Why did new underwear bleed colour in the first wash?

Short answer: Some loose dye in the first wash can happen with deep shades, but visible staining of other garments usually means the fabric still carried unfixed or poorly washed-off dye. It is largely controllable through dye selection, fixation and thorough washing-off at the dyehouse, and it can be measured with a colourfastness-to-washing test that rates staining on adjacent fabrics. Clear care instructions help, but they should not be the only safeguard.

Why bleeding happens

In reactive dyeing of cotton and other cellulose fibres, part of the dye reacts with the fibre and part remains unfixed or is hydrolysed. The unfixed dye must be removed by soaping and rinsing after dyeing; if this washing-off is shortened, residual dye comes out in the customer's machine. Deep shades such as red, navy and black carry more dye and so more potential residue. On synthetic fibres, dye migration and surface dye can cause similar staining, especially after heat.

How to test it

ISO 105-C06 assesses colourfastness to domestic and commercial laundering: a specimen is washed together with a multifibre adjacent fabric, and both colour change of the specimen and staining of the adjacent fibres are rated with grey scales. Staining is the result that predicts the "pink T-shirt" complaint. Agree the test conditions and minimum grades with your laboratory and mill for each colour group, and test dark and bright shades from production, not only lab dips.

What to specify

• Minimum staining and colour-change grades after washing for each colour group.
• Rubbing fastness for deep shades.
• That washing-off and fixation follow the dye supplier's recommendations for the shade.
• A pre-shipment test for deep shades on each new dye lot.

Care instructions

Advise washing dark and bright colours separately for the first washes and turning garments inside out. Keep the advice consistent with your wash tests and the care label.

Diagnosing a complaint

Wash a retained garment from the same lot with a white fabric under the label's conditions. If it stains, the dyeing or washing-off needs review. If it does not, check whether the customer washed at a much higher temperature than recommended.

Limits

A grade that passes in the laboratory reduces risk but cannot guarantee zero dye release in every machine, especially at high temperatures or with long soaking.

Facts, recommendations and uncertainty

Established: staining comes from unfixed or poorly removed dye and is measured by ISO 105-C06 with grey scales. Recommendation: set staining grades for deep shades and test production lots. Uncertain: behaviour in very hot or long washes outside the label's instructions.

Sources and further reading

• ISO 105-C06:2010 — Colour fastness to domestic and commercial laundering
• ISO 105-A02:1993 — Grey scale for assessing change in colour
• ISO 6330:2021 — Domestic washing and drying procedures for textile testing

Standards and regulations are referenced by their published scope. Test parameters, cycles and pass levels should be agreed with your laboratory for the specific product; legal requirements should be confirmed for each destination market.