Slub fabric is fabric that has retained thread imperfections, such as lumps or knots, which may have occurred during the thread weaving process. Traditionally, slub fabric was believed to be defective and poor in quality, however, designers of contemporary clothing have begun to use slub fabrics due to their recent aesthetic appeal.
During the early 19th century, the term slub referred to the preparation process that wool underwent before it was spun, in which tailors would twist, or slub, the wool. This twisting would create threads of wool yarn that were different in degrees of thickness. The different thicknesses would make the fabric appear uneven when the wool was sewed together to make a garment. Sometimes, the different threads would cause knots and bumps to form as well.
Modern day slub fabric is not isolated to just wool. Fabrics such as silks and linens are used to make slub fabric as well. Some modern slub fabrics include butcher cloth, butcher linen, crash, Donegal tweed, Doupioni silk, pongee, shantung, silk noil, Thai silk and tussah. The process for creating silk slub fabrics is different from wool slub fabrics.
The silk fabrics obtain their slub features due to the difficulty of spinning the silk from the double silk worm cocoon. The insect wraps the silk so tightly that it is almost impossible to untangle completely, creating slub imperfections in the fabric.