Denier Measurement

Grams per 9000 Meters, From a Strand of Silk

Denier is a measuring system built for materials too fine to weigh conveniently in short lengths. The denier value is defined as the mass in grams per 9000 meters of yarn, so a yarn's denier is found, in practice, by weighing a manageable sample: generally a sample of 900 meters is weighed and the result is multiplied by ten to obtain the denier weight, because measuring a full 9000 meters is both time-consuming and unrealistic. The system is based on a natural reference: a single strand of silk is approximately one denier, since a 9000-meter strand of silk weighs about one gram. From that anchor the whole scale follows: 1 denier = 1 g / 9000 m = 0.11 mg/m. The term denier comes from the French denier, a coin of small value, and applied to yarn a denier was held to be equal in weight to 1/24 ounce (1.2 g). The unit is not mostly obsolete, as is sometimes claimed, but still finds much use in the fiber industry, because it states fineness directly for the filaments the industry actually buys and spins.

The most important distinction in using the unit is between a single filament and a whole yarn. There is a difference between filament and total measurements in deniers: the first relates to a single filament of fiber, commonly called denier per filament (DPF), whereas the second relates to a yarn. For straight, uniform filaments the relationship is DPF = total denier / quantity of uniform filaments. That arithmetic explains descriptions that can sound contradictory. A 75-denier yarn is considered fine even if it contains only a few fibers, such as thirty 2.5-denier fibers, but a heavier yarn, such as 150 denier, is considered fine only if its fibers are individually as thin as one denier. Broader terms such as fine may therefore be applied either because the overall yarn is fine or because fibers within the yarn are thin, and a careful specification gives both numbers so fabric makers know the yarn's weight and its filaments' fineness separately.

Microdenier, Microfibers and Opacity in Hosiery

At the fine end of the scale, denier names a whole class of modern fibers. Microdenier describes filaments that weigh less than 1 g per 9000 m, and a fiber is generally considered a microfiber if it is one denier or less. For scale, a one-denier polyester fiber has a diameter of about ten micrometers. Fibers that fine split the work of a yarn among many more filaments, which is why microfiber fabrics feel soft, drape closely and present a smooth surface: the individual filaments bend easily even when the yarn as a whole is substantial. For single fibers, instead of weighing, a machine called a vibroscope is used: a known length of fiber, usually 20 mm, is set to vibrate and its fundamental frequency is measured, allowing the calculation of the mass and thus the linear density, a method suited to samples far too small for the 900-meter weighing routine.

For most shoppers, denier is met on a hosiery packet. In tights and pantyhose, the linear density of yarn used in the manufacturing process determines the opacity of the article in the following categories of commerce: ultra sheer (below 10 denier), sheer (10 to 30 denier), semi-opaque (30 to 40 denier), opaque (40 to 70 denier) and thick opaque (70 denier or higher). The categories work because denier tracks how much fiber is present in a given length, and more fiber per length means more coverage of the leg beneath. A buyer choosing between a 15-denier sheer and a 60-denier opaque is choosing both appearance and durability at once, since finer yarns give a bare-leg look but snag and run more easily, while higher deniers trade some elegance for warmth and wear. Denier therefore operates at both ends of the industry, as an engineering specification for filaments and as the plainest consumer guide to how a pair of tights will look on the leg.