Linear Density (Yarn Count)
The thickness or diameter of a yarn is one of its most fundamental properties. However, it is not possible to measure the diameter of a yarn in any meaningful way. This is because the diameter of a yarn changes quite markedly as it is compressed.
Yarn is a soft assembly of fibres. There are voids spaces between the fibres within yarn. (Most methods of measuring the diameter of yarn involve compressing the yarn and hence the measured diameter changes with the pressure used. So mechanical means, devices cant be used for measuring the diameter of the yarn.) Yarn is thinner at twisted places and thicker where twist is less. Yarn appears vivid because of the hairiness; it has protruding fibres upon its surface and also sometimes loops of fibers (kinks). (Due to undefined boundaries, optical methods e.g. microscope cant be used to measure yarn diameter). Also there are lots of differences in the structure and cross section of different fibres.
- Wool has nearly round cross-section
- Silk has a triangular cross-section
- Cotton is like flattened tube
- Man-made fibres are often made with trilobal (nylon), star or hollow cross-section for particular purposes.
