The three primary dimensions to carpet are:
Gauge (Width), Stitch rate (Length) and Pile height (Height).
- GAUGE is the distance between the needles. For example, 1/8 gauge simply means there is 1/8 inch between each needle, or there are 8 needles per inch.
- STITCH RATE (or stitches per inch) defines the number of times per inch a stitch occurs, just as gauge expresses the frequency of tufts across the width. Stitch rate is the number of times an individual needle inserts a tuft into the primary backing as the primary backing moves one inch through the tufting machine. This is sometimes abbreviated SPI. Therefore, 8 stitches per inch means that as the primary backing moved through the tufting machine, a single needle form 8 tufts or stitches.
- PILE HEIGHT is the length (expressed in decimal parts of one inch) of the tuft from the primary backing to the tip. All other factors being equal, a carpet with a higher pile height will possess more yarn on the wearing surface and will essentially be more durable.
Other common measurements are:
- DENIER or YARN DENIER: Unit of weight for the size of a single filament or yarn bundle. The higher the denier, the heavier (coarser) the yarn and the more resilience it will offer. Denier is expressed as the weight in grams of 9,000 meters of yarn. 9,000 meters of an 18 DPF (denier per filament) would weigh 18 grams and 9,000 meters of a 1230/2-ply yarn would weigh 2,460 grams. The higher the DPF, the greater the fiber’s resilience and its resistance to bending, but also the harsher it feels to the hand. DuPont Tactesse® has a denier of 12, which gives it a softer feel than the 15-18 denier more commonly used in carpet fibers.
- DENSITY or PILE DENSITY: The weight of a pile yarn (including buried portions of the pile yarn) in a unit volume of carpet, which is expressed in ounces per cubic yard. Also called “Average pile yarn weight”. The closer the tufts are to each other, the denser the pile and the less weight each individual tuft has to support. Pile density is not only evaluated by the closeness of the tufts but also by the height and weight of the pile yarn. All other things being equal, the greater the pile density, the greater the wearability of the carpet and the longer it will last.
- FACE or PILE WEIGHT: The total weight of the face (above and below the backing) yarns in the carpet. The more ounces per square yard, the denser the pile and, potentially, the greater the wearability of the carpet.
- TWIST: Twist is the process whereby two or more spun yarns are twisted together. Twist is counted by the number of turns per inch (TPI) of the yarn. The performance of cut pile carpet is highly dependent on the rate of twist and twist retention. Heat setting helps stabilize yarn twist by subjecting the yarn to high temperature steam under pressure. Most carpet yarns have 2.5 to 6.0 twists per inch. A higher twist level usually results in better texture retention and better resilience. A high twist will result in a frieze, a medium twist will produce a Saxony, and low twist will result in a velour or Saxony plush style.
- TUFT BIND: Loop pile styles have closed loops, so twist is not a major factor. Rather, tuft bind is a consideration. Tuft bind is the relative strength of the attachment of the yarn loops to the backing of the carpet.
- STAPLE YARN SIZE: The size of staple yarns is most often expressed in what is known as the cotton count system. In this system, a yarn count is an inverse system; i.e., the larger the numerator, the smaller the yarn, and is based on the number of 840 yard hanks required to weight 1 pound. For example, a 1 cotton count (cc) yarn has 1 hank per 840 yards, while a 2.5 cc yarn would require 2.5 hanks (2100 yards) to weigh 1 pound. The denominator represents the ply count of the yarn.
Related Carpet Manufacture and Fiber Chemistry Information:
- Carpet and Rug Fiber Chemistry
- Carpet Dyeing by the Mill or Fiber Producer
- Carpet Fiber Identification
- Carpet Fibers
- Carpet Manufacturing
- Fibers - An Overview
- Nylon Type 6 versus Type 6,6
- Olefin Carpet Fiber
- Polyester Carpet Fiber
- Primary Backing
Related Carpet Manufacture and Fiber Chemistry Products:
- Carpet Fibers and Manufacture 2-hour Video by Bane-Clene’s Chemist
- Oriental and Area Rug Construction and Maintenance Training DVD by Bane-Clene’s Chemist
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