Denim Manufacturing: Yarn Processes

Welcome to the Yarn Processes course where you will learn about “Yarn Numbering”, “Yarn Spinning Systems”, “Warping”, “Dyeing”, and “Slashing”.

Yarn Numbering

Yarns used in denim fabrics are termed “short-staple spun yarns,” because they are formed from fibers having a staple length of less than 2.5 inches. The cotton fiber usually is just over an inch long. One of the key pieces of yarn information for development and manufacture of denim is the choice of yarn size. The terms “yarn number,” “yarn count,” and “yarn size” are used interchangeably to refer to the linear density of a given yarn.

Yarn Spinning Systems

The two most common spinning systems used to produce yarns for denim fabrics are ring spinning and open-end rotor spinning.


“Warping” is the process of transferring multiple yarns, each on a separate yarn package, onto a single collecting package.


Most denim fabric is yarn dyed; the warp yarns are dyed with indigo, and the filling yarns are left undyed. However, solid shades are becoming more popular and can be dyed by various methods.


The main purpose of sizing warp yarns is to encapsulate the yarn with a protective coating. This protective coating reduces yarn abrasion during weaving. The size also reduces yarn hairiness, preventing adjacent yarns from becoming entangled. For many years, native or slightly modified starches with corresponding binders were regarded as the most economical size for indigo warps. The change to garment-washed denim led to the development of new sizing recipes. The type and quantity of size used depends on what finishing operations will be used and whether the product is loomstate or mill-finished denim.