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 are formed by a single end twisted with a certain number of turns per meter: plied yarns, when they are formed by two or more ends twisted together in the opposite direction to the first twist.

Highly twisted yarns are used for warps, lightly twisted yarns for wefts, and medium-twist yarns for knitting.

Below I describe the various types of yarn twists and designs:

• Single: Yarn formed by discontinuous fibers joined by twisting. Thread formed by 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 ends joined together without twisting – Simple plied: Thread obtained by plying two ends of equal count. The plying twist is in the opposite direction to that of the single ends.
• Complex plied: Thread obtained by plying two or more ends of simple plied threads. Each plying operation must have a twist direction opposite to that of the threads being joined together.
• Corded: Thread obtained by plying two or more ends 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 is wound with a slight overfeed.
  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 with a twist direction opposite to that of the effect thread. The effect thread has a slight overfeed. The final appearance is a granular and crimped surface, characterized by the presence of marked and dense undulations.
• Bouclé: Consists of at least 3 components, like Frisé yarn. The effect thread is characterized by strong overfeed, which leads to the superficial formation of evident loops.
• Vrillè: 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 ends of different colors, twisted together.
• Jaspé: Consists of 3 ends of different colors and sometimes different counts, twisted together.
• Slub: Characterized by thickenings in diameter, present at regular intervals, having variable length and thickness, very similar to the irregularities of the yarn called “slubs”.
• Neps: Characterized by the superficial presence of spherical accumulations of colored fibers or “neps”, having various colors.
• Chenille: Consists of 2 threads twisted together, which clamp a third thread, the effect thread, overfed in such a way as 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 high bulk and a “velvety” surface to the thread.
• Spiral Covered: Consists of a core thread, usually elastic, around which one or more threads of different natures are wound using various systems.

The uniformity of thickness can be appreciated by winding the thread over a cardboard of a different color from the thread itself. The eye, preferably through a magnifying glass, appreciates any differences in thickness.

Tenacity, i.e., mechanical resistance, is determined with instruments called dynamometers, which also provide the elongation of the yarn before breaking and thus its elasticity.