Yarn Count/Linear Density | Determination of Yarn Count

The thickness or diameter of a yarn is one of its most fundamental properties. However, it is not possible to measure the diameter of a yarn in any meaningful way. This is because the diameter of a yarn changes quite markedly as it is compressed. Most methods of measuring the diameter of yarn, apart from optical ones, involve compressing the yarn as part of the measurement process. Therefore the measured diameter changes with the pressure used so that there is a need for agreement on the value of pressure at which the yarn diameter is to be defined. On the other hand optical systems of measuring yarn diameter have the problem of defining where the outer edge of the yarn lies as the surface can be rather fuzzy, having many hairs sticking out from it.

Therefore the positioning of the yarn boundaries is subject to operator interpretation. Because of these problems a system of denoting the fineness of a yarn by weighing a known length of it has evolved. This quantity is known as the linear density and it can be measured with a high degree of accuracy if a sufficient length of yarn is used. There are two systems of linear density designation in use: the direct and the indirect.

Direct System

The direct system of denoting linear density is based on measuring the weight per unit length of a yarn. The main systems in use are:

• Tex - weight in grams of 1000 metres
• Decitex - weight in grams of 10,000 metres
• Denier - weight in grams of 9000 metres
1 tex = 10 decitex.

Tex is the preferred SI unit for linear density but it is not yet in common use throughout the textile industry. Other direct systems can be converted into tex by multiplying by the appropriate factor. In the direct system the finer the yarn, the lower is the linear density.

Indirect System

The indirect system is based upon the length per unit weight of a yarn and is usually known as count because it is based on the number of hanks of a certain length which are needed to make up a fixed weight. This is the traditional system of yarn linear density measurement and each branch of the industry has its own system based on the traditional length of hank associated with the locality and the type of yarn manufactured.

The main English ones which are still used every day in the relevant parts of the industry are:

• Yorkshire Skeins Woollen Ny

Count = number of hanks all 256 yards long in 1 pound

• Worsted Count New

Count = number of hanks all 560 yards long in 1 pound

• Cotton Count Nec

Count = number of hanks all 840 yards long in 1 pound

• Metric count Nm

Count = number of kilometre lengths per kilogram

In the indirect systems the finer the yarn, the higher the count. One way of measuring count is to measure the linear density using the tex system in the first instance and then to convert the result to theappropriate count system using the appropriate conversion factor K .

Count =K/Tex 
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Mazharul Islam Kiron is a textile consultant and researcher on online business promotion. He is working with one European textile machinery company as a country agent. He is also a contributor of Wikipedia.

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