Why t-shirts twist after washing (spirality) and how to prevent it

Spirality, also called torque or garment twist, is a distortion of knitted fabric in which the wales, the columns of loops, no longer run at right angles to the courses, so the fabric leans. It is why a t-shirt twists after washing: when the first wash releases the stress in the yarn, the side seam swings towards the front or back. The main cause is twist left in the yarn, made worse by loose knitting and some fibres, especially viscose. It is prevented at the yarn and fabric stage, measured with ISO 16322 or AATCC TM179, and limited by an agreed percentage in the buyer’s specification.

What is spirality in knit fabric?

ISO 16322-3 defines spirality, or torque, in garments as a rotation, usually lateral, between different panels of a garment, caused by the release of latent stresses during laundering of the fabric. The same standard notes that fabrics from circular knitting machines can have inherent non-verticality of wale alignment, and that some constructions, such as denim, may have twist introduced on purpose.

In a flat piece of fabric, spirality looks like a rectangle leaning into a parallelogram. In a t-shirt it shows as:

• a side seam that runs diagonally across the front or back after washing;
• a hem that no longer sits level, with one corner dropped;
• stripes that no longer meet at the side seam;
• a placket or print that sits off centre after a few wears.

A 2019 study in Fibres & Textiles in Eastern Europe lists mismatched patterns, sewing difficulties, side-seam displacement and garment distortion as the typical quality problems spirality causes in t-shirt production.

Why does knitted fabric twist?

Spinning puts twist into yarn to hold its fibres together. That twist stores energy, which researchers call twist liveliness or residual torque. When the yarn is bent into loops on a circular knitting machine, the loops lean slightly in the direction the yarn wants to untwist. In single jersey every loop leans the same way, so the whole fabric leans.

Research published in the Indian Journal of Fibre & Textile Research found that relaxation through washing and tumble drying is what makes the spirality of the wales develop, and that its extent depends on how freely the unbalanced torque from yarn twist can relax. A tighter fabric, set by yarn count and stitch length, gives the yarn less room to rotate. An earlier study in the same journal concluded that any method of reducing spirality has to include a real reduction in the twist liveliness or torque in the yarn.

The knitting machine adds its own contribution. The 2019 study lists fabric density, tightness factor, loop length, machine gauge, number of feeders, yarn input tension and take-down tension among the knitting causes, and stentering, calendering, softeners, mercerising, resins and enzymes among the finishing causes.

Which fabrics and fibres twist most?

Single jersey is the classic case, and the 2019 study notes that spirality is especially frequent in single jersey made from regenerated cellulose fibres such as viscose and modal.

Fibre matters too. The 2019 study knitted 18 single jersey fabrics from nine fibres and blends on the same machine, all from 30/1 ring-spun yarn with the same twist multiplier. The highest spirality came from 100% viscose and 95% viscose / 5% polyester. In every fibre, the looser fabric twisted more than the tighter one.

Cotton Incorporated’s training slides on skewness put numbers on the yarn and knitting factors. All the fabrics are 100% cotton single jersey:

Source: Cotton Incorporated, skewness training slides. The twist rows are greige fabric measured after five home washes and tumble dries. The stitch-length row comes from a case study of a garment dyer whose t-shirts, knitted to a 0.139-inch specification, varied in skew from acceptable to more than 20%; it is total skew, the lean of the fully relaxed fabric.

Two lessons follow. Skew rose with every step up in twist multiple, and open-end yarn skewed far less than ring yarn at the same twist. And in the case study, shirts with a stitch 0.007 inches (about 0.18 mm) longer had 22.9% skew instead of 9.3%, more than double (our arithmetic), which is why a specification should fix stitch length, not only GSM. Twist direction decides which way the fabric leans: Z-twist yarns give a right-hand skew, with the wales leaning to the right, and S-twist yarns a left-hand skew.

How is spirality measured?

Two families of methods are used. ISO 16322-3 measures spirality or torque in woven and knitted garments after domestic laundering. Garments are conditioned, marked with reference lines, laundered to an ISO 6330 procedure agreed between the parties, and spirality is expressed as a percentage of a marked distance. The standard is explicit that it measures spirality after laundering, not as the garment was made. AATCC TM179 is the American method for skew change in fabrics and garment twist after home laundering.

A common garment calculation, used in the 2019 study, is:

Spirality % = 100 × B ÷ A, where B is how far the side seam has moved at the hem after washing and A is the side seam length.

As a worked illustration: a t-shirt with a 70 cm side seam whose seam has moved 3.5 cm at the hem after washing has 100 × 3.5 ÷ 70 = 5% spirality. Some labs report an angle in degrees instead, so check which unit your report uses before comparing it with a limit.

The AATCC TM179 formulas for fabric and garments

Cotton Incorporated’s training material on skewness sets out the two calculations in AATCC TM179, one for fabric and one for garments.

• Fabric (method 1, shear distortion). A 10-inch square ABCD is marked on the fabric before washing, and after laundering the two diagonals, AC and BD, are measured. Skew % = 2 × (AC − BD) × 100 ÷ (AC + BD). In Cotton Incorporated’s worked example, diagonals of 13.70 and 13.20 inches give 3.7%.
• Garments (method 2). A reference line AB is marked on the garment; after laundering, the distance AA′ that point A has moved sideways is measured. Skew % = AA′ × 100 ÷ AB. In the worked example, a 0.5-inch shift on a line of 18.75 inches gives 2.7%.

Two cautions. The test measures only the skew that occurs during the test, not the total skew a fabric is capable of, because earlier processing may already have released some of it, as the same Cotton Incorporated material points out. And the standard methods track each other closely: a 2008 study by researchers at Auburn University and Alexandria University, presented at the Beltwide Cotton Conferences, measured the same single jersey fabrics, knitted with elastane, by ASTM D3882, an ISO 6330 wash and AATCC 179, and found correlations of 0.88 to 0.99 between the results. Choose one method and keep it for every lot and reorder, and check the marking and calculation in the edition of TM179 your laboratory uses.

What spirality limit is acceptable?

No international standard sets a pass level. The limit is a line in the buyer’s specification, agreed with the method and the number of wash cycles. Published research gives useful context. The 2019 study cites earlier work treating a distortion above 5° as an important problem. It also chose spirality rates of 5%, 7% and 10% for its cutting trials because factories manage fabric below 5% with manual precautions on the spread, and rates above 10% were not common for the fabrics it studied.

Treat those as reference points, not targets. A plain white tee can hide a little twist that a striped rugby-style top or an engineered side-seam print cannot. Write the limit to suit the design, and use a tighter one where stripes or prints must line up.

Spirality, skew and shrinkage: how they differ

Three faults are often confused because they appear together on the same test report.

• Spirality or torque is the rotation of a knitted fabric or garment after laundering, from stress stored in the yarn. It shows as a twisting side seam or leg seam.
• Skew is a fabric in which the courses or weft threads are not at right angles to the wales or warp, so the fabric itself is distorted before it is ever washed. AATCC TM179 covers skew change in woven and knitted fabrics as well as twist in garments.
• Shrinkage is a change in length and width. Cotton Incorporated notes that in garment form shrinkage can come with seam puckering, torquing and changes to fit, which is why both are usually tested on the same washed garment.

The distinction matters when you reject a lot. A fabric can pass shrinkage and fail spirality, or the reverse, and each points the mill to a different part of its process: yarn and knitting for spirality, relaxation drying and compaction for shrinkage. ISO 16322-3 also notes that some fabrics, denim for example, have twist introduced on purpose, so a leg twist on jeans is judged differently from a twisting jersey tee.

What spirality costs before the garment is even washed

Twisted fabric wastes fabric in the cutting room. When the wales lean, the marker has to follow the wale line rather than the fabric edge, so pieces fit less tightly. In the 2019 study’s t-shirt markers, spirality of 5%, 7% and 10% cut the CAD fabric utilisation by 2.4%, 3.68% and 5.25% compared with fabric without spirality. On a large order, that is extra fabric paid for and thrown away, before any customer complaint.

The study also notes a practical trap: when wet fabric with high spirality is dried, the spirality can increase, and a fabric that still twists after dyeing and finishing may need to be re-processed, which costs time and money.

How to prevent t-shirt side seams twisting

Most of the fix happens before a garment factory sees the fabric.

• Specify the yarn. Ask for the yarn count, spinning system and twist level, not only “combed cotton”. Lower-torque yarns, open-end yarns and plied yarns all reduce twist, each with a different handle.
• Specify the knit. Fix the stitch length and machine gauge along with the GSM. Two fabrics of the same weight can twist very differently. The fabric and GSM guide explains why weight alone is not a full specification.
• Finish to relax. Relaxation drying and compaction, handled with low tension, remove stored stress before cutting.
• Balance the twist. Cotton Incorporated adds remedies at the yarn and machine: two-ply yarns of balanced twist, alternating feeds of S-twist and Z-twist yarns, S-twist yarns on clockwise-rotating machines and Z-twist on counter-clockwise ones, and, where feasible, a crosslinking resin finish, which relieves twist liveliness in most fabrics. For stripes, plaids and geometric prints it suggests considering resin or plied yarns.
• Test finished fabric per lot. Ask the mill for a spirality result on each lot, measured after washing, and reject lots above the limit before they reach the cutting table.
• Cut along the wale. The cutting room lays the marker to the wale line, not to the selvedge or fold, and checks the lean on the spread.
• Test the garment. Wash pre-production samples and bulk garments to the agreed method and measure the side seam.

Ask for the mill’s results on these tests when the jersey is booked through our fabric sourcing service, and for the wash test to be repeated on finished garments alongside our quality control checks.

Putting spirality into your tech pack

Add a testing line with four parts: the method (for example ISO 16322-3 or AATCC TM179), the wash procedure and number of cycles, the unit (percentage or degrees) and the maximum allowed. Put it next to the shrinkage limit, because the two are tested together and both come from the same yarn and finishing decisions. The tech pack guide shows where testing requirements sit.

If your design has horizontal stripes, side-seam prints or a boxy fit where any lean shows, say so on the front page of the tech pack so the mill knows the fabric needs extra care.

Next step

If you are developing jersey tees, the t-shirt manufacturing page covers fabrics, fits and the 500-piece minimum per style and colour. To agree a spirality and shrinkage specification before sampling, send us your tech pack, and we will reply within one working day.