Yarn numbering is a term used to describe a yarn’s physical size or, more specifically, its linear density. Since short-staple spun yarns, like those containing cotton, can vary greatly in their bulk, measuring a yarn’s diameter, in a consistent way, can be almost impossible. For this reason, it is necessary to employ a more precise way of describing a yarn’s physical size.
There are two main methods for assigning a yarn number. One method is called the direct yarn numbering system. In this method, the yarn’s linear density is denoted as a weight to length ratio. This method is commonly used for synthetic or man-made fiber.
For example, a 70 denier yarn means that there are 70 grams per 9000 meters. Denier is just one of the direct yarn numbering units but it is one of the more common direct units used for synthetics. Here are some others:
Direct yarn numbering system:
- Decitex = weight in grams/ 10,000m
- Tex = weight in grams/1,000m
- Denier = weight in grams/9,000m
The other method for describing a yarn’s linear density is called the indirect method. In this method, the yarn’s size is described in length to weight units. For cotton yarn, it is typical to see the denotations Ncc or sometimes Ne. These denotations are otherwise known as cotton count or number English. For example, a Ne 30/1 100% cotton or blend. Yarn means 30 times 840 yards per pound. 840 yards is known as a hank. There are also some other indirect units.
- Worsted Count = number of 560 yard lengths / Pound
- Woolen Run = number of 1600 yard lengths / Pound
- Woolen Cut = number of 300 yard lengths / Pound
- Number Metric (Nm) = number of 1000 meter lengths / Kilogram
With all this said it is important to realize that there are other yarn numbering units that may be encountered. It is impossible to cover all of them. This is especially true in China and some other foreign countries where many variations of yarn numbering may have evolved. Be aware that not everyone speaks or even knows all of these terms and their relationships.
No matter the spinning system employed, all yarns contain twist to hold the fibers together. The frictional forces created by the twist are the means by which all yarns are held together. Most single yarns will be produced with a “Z” twist. That means the helix angel is the “Z” direction. Sometimes “S” yarns will be produced for special technical reasons. An “S” twist yarn’s helix angle is in the “S” direction. Because of its mechanical design, yarns produced on the OE system will always be “Z” twist yarns. Both ring and air-jet spinning systems can be set up to produce an “S” twist when it is required.
Twist Multiple (TM) is a common way of designating how much twist a yarn contains. TM is a relationship between yarn number (or count) and the turns per inch in the yarn. Using number English or cotton count, that relationship is represented as follows: TM = TPI√ Ne.
Where TM is twist multiple, TPI is turns per inch, and Ne is number English (or cotton count). Twist level may also be expressed in other ways, such as turns per meter. When communications between parties involve twist, it’s important to know the terms and units being used.
All yarns are originally spun as single yarns, but for certain end uses, single yarns may be twisted together to produce a ply yarn. Most common are two-ply yarns, formed by twisting two single yarns together. The plying twist is in the opposite direction of the singles twist. That means most ply yarns will contain an “S” twist.
Ply yarns are used where extra strength and evenness are required.