Fibre swelling and shrinkage
Washing swells the fibre and drying deswells it. Shrinkage is a fabric travelling toward a fixed relaxed state — not a process that continues forever.
In detail
Consumer laundry advice asserts that hot washes shrink cotton and stops there. The cotton trade body's technical bulletin gives the mechanism, and it changes what the advice means. Washing wets out and SWELLS the fibre and yarn assembly under tensionless conditions; drying deswells it. Tumble drying adds mechanical tumbling with heat, and the bulletin states directly that tumble drying WITHOUT TENSION is a form of mechanical compression that allows maximum drying shrinkage to take place — which is why the dryer, not the wash, does most of the shrinking. The reassuring half is the concept of RELAXED DIMENSIONS: the state at which a fabric is fully relaxed and will not shrink further as a result of washing and tumble drying. A garment is travelling toward a fixed end point rather than shrinking indefinitely, which is why a much-washed shirt stops changing. So the variable to control is tension and agitation during drying rather than water temperature alone — line drying applies neither, which is why it is the conservative option.
Why
- Cotton is explained by Fibre swelling and shrinkage
- Wool is explained by Fibre swelling and shrinkage
Partial. The swelling account applies; wool felting is a separate mechanism no source held explains.
- Silk is explained by Fibre swelling and shrinkage
- Laminate flooring is explained by Fibre swelling and shrinkage
The reason a floor that looks like plastic behaves like wood.
- Finished wood flooring is explained by Fibre swelling and shrinkage
The route in is the SEAMS. Excess water does not sit on a wood floor, it travels down the joints into layers no cloth reaches.
Sources for this page
Sources
Technical Bulletin ISP-1009: Guide to Improved Shrinkage Performance of Cotton Fabrics
Cotton Incorporated · Trade or professional body
Relied on for: That washing swells the fibre assembly under tensionless conditions and tumble drying deswells it with mechanical tumbling and heat, that unrestrained tumble drying is a form of mechanical compression allowing maximum drying shrinkage, and that relaxed dimensions are the state beyond which a fabric will not shrink further. (states this directly)
Verification: a person has read the passage relied on.
Read on — The sections on relaxed dimensions and on swelling and deswelling. Supports the claim as stated.
Wool care: how to wash wool, and caring for wool
The Woolmark Company · Trade or professional body
Relied on for: That flat drying is recommended after washing, and that a Woolmark-approved machine-washable garment withstands repeated machine washing without shrinkage. (states this directly)
Verification: a person has read the passage relied on.
Read on — The "How to wash wool" page (machine and hand washing, drying) and the "Caring for wool" page (tumble drying, flat drying, detergent). Supports a narrower statement — our claim was reduced. These pages support the temperature, agitation and drying guidance but NOT the bleach position, which CleaningHQ had attributed here in Sprint 1. That claim was moved to woolmark-detergent-guidance, where the statement actually appears. CleaningHQ's felting explanation is not supported by Woolmark at all and is now carried by the fibre-science record as an interpretation rather than cited here.
Last reviewed by a person on .