This International Standard specifies a method for the determination of the direction of twist in yarns, the amount of twist in terms of turns per unit length and change in length on untwisting, by the direct counting method.

NOTE -- Determinations based on the untwist-twist procedure are not recommended since they may reflect appreciable errors under some conditions due to a lack of knowledge of the proper tensions to use. However, the untwist-twist procedure is sometimes preferred for spun yarns, but its use should be the result of prior agreement between the parties concerned.

This method is applicable to

a) single yarns (spun or multifilament);
b) folded (plied) yarns;
c) cabled yarns.

Separate procedures are given for each type of yarn. The method is designed primarily for yarns in packages, but with special precautions the procedures can be used for yarns taken from fabrics. It is not suitable for the determination of twist in a monofilament.

This method is not applicable, except by agreement, to yarns which stretch more than 0.5% when the tension increases from 0.5 to 1.0 centinewtons per unit linear density of the yarn in tex. Such yarns may be tested under special conditions of tension which are accepted by all parties interested in the test results.

This method is not suitable for products of open-end spinning.

This method is not applicable to yarns which are too large to permit of their being placed in the clamps of testing apparatus without crushing or distortion severe enough to affect the test results.

The method covers the determination of twist in plied and cabled yarns as follows:

In plied yarns - the final twist of the plied yarns and the original twist of the single yarn before plying.

In cabled yarns --

a) the final cabling twist of the yarn;

b) the original twist of the plied yarn after plying, but pior to the last stage of processing;

c) the twist of the single yarn before plying.

If desired, the twist of the single and plied yarn components as they lie in the final structure may be determined by the special procedure given in 10.5.7.

Time-dated standard