WOVEN FABRICS

The interlacing of two sets of yarns may take place in various ways with the production of woven patterns. Most patterns depend on three basic or fundamental weaves, namely the plain weave, the twill weave, and the satin weave. These and their variations are in themselves capable of forming many interesting patterns, but they may also be combined to make highly ornate effects.

[It is usual to make the edges of woven fabrics in a stronger and firmer manner than the body of the cloth; these edges are called selvedges. It is often sufficient to use 15 to 30 warp threads at each side for the selvedge, and to employ yarns of coarser count than those in the body of the cloth.]

Plain Weave: Plain cloth has the maximum number of intersections and is woven on the one up and one down principle. The plain weave is capable of producing a vast number of fabrics according to the types of yarn in warp and welt, and the number of threads per inch. The commonest method of decorating the plain weave is by the use of coloured yarns. About 70% of woven fabrics are based on the plain construction.

With the plain fabrics, four factors are to be borne in mind; the number of ends, the number of picks, the count of warp yarn and the count of weft yarn. Hence it is very difficult to compare the degree of cover of one fabric with that of another without recourse to the device of expressing certain quantities as ratios.

Figure 1: Plain Weaves.

The COVER FACTOR enables this to be done, and the general principle may be illustrated by reference to cotton.

where t is the number of threads per inch, and N is the count of yarn (cotton system).

Fabrics may be constructed from the formula,.

Cover factors are only one aspect of fabric structure; however, they do tend to integrate the six variables of the more formal cloth analysis, namely, threads per inch, counts of warp and welt, and crimp of warp and weft.

Twill Weave: the twill weave has the method of interlacing so as to make diagonal lines across the fabric. [This produces short floats instead of maximum number of intersections.]

Figure 2: Twills.

A simple twill repeats on 3 shafts and is based on the 2/1 principle, i.e. 2 ends up followed by 1 end down, the diagonal line running from left to right at 45°. In the even sided twill, a square construction is employed with the same counts of warp and weft yarns.

The angle of the twill line may be varied by two devices; an increase in the number of ends per inch (or picks), or alternatively, by stepping more than one thread at a time in the repeat. One may have steep twills and reclining twills.

As the interlacing of warp and weft in the twill is less frequent than in the plain weave, a softer and more flexible cloth may be produced. The twill construction is very popular for the manufacture of woollen and worsted fabrics.

Satin Weave: The satin structure is charactcrised by the smooth unbroken surface of the fabric; this is brought about by the floating threads being bound into the cloth in a manner which does not exhibit a twill or rib line. The warp-faced satin weave is termed “satin,” whereas the welt-faced weave is termed “sateen”. It is essential that careful checking (like a chessboard) should take place at the interchange of the warp design and the weft design.

Pile Fabrics: The common pile fabrics may be divided into two chief classes, velveteen and velvet. The former is a weft pile fabric and the latter is a warp pile construction.