Yarn twisting

The fundamental characteristics of yarns are:

• twist
• thickness uniformity,
• tenacity and elongation,
• count

The twist of yarns is determined with twist testers. The twist can be right (called Z-twist) or left (called S-twist). Yarns are called single when they consist of a single strand twisted with a certain number of turns per meter: plied yarns when they consist of two or more strands twisted together in the opposite direction to the first twist. Highly twisted yarns are used for warps, loosely twisted ones for wefts, and medium-twist yarns for knitting. Below, I describe the various types of twists and fancy yarns:

• Single: Yarn made from discontinuous fibers joined by twisting. Thread made from continuous fibers joined with or without twisting. If the thread consists of a single fiber, it is called a monofilament.
• Doubled: Thread composed of one or more strands joined together without twisting - Simple plied: Thread obtained by twisting two strands of the same count. The plying twist is in the opposite direction to that of the single strands.
• Complex plied: Thread obtained by twisting two or more strands of simple plied threads. Each plying operation must have a twist direction opposite to that of the threads being joined.
• Cord: Thread obtained by twisting two or more strands joined together with the same twist direction as the single threads.
• Ondé: Consists of a main thread, called the core, around which a second thread with slight overfeeding is wound. The final effect is a surface with limited and regular undulations.
• Frisé: Consists of 3 components: a core thread around which an effect thread and a binding thread are twisted. The binding thread is twisted in the opposite direction to the effect thread. The effect thread has slight overfeeding. The final appearance is a grainy and crimped surface, characterized by the presence of marked and dense undulations.
• Bouclé: Consists of at least 3 components, like Frisè yarn. The effect yarn is characterized by strong overfeeding, which leads to the surface formation of evident loops.
• Vrillé: Consists of 2 components like Ondé yarn. The effect thread has a high degree of twist, so much so that the surface loops tend to twist on their own axis, forming small curls.
• Mouliné: Consists of 2 or more strands of different colors, twisted together.
• Jaspé: Consists of 3 strands of different colors and sometimes different counts, twisted together.
• Slub: Characterized by diameter thickenings, present at regular intervals, with variable length and thickness, very similar to the irregularities of the yarn called "slubs".
• Nèp: Characterized by the surface presence of spherical accumulations of colored fibers or "nèps," having various colorations.
• Chenille: Consists of 2 threads twisted together, which clamp a third, effect thread, overfed to form loops that protrude from the body of the thread. The effect thread has high bulk. A special operation cuts the end part of the loops, allowing the thread to fray. In this way, many tufts of fibers appear on the surface, giving the thread high bulk and a "velvety" surface.
• Spiral Covered: Consists of a core thread, usually elastic, around which one or more threads of different natures are wound using various systems.

Thickness uniformity can be assessed by winding the thread onto a cardboard of a different color from the thread itself. The eye, preferably through a magnifying glass, will appreciate any differences in thickness. Tenacity, or mechanical strength, is determined with instruments called dynamometers, which also provide the yarn's elongation before breaking and thus its elasticity.