Twist is the primary binding mechanism for spun yarns. The amount and direction of twist influences many yarn and fabric properties. For knitting yarns, less twist is preferred to produce softer yarns and fabrics. Twist also affects strength, elongation, hairiness, torque, and cover factor. Maintaining a consistent twist level within 3.5% CV is important to avoid quality issues. The formation of spirality in knitted fabrics can be reduced through methods like using low-twist yarns, balanced plied yarns, or alternating S-twist and Z-twist yarns in the feeders.

1. Yarn
Technical Specifications & selection
guidelines

2. Technical Specifications

3. Yarn Twist

Twisting is the primary binding mechanism of spun
yarns.

In general, twist is defined as a measure of spiral turns
given to a yarn in order to hold the constituent fibers
together.

In practice, yarn twist is described using three main
parameters:
• (a) twist direction,
• (b) twist level (turns/unit length), and
• (c) twist factor

4. Yarn Twist

The amount of twist inserted in the yarn can influence
many yarn characteristics.

It is, perhaps, the only binding mechanism that allows
the structure to retain a great deal of its flexibility (as
compared to glue or adhesive chemicals which result in
more stiff structures).

5. Yarn Twist

Highly twisted yarn is “Lively” and tends to twist upon it
and produce “Snarls”.

Fabrics made from highly twisted yarns will possess a
lively handle.

In general, the higher the level of twist in the yarn the
greater the tendency for the knit fabric to skew or
torque.

An increase in the amount of twist produces an increase
in the yarn strength, if yarn strength is increase, the
fabric strength will be increased.

6. Yarn Twist

The warp yarns are the yarns with highest twist.

The twist of weft yarns is approximately 4 - 5 % below
the twist of warp yarns.

The twist of hosiery yarns is approximately 12 – 15 %
below the twist of warp yarns.

A fine yarn requires more twist than a coarse yarn for the
same application.

7. Twist Multiplier ( TM)

The twist multiplier is an expression of the twist level
adjusted for yarn count.

The commonly used formula to determine the twist
multiplier of yarn for a given yarn count and a given twist
level is:
TM = TPI / √ Ne

The twist factor is also named twist multiplier in some
countries.

8. Twist &Twist Multipliers

The threshold between weaving and knitting yarn has
been determined to be the following twist multipliers:
• Combed cotton yarn αe = 3.7
• Carded cotton yarn αe = 3.9

Yarns with twist multipliers below these values have
been classified as knitting yarns.

This is the standard adopted by Uster

9. Twist &Twist Multipliers

The cloths were woven from the 10s cotton
yarn.
( W – Warp, F – Filling, and the TM)

11. Twist Direction

12. Twist Direction

When the yarn is woven or knitted into a fabric, the
direction of twist influences the appearance of fabric and
the hand feel.

14. Twist Direction

Fabric A will be more lustrous than Fabric B, because
light reflected by fibres in the warp and weft is in the
same direction.

Fabric A will be softer while fabric B firmer.

15. Twist Direction & Spirality

Twist direction will also have a great influence on fabric
stability, which may be described by the amount of
skew or "torque" in the fabric.

16. Twist Direction & Spirality

One of the solutions to solve the problem of Spirality is to
coordinate the direction of twist with the direction of
machine rotation.

With other factors
to
give
less
counterclockwise.

Fabrics coming off the needles of a counterclockwise
rotating machine have courses with left-hand skew, and
yarns with Z twist yield right-hand wale skew. Thus, the
two effects offset each other to yield less net skew.

Clockwise rotating machines yield less skew with S twist.
being similar, yarn of Z twist
skew
with
machines
is found
rotating

17. Twist Direction & Strength

No consistent differences in strength for the cloths
made from yarns with S-twist and Z- twists yarn

18. Yarn Twist & Cover Factor

Since thousands of ends or wales are presented side-byside in the woven or the knit fabrics, a slight change in
yarn diameter can result in a substantial change in the
overall cover factor of fabric.

Differences in yarn twist lead to deviations in yarn
diameter. A reduction is yarn twist increases the yarn
diameter and decreases the density

The yarns with low twist numbers are bulkier and softer,
the fabric produced has a higher cover factor and softer
hand.

19. Yarn Twist & Cover Factor

Knit fabric strength is depends upon yarn strength and
stitch (loop) length.

20. Yarn Twist & Cover Factor

Higher TPI yarn is more rigid and have higher resistance
to bending while loop forming in knitting, than Low twist
yarn; hence, the radius of their curvature is longer.
Hence, we can not have small loop length.

An optimum combination of strength and flexibility can
be achieved through many options including a proper
level of twist.

21. Twist & Elongation

Increasing twist factor will leads to an increase of yarn
elongation, which in turn the increase of the knitted
fabrics elongation.

Good elongation values in the yarn will reduce fabric
holes.

Also, the increased twist fabric causes the increase in
seam elongation

22. Yarn Hairiness

The reduction of twist increases the hairiness
because the number of protruding fibers
increases.

Consequently the pilling tendency is also
affected.

23. The effects of loop length and yarn twist
factors on seam performance

Seam elongation was positively affected by loop length
and yarn twist factor.

By contrast, seam strength and seam efficiency were
negatively affected by loop length and yarn twist factors .

i.e. As the loop length and yarn twist factor increases,
seam strength and efficiency decreases.

Increasing yarn twist factor will increase the strength of
constituent yarns, which in turn increases the knitted
fabric strength. Thus, the increased twist factor will lower
seam efficiency.

24. Yarn twist CV%

In handling large quantities of data statistically, the
coefficient of variation (C.V.%) is commonly used to
define variability and is thus well-suited to the
problem of expressing twist variation.

It is currently probably the most widely accepted
way of quantifying irregularity.

It is given by :
coefficient variation (C.V.%) =
(standard deviation/average) x 100

25. Yarn twist CV%

The variation of yarn twist CV should not exceed 3.5% to
avoid quality problems which can be recognized by the
human eye.

26. Yarn twist for a specific end use

Alpha e is for English count

27. Summary

Cotton spun yarns for knitting should exhibit good hand
or softness, therefore need less twist.

This lower twist leads to softer yarn and fabric.

Yarn Torque or liveliness should be at a minimum to help
prevent excessive fabric shrinkage, skew, and torque.

28. Summary

The formation of spirality may be prevented by
various yarn-related methods.

Some of these methods include :
a) low-twist-lively yarns;
b) balanced plied yarns can be preferred,
c) and S-twist and Z-twist single yarns are
used at alternate feeders, respectively

29. Yarn Twist
We will discuss other parameters in next edition.
Until then,
Bye Bye.
Note:
This is a Training material prepared for internal
training purpose.