Colourfastness on printed polyester is checked by testing a sealed sample for washing, rubbing, sublimation and light according to recognised methods, most commonly the ISO 105 series or the AATCC equivalents, and comparing the results against the grades your market expects. Disperse-printed polyester is generally robust, but a print that has not been properly fixed or washed off can bleed, mark other garments or migrate during storage. The test is cheap compared with a rejected shipment, so it should be a standard step between strike-off and bulk approval.
Polyester is printed with disperse dyes, which are fixed into the fibre by heat. If the fixation temperature or time is short, or if the loose dye on the surface is not washed off properly, the fabric can look fine on the roll and still fail in use. That is why a visual check is never enough.
The tests that matter for printed polyester
- Colourfastness to washing (ISO 105-C06 or AATCC 61): the sample is washed with a multifibre strip and graded for colour change and for staining of the adjacent fibres.
- Colourfastness to rubbing (ISO 105-X12 or AATCC 8): a dry and a wet white cloth are rubbed across the print and graded for colour transfer. Dark and heavily printed areas are the usual failures.
- Colourfastness to sublimation and dry heat (ISO 105-P01): the sample is pressed hot against undyed fabric to see whether dye migrates. This matters for anything that will be ironed, heat-transferred or stored in warm containers.
- Colourfastness to light (ISO 105-B02 or AATCC 16): the sample is exposed under a controlled lamp and graded against the blue wool scale. Important for curtains, sportswear and anything sold in sunny markets.
- Colourfastness to water and perspiration (ISO 105-E01 and E04): relevant for garments worn next to the skin.
How to sample properly
Take the sample from the bulk roll, not from the strike-off, and take it from the full width because fixation can vary from centre to selvedge. Seal it in a labelled bag with the roll number and sign across the seal so the result cannot be disputed. Send it to a lab accredited by the National Accreditation Board for Testing and Calibration Laboratories (NABL) or an equivalent body in your own market, and ask for the report to name the method and the grade for each test.
Reading the results
Grades run from 1 to 5, with 5 meaning no change. Many apparel buyers typically ask for grade 4 or better for washing and dry rubbing and accept slightly lower for wet rubbing, but the right level depends on the end use and your own standard. If a sample fails, the cure is usually a repeat wash-off and reduction clear at the process house, which is quick and cheap before the rolls leave the mill and expensive once they have shipped.
How Creston & Co helps
We take sealed samples from the bulk rolls during inspection, send them to an NABL-accredited lab and share the report with you before loading is approved. If a result is marginal we hold the rolls and work with the process house on a rewash before anything leaves the mill. A free 20-minute sourcing review is a good place to agree which tests and grades should go into your specification.