Raw silk filaments straight off the reeling frame are extraordinarily fine – so fine that a single thread from one cocoon would snap under the slightest stress on a loom. Before silk can become the fabric we know, it must go through a transformative process called twisting (also referred to industrially as throwing). Twisting binds multiple filaments into a coherent, loom-ready yarn, and every stage of this process directly decides the strength, feel, and look of the finished textile. Understanding how twisting works – and why each step exists – gives a clear picture of what separates ordinary yarn from premium silk.
Table of Contents
What twisting actually does to silk
A silk cocoon yields a continuous filament stretching anywhere from 600 to 900 metres in usable length, but a single strand is too thin for practical use on its own. Several strands are reeled together first, yet even that combined thread lacks the structural cohesion required for weaving. Twisting solves this problem. A twist is imparted to the raw silk thread through a twisting machine, which increases strength and prevents individual cocoon filaments from splitting apart. The mechanical action of rotating the strands around each other locks the fibres together, distributes tension evenly along the yarn’s length, and compresses the structure into a tighter, more resilient unit.
The amount and direction of twist applied produces yarns with noticeably different characteristics – something silk producers exploit deliberately to create fabrics with distinct textures and performance properties. Torsion is measured in TPM (turns per metre), and depending on the type of yarn being produced, this can range from as low as 300 TPM to as high as 3,000 TPM, allowing producers to emphasise brightness, opacity, softness, creping, or resistance as needed.
The six stages of silk twisting
In professional silk processing, twisting is not a single operation. The complete process is broken into six sequential steps: soaking and drying, winding, doubling, twisting, heat setting, and rewinding. Each step serves a specific purpose, and skipping or poorly executing any one of them affects the quality of every step that follows.
Stage 1: Soaking and drying
The raw silk arrives as hanks – loosely coiled bundles – and must be conditioned before any mechanical processing can begin. Silk hanks are soaked in a mild soap and oil solution (typically 0.5% soap and 2% coconut oil), then semi-dried in shade. The oil softens the fibre and reduces friction during subsequent machine contact, while the moisture makes the silk pliable enough to be unwound without breakage. In some operations, a temporary tint is added at this stage to distinguish warp yarns from weft yarns during the production process – a practical quality-control measure rather than a dyeing step.
It is critical that the soaking solution is properly balanced. The oil used must not damage the silk’s structural properties through alkalinity or rancidity, and the correct mixture is determined by whether the goal is to open the thread’s inner structure or to better fix the subsequent twists. After soaking, the hanks are hung on trolleys and dried slowly to preserve the fibre’s chemical and physical properties.
Stage 2: Winding
Once dry, the silk hanks are transferred to winding machines, where the thread is unwound from the hank and rewound onto bobbins (also called cones or cheeses) in a neat, organised form. This step removes defects such as loose ends, long knots, and gum spots that would interfere with the uniformity of the final yarn. Winding also converts an awkward hank format into a compact, machine-compatible package that feeds smoothly into the doubling and twisting stages. Consistent tension during winding is essential – uneven winding leads to irregular yarn and, ultimately, fabric with visible defects.
Stage 3: Doubling
Doubling is the process of combining two or more single threads into one composite strand. Filaments or threads from two, three, or more bobbins are wound together simultaneously onto a single bobbin, with sensors on modern machines stopping the operation automatically if any one thread breaks. This ensures that the doubled strand contains the exact number of ends required – a key factor in achieving consistent yarn count and strength.
The doubled yarn is not yet twisted at this point; the fibres simply run alongside each other. The doubling process also cleans the yarn from lint and waste, removing weak and thicker sections, so that only uniform material proceeds to the twisting machine. The number of threads combined at this stage determines the final yarn count – two threads produce a 2-ply yarn, three threads a 3-ply, and so on, each with different thickness and drape characteristics.
Stage 4: Twisting
This is the core mechanical step. The doubled bobbin is mounted on a twisting machine, which rotates the yarn as it is simultaneously wound onto a new bobbin. The twist is imparted because of the speed difference between the rotating spindle and the winding drum – the faster the relative rotation, the more twists per metre are inserted into the yarn.
The direction of twist matters as much as the quantity. There are four principal types of thrown silk yarn: organzine, tram, thrown singles, and crepe. Organzine – used for warp threads – is made by giving raw silk an initial twist in one direction, then plying two such threads together in the opposite direction. Tram, used for weft, involves twisting two or more threads in a single direction only. Crepe is produced by a high-twist process, while single thrown threads are used for sheer, lightweight fabrics. In Mysore silk production specifically, weft threads receive directional twists – S-twist (clockwise) for blue-tinted threads and Z-twist (anti-clockwise) for orange-tinted threads – in a two-stage process totalling 2,200 turns.
Stage 5: Heat setting (twist setting)
After twisting, the yarn has a strong internal tension locked into it – the twist is effectively under stress and wants to unwind. Heat setting stabilises it. Heat setting is required to set the twist on the thread so that distribution of twist along the yarn becomes uniform. The wound bobbins are loaded into a steam chamber (sometimes called a vacuum heat shelter), where controlled steam penetrates the yarn structure. The heat relaxes the internal stresses created during twisting, allowing the fibres to set in their new twisted configuration permanently.
In practice, silk threads wound on perforated hollow aluminium barrels are placed in a steam chamber for around 40 minutes. The perforations allow steam to reach the innermost layers of the bobbin evenly, ensuring no portion of the yarn remains undertreated. Without this step, the finished yarn would be unstable – it would kink, curl, or lose its twist during weaving, creating faults in the fabric.
Stage 6: Rewinding
The final stage prepares the set yarn for dispatch to the weaving or dyeing section. The rewinding machine functions similarly to the original winding machine, but since it handles doubled yarn, its production capacity is considerably higher. The yarn is transferred from the heat-set bobbins onto fresh bobbins, cones, or pirns suited to the next process. This step also serves as a final quality check – any residual defects in the yarn surface are detected and addressed before the yarn leaves the throwing section.
In operations producing yarn for traditional hank dyeing, the finished twisted yarn is wound back into hank form rather than onto bobbins, since hank dyeing requires loose, open packages through which dye can penetrate uniformly.
How twist level shapes the final fabric
The number of twists inserted per metre is not an arbitrary figure – it is a deliberate design decision that determines the physical and visual properties of the finished cloth. A low-twist yarn retains more of silk’s natural lustre and softness, making it well suited to lightweight, flowing fabrics. A high-twist yarn, by contrast, is denser and more resilient; crepe de Chine, for example, derives its characteristic cobblestone-like texture directly from highly twisted fibres. Medium-twist yarns balance strength and softness for general-purpose suiting and dress fabrics.
Twisting increases the yarn’s strength considerably and creates the compression required for efficient packaging – an often overlooked practical benefit. Twisted yarn holds its shape on the bobbin without matting or tangling, which reduces waste during transportation and storage. From the perspective of a weaver, receiving well-twisted yarn means fewer thread breaks at the loom, lower wastage, and a more consistent fabric output.
Twisting in the broader context of silk processing
Historically, silk throwing was originally a hand process – a worker would turn a large wheel called the gate, which twisted four threads, while a child assistant ran the length of a purpose-built shed of 23 to 32 metres to hook threads on stationary pins. The industrial revolution mechanised this process, and by 1700, Italian throwsters had developed two distinct machines – the filatoio for throwing and the torcitoio for doubling – that were far ahead of anything else in Europe at the time.
Today, modern Two-for-One (TFO) twisting machines insert two twists per revolution of the spindle, effectively doubling output compared to conventional machines while also improving yarn uniformity by reducing hairiness and dimensional variation. Automation has made it possible to control twist level, yarn tension, and feed speed precisely, allowing manufacturers to reproduce the same yarn specification consistently across large production batches – something that was impossible in the hand-throwing era.
What has not changed is the fundamental logic of the process. Whether the machine is an eighteenth-century Italian torcitoio or a contemporary TFO unit, the goal remains the same: transform a collection of fragile individual filaments into a coherent, strong, and workable yarn that can travel from the bobbin to the loom without breaking, and from the loom to the finished textile without losing its structure or beauty.
What do you think? Given that the direction and degree of twist determine whether a silk fabric turns out soft and lustrous or crisp and textured, how much creative control do you think the throwster (the person or facility doing the twisting) actually holds over the character of the final fabric? And as automation continues to advance in textile manufacturing, do you think the precision of machine-controlled twist settings will ever fully replace the nuanced judgement developed by experienced silk throwsters over decades of practice?
References
- https://www.britannica.com/topic/sericulture
- https://silkbynature.com/en/what-is-silk/from-the-cocoon-to-the-yarn-how-silk-is-born/
- https://www.torcituradidolzago.it/en/silk-twisting
- https://hbmahesh.weebly.com/uploads/3/4/2/2/3422804/silk_throwing_ppt.pdf
- https://arunyarns.com/the-process-of-making-silk/
- https://slidetodoc.com/silk-throwing-dr-mahesha-h-b-associate-professor/
- https://www.textilesphere.com/2021/10/yarn-doubling-and-twisting.html
- https://braveera.com/blogs/news/silk-production
- https://www.dsource.in/resource/mysore-silk/soaking-twisting-wefting
- https://silkyue.com/silk-production-process-steps-history-guide/
- https://www.dsource.in/resource/twisting-process/making-process
- https://en.wikipedia.org/wiki/Silk_throwing
- http://www.jxtwisting.com/?list_4%2F164.html=
Leave a Reply