yarn technical terms

1. Count

Count is a measure of the fineness of yarn.

Ne: English Count

In new English system (Ne) count of yarn is expressed as number of hanks of 840 yards in one pound.

Tex = 1g/km =1mg/m

Nm = The determination of the proportion of length to weight

e.g. Nm 85 = 85 km of this yarn weigh 1'000 g

1.1 Definition of the relative count - Count C.V.

The relative count gives the mass deviation in % of the whole test length of each test sample as compared to the average mass of all samples. This value is an indication of relative count deviation (CV).

The lower the value the better.

The variation of the yarn count (CV count) is the variation from one bobbin to the other. If this variation is more than 2% the difference in the fabric is visible with bare eyes.

2. C.V%

A statistical measure of the variation of the individual readings (Coefficient of observed variation). In general the lower the C.V.% the better is the measured value of the yarn.

3. Twist

Twist Direction

The Twist direction is a pitch direction of the fibre in the yarn in a screw line, it can be in Z or in S direction.


Single fibres in the yarn and the yarns in the ply yarn, hold vertical, lie in direction of the letter Z.


Single fibres in the yarn and the yarn in the ply yarn lie in a thread, hold vertical, in direction if the letter S.

Twist per meter

This value is only measured over one inch (1inch=2.45cm). This term is used commonly to express twist level of the yarn.

4. Imperfections

Imperfections is the description for thin, thick places and neps in 1000m of yarn.

4.1 Thin places

Thin places are places in the yarn, that are thinner than -50% or more than the average diameter of the yarn. There is no limitation in the length of the thin place. The less you find thin places in the yarn the better is it.

4.2 Thick places

Thick places are determined where the yarn diameter is in excess of 50% of the average yarn diameter and the length is 8-12 mm.

4.3 Neps

It has to be made a differentiation in the two faults - thick places and neps.

Frequently-occurring thick places exhibit a length that corresponds with the mean staple length of the fibre. A nep is a very short thick place in the yarn, a small fault having a length of 2mm diameter of 3 times or more at a standard setting of 200%. It can either be a fiber nep, a seed coat nep or a trash particle. It can be thicker than +200% of the average yarn diameter. The increase for neps is calculated to a reference length of 1mm. They can be a bunch of entangled fibres commonly not bigger than pin ball head.

The less imperfections in the yarn, the better the appearance of the fabric.

5. Uster %

This is a measure of unevenness of sliver/roving/yarn - Uster% is a measure of variation in weight (in gms) of approximately 1 cm.

Note: The value is better, the lower it is.

5.1 Uster Eveness in %

This is a measure of variation of imperfections in the yarn. The lower the value the better the yarn, because less imperfections exist in the yarn.

6. Degree of Hairiness

Definition of hairiness value H

The hairiness value informs about the count of fibres protruding from the yarn base. The hairiness H measurement unit of the Uster Tester examines the hairiness of approximately 1cm lengths of yarn. It is specified as the average value of hairiness over the total test length.

e.g. Hairiness 3.5 = at a yarn length of 1cm, generally 3.5 cm fibres desist from the yarn.

Use: the lower the hairiness, the lower the fibres get stuck and the lower the fluff = better running characteristics.

Hairiness variation may affect the further usage of the yarn. But a high hairiness can be useful for particular end products and may actually be desirable.

• The higher the numerical hairiness value H the hairier the yarn.

• The lower the CV value of hairiness the better.

6.1 Variation of hairiness sH

The standard deviation sH is a measure for the variation of the yarn hairiness. It is relative to a measurement field of 1cm. The use of the ‘sH’ value is to determine whether any significant hairiness variation is present in the yarn thus the hairiness can vary quite strongly with in a batch. The smallest possible hairiness variation should be the desired goal.

Influence of yarn count on the hairiness:

The larger the number of fibres in the cross–section of the yarn, and with constant twist, the larger also the number of protruding fibres. A coarse yarn therefore has a higher hairiness than a fine yarn.

7. Breaking Force (Single yarn strength)

This is the force required to break a strand of single yarn. It is expressing Centi-Newton (cN). In a certain degree, the higher the value the better the yarn – 18-20cN/tex would be the best value range for yarn Puma uses. Normally, the ideal value must be determined for a wide range of different yarn counts. For a narrow range the values do not change radically.

8. R.K.M

This can be expressed by the “Length of yarn in km” at which yarn will break of its own weight”. This is equivalent to breaking load in g/tex.

RKM is the short expression for “Reisskilometer” – “Breaking-kilometer”, which is an unit out of date.

E.g.: a Cotton-yarn with 15 RKM means, it would break of its own weight, if you wind off 15 km of the yarn and hang it up in 15km.

Nowadays it is common practice, to use the unit Centi-Newton per Tex (cN/Tex) or gram-force per Tex (gf/Tex). RKM and cN/Tex or gf/Tex are practically the same.

Note: The coarser the yarn, the higher the value should be.

9. Strength (Tenacity):

The Tensile Strength expressed as force per unit liner density is called tenacity. This is normally expressed as gram force per tex (gf/tex).

Note: The higher the value, the better the strength of the yarn.

10.Elongation in %

Is the measure of the extent of deformation along the axis of a material under a tensile stress expressed as a percentage change in length based on original length of Test Sample. The percentage of length up to which the yarn can be extended before the occurrence of yarn breakage.

It is the elasticity of the yarn in % , e.g. 5.8 % = you can stretch the yarn to 5.8 % until it breaks.

Use: The higher the breaking energy, the more you can strain the yarn = better running characteristics.

The value depends on the specifications of the yarn supplier or what the customer requests. In general a higher elongation is better for knitting and yarn quality.

11. Count Strength Product (CSP)

CSP I is an old Strength value, which is not used in several countries anymore.

It is a number which is derived by multiplication of count & lea strength(in lbs.):

Note: The higher the value the better the yarn.

Lea: In one lea 120 yards length of yarn is wound by 80 wraps. Each wrap has a length (circumference) of 1.5 yards.

Lea strength: This is breaking load required to rupture one lea. It is generally expressed in pound.

Note: The higher the value the better the yarn.

12. Classimat fault

There are 23 types of random faults categorized on the basis of size by Uster Classimat system.

It is the sum of tested yarn values. The spinner determines the values to a specific amount and range, in which the yarn tests must match.

13.Uniformity Ratio%

2.5% Span length

Distance 2.5% of the fibers extend from the clamp where they are caught at random along their length.

50% Span length

Distance 50% of the fibers extend from the clamp where they are caught at random along their length.

Uniformity Ratio%

The ratio of 50% span length to 2.5% span length expressed as a percentage.

U.R. % =

50% span length x 100


2.5% span length

14. Short Fiber Index (SFI)

This is an estimate of the Short Fiber Content in the cotton. The percent by weight of fibers less than 0.5 inch is usually referred to as the Short Fiber Content.

15. Micronaire (Mic.) - fineness

A measure of mass per unit length expressed in micrograms per inch for cotton.

A fiber sample of constant weight is measured by passing air through the fibers and measuring the drop in pressure. The micronaire scale has been established empirically with a standard set of cottons and is not linear. Other factors such as fineness and maturity have an influence on micronaire results.

16. Grades and Classes for Cotton Fibre


A small knot of tangled fibre.


An industrial yarn preparation. During the combing process, fibres are combed to make them parallel in the sliver and short fibres are removed

Yarn Imperfections: Refers to yarn defects that usually either cause thick or thin places in the thread that can cause sewing problems. Some of these yarn imperfections include: knots, slubs, neps, dropped ply, dropped filament, singles kinks, etc.

Yarn Size: Yarn size is equal to the equivalent size times the number of ply (20/1 equivalent size = 40/2 or 60/3 yarn size). The cotton count system is used on most spun and corespun sewing threads. This is an indirect numbering system where the larger the number, the smaller the size. (45/2 is finer than a 28/2 yarn size).