Weft

Weft and Warp Working Together

No woven fabric exists with weft alone. Cloth is the result of two sets of yarn meeting at right angles: the warp, held lengthwise under tension on the loom, and the weft, carried across it row by row. The warp provides the structure and must withstand being stretched, held taut and repeatedly separated into openings through which the weft passes. The weft provides the filling. It travels across, turns at the edge, and travels back, building the fabric one pass at a time. That division of labor explains the names and the properties of each set. Weft is also called woof or fill, both words describing what it does: it fills the spaces between the warp threads and completes the surface of the cloth.

Because the weft is not stretched the way the warp is, it can generally be less strong. That single fact gives weavers useful freedom. A yarn too soft, bulky, textured or delicate to survive as warp can still serve as weft, where it sits protected between warp threads and shows on the surface of the finished fabric. Pattern, color effects and surface texture in woven cloth very often come from the weft for exactly this reason: the weft is where a weaver can afford to experiment, while the warp must first of all be dependable.

Shuttles, Looms and the Speeding of Weaving

The weft is threaded through the warp using a shuttle, a carrier that holds the yarn and is passed from one side of the loom to the other. Hand looms were the first weaving tool, with the shuttle being threaded through alternately raised warps by hand. Alternately raised is the key action: some warp threads are lifted and others lowered, opening a gap, and the shuttle carries the weft through that gap. The next pass reverses the raised and lowered threads, locking the previous row in place. Repeated thousands of times, that simple alternation is what turns two sets of loose yarn into a single coherent fabric.

Inventions during the 18th century spurred the Industrial Revolution in weaving. The flying shuttle sped up production of cloth by propelling the shuttle across the loom instead of passing it by hand, and water power was then used to automate the weaving process. The power loom followed in the 19th century, when steam power was harnessed. Each step mechanized the same essential weft action, carrying yarn across the warp, but did it faster and on a larger scale. The principle visible on a hand loom and the principle inside an industrial loom are the same; only the speed, force and consistency changed.

Fibers Used for Weft

The weft is a thread or yarn of spun fiber. The early fibers were wool, flax and cotton, the same natural fibers available for the warp, and nowadays man-made fibers are also used in weaving. The choice of weft fiber affects how a fabric feels, drapes, absorbs moisture and takes color, because weft yarns make up much of the surface a wearer touches. A fabric can also combine fibers, using one fiber in the warp for strength and another in the weft for softness or appearance. Counting the weft passes in a given length of fabric, expressed as picks per inch, is a standard way to describe how densely a cloth is woven: more picks generally mean a fuller, more closely packed fabric. Picks per inch also helps compare fabrics made for different uses, because a loosely filled cloth drapes and breathes differently from a tightly filled one, even when both use similar yarns. Together with the count of warp ends per inch, it gives a practical shorthand for the balance between the two directions of yarn that make up the cloth.