FABRIC STRUCTURE AND DESIGNING The following classification will be adopted : Group 1, to include all fabrics made from one warp and one weft, provided both sets of threads remain parallel in the finished article and are intersected to give the requisite feel and appearance. Group 2, to include (a) fabrics constructed from two warps and one weft, or two wefts and one warp, as in those that are backed, reversible and figured with extra material; (b) two or more distinct fabrics built simultaneously from two or more warps and wefts, as in two, three and other ply cloths; (c) fabrics built by so intersecting two or more warps and wefts that only one texture results, as in loom made tapestries and figured repps. Group 3, to include fabrics in which a portion of the weft or warp rises vertically from the ground-work of a finished piece, as in velveteens, velvets, plushes and piled carpets. Group 4, to embrace all fabrics in which one portion of the warp is twisted partially, or wholly, round another portion, as in gauzes and lappet cloths.
The structure of a cloth, and its ornamentation by weaving, is worked out by the cloth designer on squared paper. Successive vertical lines of squares are taken to represent the warp threads, whilst horizontal lines similarly represent weft threads. A filled-in square then indicates that the warp thread it represents is above the weft, whereas a blank means weft above warp. This can be seen clearly in fig. 1. When two or more warps or wefts are used in a cloth, different colours or kinds of marks are generally used to show the working of the different warps or wefts. Thus, in fig. 15 the crosses represent ground warp above ground weft, whereas the filled squares show ground warp above the extra or figuring weft.
cloth. Such a fabric would, therefore, appear to admit of but slight ornamentation, yet this is by no means the case, for if thick and thin threads of warp and weft alternate the resultant fabric may be made to assume a corrugated appearance on the face, while beneath it remains flat, as in poplins, repps and cords. A plan and a longitudinal section of a repp cloth are shown in fig. 2. Colour may also be employed to ornament plain fabrics, and its simplest application produces stripes and checks. But colour may con vert these fabrics into the most artistic productions. Tapestries only differ from simple plain cloth in having each horizon tal line of weft made up of numerous short lengths of parti-coloured thread. Many fine specimens of this art have been re covered from ancient Egyptian and Peruvian tombs, and many are still produced in the Gobelins and manufactories of Europe.
Twills are next in importance to plain cloth on account of their wide range of application and great variety of effects; in elabo rately figured goods their use is as extensive as where they provide the only ornament. Twills invariably form diagonal ribs in fabrics, and these are due to the intervals at which the warp and weft are intersected; thus two or more warp threads are passed over or under one or more than one weft thread in regular succession. Twills are said to be equal when similar quantities of warp and weft are upon the face of a fabric, unequal when one set of threads greatly preponderates over the other set. Fig. 3 shows the design for an equal, and fig. 4 that for an unequal twill, each of which requires four warp and weft threads to complete the scheme of intersections. If the ribs form angles of 45 degrees, the warp and weft threads per inch are about equal in number, but for an unequal twill the material most in evidence should be closest and finest. The angle formed may be greater or less than 45 de grees, as in figs. 5, 6, which are both de rived as shown from the same base weave.