What should I check when a moisture-wicking undershirt does not wick?

Short answer: Start by separating the fabric from the care routine. Wicking performance comes from fibre, yarn and knit structure, and sometimes a hydrophilic finish. Fabric softener residue, a finish that washes out, or a fit that does not touch the skin can all make a correctly specified fabric feel like it is not wicking. Test before and after laundering to know which applies.

How wicking works

A wicking fabric moves liquid sweat away from the skin by capillary action through fibres and yarn channels, then spreads it so it can evaporate. Synthetic yarns with engineered cross-sections and certain knit structures do this mechanically; other fabrics rely partly on a chemical finish that makes fibres attract water. Finishes can lose effect as they wear out with laundering.

Common reasons it stops working

• Fabric softener: softeners coat fibres and can block moisture transport. Many performance care labels advise against them.
• Finish durability: a finish-dependent fabric may wick well when new and less after repeated washes.
• Fibre and blend: high cotton content absorbs and holds water rather than moving it.
• Fit: a loose undershirt does not touch the skin, so it cannot pull sweat away.
• Expectation: wicking helps comfort but does not stop sweating; in heavy sweating any fabric becomes wet.

How to test and specify

• Use a recognised method such as AATCC TM195, which measures and classifies liquid moisture management of fabrics. Agree the classification you require.
• Test after an agreed number of washes using a defined procedure such as ISO 6330, not only on new fabric.
• Write care instructions that match the tested conditions, including softener guidance.

Limits

Do not publish performance claims such as "dries X times faster" without test data that supports the exact wording. If the fabric is finish-dependent, describe it honestly and avoid durability promises you have not tested.

Facts, recommendations and uncertainty

Established: softener residue and finish wear can reduce moisture transport. Recommendation: test before and after washing with a named method. Uncertain: performance in heavy sweating, where every fabric eventually becomes wet.

Sources and further reading

• AATCC TM195 — Liquid moisture management properties of textile fabrics
• ISO 6330:2021 — Domestic washing and drying procedures for textile testing
• U.S. FTC — Care Labeling Rule (16 CFR Part 423)

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.