What is spirality (skew) and why does it appear in single jersey knits?
A knit fabric is made up of interlocked loops. Each loop carries a slight tendency to rotate, driven by the twist imparted to the yarn. In double-faced structures (interlock, rib) these tendencies largely cancel one another between the front and back needle beds. In single jersey structures such as single jersey, by contrast, there is no balancing reverse face; the accumulated torque of the yarn skews the loop courses and spirality becomes visible.
The direction and severity of skew depend on the interaction of three variables: the twist direction of the yarn (Z or S) and the amount of twist, the knitting density (tightness/loop length), and the permanent setting applied to the fabric during finishing. Spirality is therefore not merely a knitting fault but the outcome of a chain that runs from yarn to garment making-up, and its control is likewise exercised at several links of that same chain.
In practice, spirality is assessed as the displacement angle between two points marked across the fabric width, or as the deviation of the side seam from the horizontal axis. The fabric width and the tubular/open-width form also affect how skew shows up during measurement and cutting; in tubular knitting, skew can be perceived more clearly once the fabric is slit to open width.
How does yarn twist determine skew?
A spun yarn carries a certain amount of twist to hold the fibres together. While this twist gives the yarn tensile strength, it also creates a tendency to untwist when released (residual torque). When the yarn enters the knitted structure this torque cannot be fully released; it accumulates within the loop geometry and is discharged as the courses skew. With the same knitting setting, therefore, a high-twist ring yarn and a low-twist yarn give markedly different skew.
The yarn production method is also decisive. Open-end yarns generally carry a different twist character from ring yarns; compact yarn, meanwhile, offers a smoother structure with less hairiness. In addition, plied yarns, obtained by twisting two yarns together in the opposite direction, balance torque to a large degree compared with a single-ply yarn; this is why, in some single jersey fabrics, the skew problem is reduced from the outset by choosing a plied or specially balanced yarn.
The fibre type also alters the effect. While cleaned and smoothed yarns such as combed cotton behave more predictably, the moisture uptake and swelling behaviour of regenerated cellulosic fibres such as viscose or modal brings post-wash dimensional change onto the agenda as a separate parameter.
| Yarn parameter | Effect on skew/shrinkage | Control approach |
|---|---|---|
| Amount of twist (high) | Residual torque increases, spirality severity rises | Choosing a balanced/low residual-torque yarn; verification on a sample |
| Twist direction (Z / S) | Determines the direction of skew (right/left) | Matching knitting direction to twist direction; feed balance across multiple feeders where needed |
| Single-ply vs. plied | Plied yarn balances torque to a large degree | Plied or specially balanced yarn for critical products |
| Yarn type (ring/open-end/compact) | Twist character and evenness differ | Selecting yarn type by end use and securing consistent supply |
| Fibre type (cotton/viscose/modal) | Moisture uptake and swelling affect wash shrinkage | Additional dimensional testing and finishing adjustment for cellulosic blends |
What is the difference between dimensional stability and spirality?
Dimensional stability measures dimensional change: a sample is marked, washed and dried under a defined programme, and the dimensions are compared. A negative value indicates shrinkage, a positive value extension. Spirality is assessed on the same sample by the distortion of the angle between vertical and horizontal reference lines. A fabric can be very stable dimensionally and yet still skew visibly; the two properties are therefore reported separately.
The common root is this: knit fabric is held under tension in the machine direction throughout production and finishing. The loops elongate under this tension; when the tension is removed and the fabric is washed, the loops seek to return to their natural (relaxed) geometry. This recovery manifests both as lengthwise/widthwise shrinkage and, as the torque is discharged, as skew. The essence of control, therefore, is to bring the fabric as close as possible to its relaxed state before consumer laundering.
Within this framework, weight and tightness also play a role: a very loosely knitted fabric carries more recovery-shrinkage potential, while excessively tight knitting can create different tension problems. Target weight, width and skew tolerances should be defined together from the outset; how these are measured and reported is covered holistically in our quality and testing guide.
How do sanforising and compacting control shrinkage and skew?
Most of the shrinkage in knit fabric is in the lengthwise direction, because the fabric is tensioned most in this direction along the production line. In the sanforising (compressive shrinkage) process the fabric is compressed lengthwise in a controlled manner on an elastic blanket; this pre-releases the tension that would emerge in laundering and reduces permanent shrinkage. Compacting works on a similar principle, increasing the loop density for single jersey knits and improving dimensional stability.
From the skew point of view, the critical point is that the fabric enters and is set in finishing straight (without axis migration). On the stenter line the width and weft straightness are adjusted; in structures containing synthetics or elastane the fabric is thermally set by heat-set. In knits containing spandex/elastane, heat setting is decisive for both dimensional stability and recovery; we cover this topic in detail in the spandex/elastane knitting guide.
The process sequence and tension management also change the outcome. If the fabric is repeatedly tensioned during the pre-treatment and finishing steps, the final mechanical setting may not fully compensate for this accumulation. Shrinkage and skew control therefore depend not on a single machine but on tension discipline from pre-treatment through to the final finish.
| Production/finishing parameter | Possible cause | Control point |
|---|---|---|
| Knitting tightness / loop length | Loose knitting gives excess recovery-shrinkage potential; torque build-up | Fixing target weight and loop length via a sample |
| Lengthwise tension (production line) | Loops elongate, lengthwise shrinkage emerges in laundering | Pre-shrinking by sanforising / compacting |
| Stenter width and weft straightness | Skewed laying-out increases spirality | Weft straightening and symmetrical laying-out on the stenter |
| Thermal setting (synthetic/elastane) | An unset structure deforms in laundering | Heat-set temperature/time control |
| Yarn torque (source) | Unbalanced torque gives permanent skew | Balanced/plied yarn + knitting-twist matching |
How is wash shrinkage measured and tied to tolerance?
For the measurement to be reliable the method must be standardised. Common references for dimensional change and skew are the ISO and AATCC families; sample marking, the wash programme, the drying method and the conditioning steps directly affect the result. The laboratory and the customer care instructions (wash temperature, drying method) must therefore be consistent; otherwise the laboratory result and the consumer experience diverge.
Shrinkage and skew are usually tracked not once but over several wash cycles, because residual tension tends to emerge in the first few washes. When reporting is done as a percentage change and skew angle rather than an absolute dimensional difference, comparison across different widths/lengths becomes possible. How these measurements sit within a test package alongside other quality criteria such as pilling and fastness is covered on the shrinkage testing and dimensional stability page.
An important point: GSM tolerance, width tolerance and skew tolerance are interdependent. A tighter shrinkage target usually means more intensive mechanical setting and therefore an effect on weight/width. Targets should therefore not be defined in isolation but together, and verified together at sample approval. As specific tolerance figures vary by product and end use, let us clarify these together on a project basis.
How can I reduce skew and shrinkage risk in the design from the outset?
The first decision is at fibre and yarn level. In products where side-seam migration is unacceptable, choosing a balanced or plied yarn reduces skew at source. The second decision is the choice of structure: double-faced structures such as interlock or rib naturally skew less; when single jersey single jersey is chosen, the skew risk must be accepted from the outset and managed through finishing. For structure selection and the differences, see the single jersey versus interlock comparison.
The third decision is the tightness and weight target. Very loose knitting carries more recovery-shrinkage and skew potential; setting the target weight by the product's use also defines what the finishing must compensate for. In products where recovery is critical, such as activewear, the elastane and thermal-setting strategy comes to the fore; in this area we recommend the activewear and legging fabric guide.
Finally, the control is verified with a sample. Lab-dip and physical sample approval are a reference not only for colour, but also for dimensional stability and skew. When the pre-production sample is approved together with the target tolerances, surprises in bulk production are largely prevented. This discipline makes shrinkage and skew predictable and ensures consistency in the B2B supply chain.
Frequently asked questions
Why does spirality (torque skew) appear especially in single jersey fabrics?
Because a single jersey structure has no opposing face to balance the torque generated by the yarn twist. In double-faced structures such as interlock and rib, the spirality tendencies of the front and back needle beds largely cancel each other out. Without this balancing in single jersey, the yarn's accumulated torque skews the loop courses and the spirality becomes visible; its most noticeable result is the side seam migrating around the body toward the front.
How does yarn twist affect spirality, and which yarn choice reduces the problem?
The twist direction (Z or S) determines the direction of the skew, while the twist level determines its severity. Higher twist means more residual torque, and that torque rotates the loops in single jersey knitting. The most effective decision is to select a balanced yarn, meaning one with low residual torque. Because a plied yarn made by twisting two yarns in opposite directions largely cancels out the torque, plied or specially balanced yarn is preferred for critical products.
Are dimensional stability and spirality the same thing? What are the differences?
No, they are separate defects and are reported separately. Dimensional stability is the fabric's ability to retain its width and length measurements after washing and drying; the outcome appears as shrinkage or extension. Spirality, on the other hand, is the angular displacement of the loop courses. A fabric can be highly stable dimensionally and still skew visibly. They share common roots: tension not set during finishing and unbalanced yarn torque.
How do sanforizing and compacting control shrinkage and spirality?
These are mechanical finishing processes that compress the fabric lengthwise in a controlled manner, bringing the loops closer to their relaxed geometry, so that the shrinkage which would otherwise appear in consumer laundering is taken out in advance. In sanforizing, the fabric is compressed lengthwise on an elastic blanket and permanent shrinkage is reduced. Compacting increases the loop density for single jersey knits. For spirality, the critical point is that the fabric enters finishing without going off-axis and is set straight.
How is wash shrinkage measured and which standards is it based on?
A marked specimen is washed and dried under a standard program; its width and length measurements are compared and the result is reported as a percentage. The spirality angle is assessed on the same specimen. The common references are the ISO and AATCC families. Shrinkage and spirality are usually tracked over multiple wash cycles, because residual tension is released in the first few washes. The laboratory program must be consistent with the customer's care instructions.
How can I reduce the risk of spirality and shrinkage from the start at the design stage?
The most effective control is to reduce the problem in design rather than to correct it after production. Select a balanced or plied yarn, set a stitch density and weight appropriate to the structure, and where needed consider a double-faced structure such as interlock or rib instead of spirality-prone single jersey constructions. Define the target width, weight and spirality tolerances together and lock them in at pre-production sample approval; the lab dip and the physical sample are a reference not only for color but also for dimensions and spirality.