Extra sets of warps or fillings are woven over ground yarns of plain or twill weave to form loops. Pile fabrics have been defined as “fabrics(s) with cut or uncut loops which stand up densely on the surface” (Klapper 1967,64). Pile fabrics may be created by weaving or through other construction techniques, such as tufting, knitting, or stitch through. To create the loops that appear on the surface of woven pile fabrics, the weaving process incorporates an extra set of yarns that form the pile. Construction of woven pile fabrics, therefore, represents a complex form of weaving in which there are at least three sets of yarns.
Woven pile fabrics are divided into two categories depending on whether the extra set of yarns is in the warp direction or the filling direction. Warp pile fabrics have two sets of warp yarns and one set of filling yarns. Filling pile fabrics have two sets of filling yarns. Pile fabrics are woven by one of several methods, depending on whether they are warp pile or filling pile fabrics.
Warp Pile Fabrics
Warp pile can be made by the wire method, the double-cloth method, or by slack tension weaving.In the wire method one set of warp yarns and the filling yarn interlace in the usual manner and form the “ground” fabric in either a plain or twill weave. The extra set of warp yarns forms the pile. When the pile yarns are raised by the heddles, the machine inserts a wire across the loom in the filling direction. When the warps are lowered, they loop over the wire to make a raised area. The next several filling yarns are inserted in the usual manner. The wire is then withdrawn, leaving the loop, which is held firmly in place by the other yarns. Frieze, a fabric often used for upholstery, is an example of an uncut, looped pile fabric that can be made by the wire method. If the fabric is to have a cut pile, the wire has a knife blade at the end that cuts the yarns as the wire is withdrawn.
Velvets may be made in this way. If the fabric is to have an uncut pile, the wire has no cutting edge. The double-cloth method is used for cut pile fabrics. Here, two sets of warps and two sets of fillings are woven simultaneously into a layer of fabric. A third set of warp yarns moves back and forth between the two layers of fabric, holding them together and being held by each fabric. The resultant fabric is cUt apart by a sharp knife, thereby creating two lengths of fabric, each with a cut pile. Velvets and flushes can be made with the double-cloth method. Velvets are usually made of filament yarns. Other nonpile fabrics can be made by the double-cloth method, and are discussed later.Terry cloth is made by the slack tension method. Terry cloth is made with uncut loops. Usually, two sets of warps and one set of filling yarns are used; however, more expensive fabrics may use two sets of yarns in each direction. The ground of the fabric is of warp yarns held under tension, the pile of warp yarns that are allowed to relax.
Periodically (usually after every three picks), tension is released on the warp pile yarns at the same time as the next three filling yarns are pushed firmly into place. The first two of each three picks are only beaten up part way. The loose warp yarns loop up on the surface to form the terry pile. Loops may remain uncut to form the traditional terry cloth with loops on both sides.
Sometimes one side is sheared to make an attractive velour face. Such fabrics do not wear as well as uncut loop fabrics. Pile yarns in velour toweling tend to become dislodged more easily, thereby shortening the wear life of the material. Terry pile may appear on one or both sides of the fabric.
Filling Pile Fabrics
Filling pile fabrics are woven by the filling pile method. In this method there are two sets of filling yarns and one set of warp yarns. The extra set of filling yarns forms floats that are from four to six yarns in length. The floating yarns are cut at the center of the float, and these ends are brushed up on the surface of the fabric. In some filling pile constructions, the filling yarn that makes the pile is interlaced with the ground one time before it is cut;’ in others, the filling pile interlaces twice. Those fabrics in which there are two interlacings are more durable than when only one interlacing has taken place. Floats for corduroy are placed in lengthwise rows, and floats for velveteen are spaced to produce an overall pile effect. Velveteens are characterized by a uniform, overall pile. The even spacing of corduroy floats produces a strip or wale characteristic of this fabric
Corduroys are given names according to the numbers of wales. Feathercord corduroy has about 20 to 25 lengthwise wales per inch; fine wale or pinwale corduroy, about 16 to 23 wales; mid, medium, or regular wale corduroy, about 14 wales; wide wale corduroy, about 6 to 10 wales; and broad wale corduroy, about 3 to 5 ribs per inch. Novelty wale corduroys are also produced in which thick and thin wales are arranged in varying patterns. Some corduroy fabrics are now made with 100 percent cotton yarns in the pile filling and polyester and cotton blends in the ground yarns. Other decorative effects can be achieved by cutting floats selectively to vary pattern and texture. Most filling pile fabrics are made from spun yarns.