run lengthwise down the loom and stay under tension, the woof is inserted horizontally across the warp threads in each pass of the shuttle or gripper. The woof binds the warp into a stable cloth; without it, you have only parallel threads hanging.

In power looms, the woof travels back and forth through the shed, the opening created when warp threads separate into upper and lower layers. Traditional shuttle looms pass a bobbin of woof through this shed in a boat shaped carrier. Modern projectile and rapier looms fire or push the woof directly through without a shuttle, allowing faster speeds and finer control of tension. Water jet and air jet looms use compressed fluid to carry the woof strand across, trading mechanical simplicity for precision in delicate fabrics.

Tension, count, and breakage

The woof yarn must be wound at consistent tension on bobbins to prevent slack or breakage mid weave. Woof tension that is too high breaks the thread; too low leaves loose picks and weak spots in the cloth. The woof count, or number of picks per inch, determines fabric density and weight. A closely set woof with fine yarn creates tight, durable cloth; a loose woof spacing produces lighter drape. Woof breaks during weaving stop production and leave visible defects.

The term woof derives from old English and Germanic roots meaning to weave or twist together, distinct from warp which means to throw or cast forward. In plain weave, the simplest and most common structure, each woof pick alternates over and under every other warp thread. In twill and satin weaves, the woof follows more complex paths across groups of warp threads, creating the diagonal lines or smooth faces characteristic of these fabrics.

Mills select woof fiber, twist, and count based on the intended fabric performance and appearance. Cotton, polyester, wool, and nylon are common woof materials, often different from the warp fiber in the same cloth. A cotton warp with polyester woof, for example, balances cost and durability. The woof yarn is typically softer and less twisted than the warp, since it carries less mechanical stress once in the cloth.