Shrinkage, spirality and pilling: the wash tests and the tolerances to set

Three faults appear only after a garment has been washed or worn: it shrinks, its side seams twist, or its surface balls into small pills. All three can be measured before bulk is cut, and each has a standard test. A buyer who writes the limits into the tech pack and approves a washed sample turns a likely customer complaint into a pass or fail result from the laboratory. This guide explains the cause of each fault, the tolerance usually set by fabric, and the method that measures it.

Garments Hub BD is a sourcing desk; factories on its bench make the goods. Inline inspection runs during sewing, and a final random inspection is held at 80 percent packed, to AQL 2.5 unless you set another level, with every stage photographed. Limits written into the tech pack give the inspections and the laboratory a figure to work to.

Shrinkage: why it happens and how it is measured

Fabric is stretched as it is knitted or woven, dyed and dried. In the first washes the fibres swell and the yarns relax back towards their natural length, so the cloth shrinks. Cotton and viscose move the most; polyester and nylon move little. The test is simple in principle: mark a sample, wash and dry it by a set procedure, and measure again. ISO 5077 with ISO 6330 procedures is the international method; AATCC 135 covers fabrics and AATCC 150 covers garments.

A worked example. Two marks 50 cm apart along the length of a jersey sample measure 48.0 cm after washing. The change is 48.0 minus 50.0, divided by 50.0: minus 4 percent, so the fabric shrank 4 percent in length. Width is measured the same way, and a fabric that grows shows a plus figure.

The wash procedure must be stated, because the result depends on it. Name the temperature, the number of cycles (three is common) and the drying method. Tumble drying usually shows more shrinkage on cotton than line drying, so the test should follow the care label you intend to sew in.

Shrinkage tolerances buyers usually set by fabric

These are common starting points for length and width after the stated home wash. Tighter limits are possible, but they usually need an extra finishing step at the mill, and that step costs time and money. Where a garment combines fabrics, such as a jersey body with a woven trim, set a limit for each.

• Cotton single jersey and rib: usually 3 to 5 percent.
• Fleece and French terry: usually up to about 5 percent, with heavy loopback terry relaxing most in length.
• Linen: usually 3 to 5 percent on cloth washed at the mill; unwashed linen can move considerably more.
• Viscose: usually 3 to 5 percent; viscose is weak when wet and shrinks more if washed hot.
• Denim: untreated rigid denim can shrink 10 percent or more; mechanically pre-shrunk denim is usually held to about 3 percent.
• Wool knitwear: usually 3 to 5 percent under the gentle wash on the care label, since heat and agitation felt wool.

Why single jersey twists, and what controls it

Spirality shows after washing: the side seams of a jersey tee swing towards the front and the hem twists. Single jersey is an unbalanced fabric. The twist in a single ply yarn wants to unwind, and circular machines with many feeders lay the courses at a slight angle, so the loops lean. Interlock and rib are balanced constructions and twist far less.

The controls sit in the yarn and the finishing, not in the sewing. Lower twist or plied yarns reduce the torque. Relaxing the fabric before cutting and compacting it at finishing hold both twist and shrinkage. Open width finishing lets the wales be set straight, which tubular fabric does not allow, and cutting along the wale line keeps the twist out of the panels. Buyers usually set a limit of 5 percent or less after washing, tested to ISO 16322. A worked example: a side seam that has moved 3 cm at the hem over a 70 cm body length shows about 4.3 percent twist.

Pilling on polyester and brushed cloth

Pills form when loose fibre ends work out of the surface during wear and tangle into small balls. On cotton, weak pills tend to break off. Polyester and nylon fibres are strong, so their pills stay anchored and the garment looks worn early. Brushed fleece, spun polyester blends, soft low twist yarns and fine wool or cashmere knitwear pill the most.

Pilling is tested with ISO 12945-1 (the pilling box) or ISO 12945-2 (the modified Martindale), and graded 1 to 5 against reference photographs, where 5 means no pilling. Buyers commonly ask for grade 3-4 on knitwear and fleece. The controls are tighter yarn twist, longer fibres or filament yarn, and a finish that removes surface fibre, such as shearing or an enzyme wash on cotton.

The pre-shrink allowance cut into the pattern

Some garments are meant to shrink: garment dyed styles and washed denim go through a wash after sewing. For these, the pattern is cut larger by the measured shrinkage so that the washed garment lands on the size chart. A worked example: if a twill shrinks 6 percent in length through garment dyeing, a finished inseam of 81 cm is cut at about 86 cm. The allowance must come from the bulk fabric through the real wash, measured by size. For fabric that will not be washed after sewing, stabilise it at the mill instead, since an allowance cannot correct cloth that shrinks unevenly.

Approving a washed sample before bulk

Wash the PP sample, or a set of sizes, to the care label for the agreed number of cycles before you approve it. Measure every point against the size chart, check side seam twist, and look at the surface, the seams, any print and the labels. Ask for the fabric test reports on the bulk lots before cutting, so a lot that fails goes back for refinishing instead of into garments. A laboratory test adds days to the timeline, which is easier to plan at the quote than to find later.

What to put in your specification for washing

• Shrinkage limitA maximum for length and width, for example 5 percent on cotton jersey, by fabric if the garment has several.
• Wash procedureThe ISO 6330 or AATCC procedure, temperature, number of cycles and drying method, matching the care label.
• Spirality limitUsually 5 percent or less on single jersey after washing, measured to ISO 16322.
• Pilling gradeISO 12945-1 or ISO 12945-2, with the minimum grade, commonly 3-4 on knitwear and fleece.
• What is testedBulk fabric by lot before cutting, and finished garments as well, since sewing and pressing add change.
• Washed sampleThe PP sample washed, measured and approved in writing before bulk cutting starts.
• Pattern allowanceFor garment dyed and washed styles, the shrinkage measured on bulk fabric and added to the pattern by size.

Questions buyers ask