About Twist Direction

Twist Direction:
The direction of the twist at each stage of manufacture is indicated by the use of letters S or Z in accordance with the following convention. Twist may be performed in the following two directions (see Figure 2).

S direction: A single yarn has ‘S’ twist (clockwise) if, when it is held in the vertical position, the fibers inclined to the axis of the yarn conform in direction of slope to the central portion of the letter S.

Z direction: A single yarn has ‘Z’ twist (anticlockwise) if, when it is held in the vertical position, the fibers inclined to the axis of the yarn conform in direction of slope to the central portion of the letter Z.

As can be seen from the diagram (Figure 1), by holding the yarn upright, the slope of the middle of the yarn should flow in the same direction as the slope of the middle of the letters S or Z. The majority of single yarns are Z, but the direction does not really affect the property of the yarn. However, in a plied yarn, the direction is important because the single yarn should be in one direction but when two yarns are combined to make the ply it is running in the opposite direction; this ensures that the yarn holds together.

For example, 2 x S single yarn + Z ply = stable, smooth, firm, tight and durable yarn suitable for weaving; worsted yarns often possess a high-angled twist.

2 x Z single yarn+ S ply = stable, soft, bulky yarn suitable for knitting. It often has a low-angled twist.
2 x S single yarns + S ply = an unstable yarn that will snag and curl.
2 x Z single yarns + Z ply = unstable yarn that will snag and curl.