The Yarn Quality Index

What Is the Yarn Quality Index?

Yarn, whether it’s used by a hobbyist, or in manufacturing, is an important component in determining the quality of a fabric. The yarn quality index is a standardized system for evaluating the structure of yarn and thread.

On the yarn quality index, four properties of fiber are taken into consideration, they include:

  • Yarn fineness, or yarn count and yarn density contribute to quality. Yarn fineness refers to the thickness of a yarn. Thickness can’t be measured with a tape measure so it is determined in wraps per inch or yarn count. To determine yarn count, the yarn is wrapped around a rod then the wraps are counted to the inch.  Yarn density refers to the weight of the yarn.
  • Twist and direction of the twist determines strength. Yarn is made by spinning raw fiber into one continuous strand, this is called a single. Often two or more singles are spun together or plied this increases the strength of the yarn. The degree of twist determines the strength of the yarn. The tighter the twist the stronger the fiber. 
  • Single yarn strength is also called yarn fastness. A weak yarn will compromise the integrity of the finished item. A strong yarn will not break when it is knitted or woven into fabric. 
  • Appearance quality of yarn. Yarn is visually inspected for areas of thinness, slubs, or unevenness in color.

This index is not an absolute determination of quality. The very characteristics that are considered low quality can make some yarns desirable. There is no good or bad yarn

Who Uses the Yarn Quality Index and How?

Manufacturers of yarn and textiles use the quality index. They employ a variety of scientific tests that have been constructed by the ASTM to ensure quality. To ensure consistency of outcomes, the tests are performed on machines.

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