Direction of the Twist in Yarns.—Warp yarns are usually twisted so as to show the lines of the twist from right to left, and weft yarns are twisted in the opposite direction. The reason for this is that when the yarns are woven into cloth the lines of both warp and weft run in the same direction, and the threads become embedded together as closely as possible through the strands falling into each other. This is shown at [Fig. 405], where at A and B the warp and weft yarns are shown laid side by side. At C the same yarns are shown as laid in the cloth, when it will be seen that the lines of twist appear in the same direction, and the threads have thus a chance of getting together as closely as possible.
If the weft is spun in the same direction as the warp, or “twist way,” as it is termed, when woven the lines or strands appear in opposite directions, and each thread has a tendency to be kept apart from the others, and appears separately. This, if anything, makes the cloth feel slightly thicker, and is preferred by many for certain purposes, including some classes of printing cloths. The finer appearance is obtained by the yarns spun in opposite directions.
FIG. 405.
FIG. 406.
In twill and satin cloths, and similar fabrics, the direction of the twist has a very important bearing upon the appearance of the fabric.
The finest and closest effect is obtained by using warp and weft yarns spun in opposite directions, so that when woven the lines appear in the same direction, and the direction of the twill should be opposite to both. This is why one side of a twill cloth has a finer appearance than the other, as the twill runs against the lines on one side, and with the lines on the other side of the cloth, the former having the finer appearance. [Fig. 406] shows the yarns spun oppositely, and the twill running in a direction opposite to the lines.
In sateen cloths there is a kind of twill in one direction, as shown in [Fig. 407], and the above principle applies to this as well as regular twills.
