Wash testing is a laboratory check of how a garment or fabric behaves after it has been washed, usually a set number of times under a defined method. It measures shrinkage in length and width, change in colour, staining of adjacent fabrics, and the appearance of seams, prints and trims after washing. The tests follow published methods, most often from AATCC or ISO, so that a result from one laboratory can be compared with a result from another.
The purpose is simple. A garment that fits in the store and shrinks a size in the first wash is a return, and a dark garment that stains a white load is a complaint. Wash testing before bulk production tells you what will happen before your customer finds out.
What a standard wash test covers
- Dimensional stability, meaning the percentage shrinkage or growth in length and width after washing and drying.
- Colour fastness to washing, graded for colour change and for staining of white and multifibre test strips.
- Appearance after washing, including seam puckering, twisting or torque of the garment, and pilling.
- Durability of prints, embroidery, labels and trims through the wash cycle.
- Fastness to other actions where relevant, such as rubbing, perspiration and light.
How the methods work
The AATCC methods are widely used by buyers in the US, while the ISO 6330 wash procedure and the ISO 105 colour fastness series are the usual reference in Europe and much of the rest of the world. Both define the machine type, water temperature, detergent, load and drying method, so that the test reproduces a defined home laundering condition rather than whatever the laboratory happens to do.
Colour fastness results are graded on a scale of one to five using grey scales, where five means no change and one means severe change. Buyers typically ask for grade four or better for colour change and grade three to four or better for staining on cotton garments, with stricter requirements for white or pastel goods.
Shrinkage limits are set by the buyer. A common requirement for woven cotton garments is within a few percent in each direction after a set number of washes, and knits are usually allowed a little more. The spec sheet should state the limit and the number of washes it applies to.
When to test and what to send
Test at two points. Test the bulk fabric before cutting, so that a shrinkage or fastness problem is caught while the fabric can still be rejected or treated, and test finished garments from the first production output, because seams, prints and trims can behave differently from the plain fabric.
Send sealed samples to an accredited laboratory rather than relying on the factory's own results. A factory in-house test can be a useful early warning, but it is not independent and will not be accepted in a dispute. Ask for the test report to name the method, the number of cycles and the temperature used.
How Creston & Co helps
We draw and seal samples from bulk fabric and from first production, send them to an NABL-accredited laboratory for wash testing to the AATCC or ISO method you specify, and share the report with you before cutting or shipment goes ahead. We also check during inline inspection that the fabric on the line matches the tested lot. A free 20-minute sourcing review is a good place to set your wash requirements for a new range.