Introduction
In textile production, yarns have to be identified by size so different materials can be compared and used correctly. That is why measurement standards were established for cotton-type yarns, wool-type yarns, and filament yarns. The range of systems can look unnecessarily complicated, but most of them developed from measurements that were suited to local manufacturing needs and may go back for hundreds of years. The present trend is toward metric measurements, yet traditional terminology is still widely used. The main point to keep in mind is simple: yarn measurement varies by fiber type, by yarn form, and by whether the system measures size directly or indirectly.
Yarn Size and Yarn Number
Yarn size or fineness is referred to as yarn number. For filament yarns, it is expressed in terms of weight per unit length. For spun yarns, it is expressed in terms of length per unit weight. The defined weights and lengths differ with fiber type, so the same idea does not always use the same scale. Finer yarns are often an indication of better quality, but they may not be as durable as slightly coarser yarns. Examples that show the relationship between yarn size and fabric weight also help make the point.
Direct Numbering Systems
Tex, Denier, and Decitex
Direct methods of measurement rely on fixed lengths of yarn. A specified length of yarn is measured, and that length is then weighed. The measurements used are tex or denier. As explained earlier, tex is the weight in grams of a 1-kilometer (1,000-meter) length of yarn, and denier is the weight in grams of 9,000 meters of yarn. In all these measurements, the higher the number, the coarser the yarn.
Denier Per Filament and End Use
The size of filament yarns may be designated by giving the denier or tex of the total yarn or by the denier per filament (dpf). This last measure, together with the number of filaments, provides extra information about the yarn. Denier describes yarn size using filament fibers. The term is used for both smooth- and bulky-textured yarns. The size of filament yarns is based on both the size of the individual fibers in the yarn and the number of fibers grouped into the yarn. For both fibers and yarns, denier is the weight in grams of 9,000 meters. In this system, the unit of length remains constant. The numbering system is direct, also called a fixed-length system, because the finer the yarn, the smaller the number.
Yarn denier is often used to describe filament yarn fabrics because it gives additional information to fabric specialists. Higher numbers describe larger yarns. For example, a 160-denier fabric has finer yarns than a 330-denier fabric. The 160-denier fabric will be softer and more comfortable in contact with the skin and less durable than the 330-denier fabric. However, the 330-denier fabric would produce a more durable product, such as luggage.
When denier is listed as a fraction, the first number describes the size of the yarn and the second describes the number of filament fibers in the yarn. When individual fiber size is important, it can be determined by dividing the first number by the second number. For example, a technical nylon fabric is described as 1,000/280. The yarn is a 1,000-denier yarn and there are 280 filament fibers present in it. Each fiber is approximately 3.6 denier in size. This would be a relatively tough, durable, and stiff fabric for such end uses as upholstery, soft luggage, or tool pouches. This method of describing yarn denier and number of filaments is used for all types of fabrics made of filament yarns, including microfiber yarns used in apparel and interior textiles.
Tex and Decitex in Metric Measurement
The International Organization for Standardization has adopted the tex system, which determines yarn count or number in the same way for all yarns. Tex is the weight in grams of 1,000 meters of yarn. One tex is equal to 0.11 denier (tex = denier/9). Because the size can be small, the term decitex (dtex) may be used. One dtex is 10 times larger than one tex.
Indirect Numbering Systems
Cotton Count and Related Indirect Systems
Indirect methods of yarn numbering rely on fixed weights of yarn. Each system establishes a number of hanks (skeins) of yarn that make up either a pound or a kilogram of yarn weight. Pounds are used for measurements in the English system and kilograms for measurements in the metric system. The cotton system is discussed here, since many yarns are numbered by the cotton system. It is an indirect or fixed-weight system: the finer the yarn, the larger the number. Thus, a fine yarn would be a 70 and a coarser yarn would be a 20. The yarn number, or cotton count, is based on the number of hanks of 840 yards in 1 pound of yarn.
The size of the hanks used differs for the different natural fibers, with the measures being as follows: cotton count equals the number of hanks of 840 yards in 1 pound; linen count, also called linen lea, equals the number of hanks of 300 yards in 1 pound; woolen count equals the number of hanks of 1,600 yards per pound; worsted count equals the number of hanks of 560 yards per pound. The woolen/worsted and tow/line systems are similar, except that the length of yarn in a hank differs with each system. Finer yarns are often an indication of better quality, but they may not be as durable as slightly coarser yarns. Examples that show the relationship between yarn size and fabric weight also help make the point.
Ne, Nm, and Comparison Between Systems
All these yarn numbers are reported in the technical or research literature followed by the abbreviation Ne, which stands for “number in the English system.” Metric yarn numbers in the indirect measurement system equal the number of 1,000-meter hanks in each kilogram, and this measurement is followed by the abbreviation Nm, which stands for “number in the metric system.”
Because different lengths of yarn are used to establish yarn numbers in the varying systems, yarn numbers are not directly comparable. Looking across the comparisons, one can see that depending on the system being used, comparably sized yarns can have widely different numbers assigned. Nevertheless, regardless of the specific yarn numbers, certain basic principles apply. In the direct system, the lower numbers indicate finer yarns, and higher numbers indicate coarser yarns. Just the opposite is true in the indirect system, where higher numbers indicate finer yarns and lower numbers coarser yarns. For example, if 7 hanks of one linen yarn weigh 1 pound, and 50 hanks of another linen yarn weigh 1 pound, obviously the yarn with the higher number (50) would be finer than the yarn with the lower number (7).
Conclusion
As textile standards continue to move toward metric measurements, yarn count still depends on knowing which system is being used. Tex, denier, and decitex describe yarn by fixed length, while cotton count, linen count, woolen count, worsted count, Ne, and Nm describe yarn by fixed weight. The direction of the scale matters too, since direct systems use lower numbers for finer yarns and indirect systems do the opposite. Yarn regularity adds another layer, because regular yarns, novelty yarns, and composite yarns do not appear or behave the same way. With these basics clear, yarn count becomes much easier to read, and that knowledge will remain useful as textile terminology keeps balancing metric and traditional practice.
