Cotton
A cellulose fibre, tolerant of hot water and alkaline detergents — and measurably degraded by chlorine bleach, which cuts the cellulose chains themselves.
What not to do
Sodium hypochlorite (chlorine bleach) may damage Cotton
Best avoided
The available guidance advises against this.
Cumulative and invisible: the fabric looks fine and fails later, because the damage is to the cellulose chains rather than the appearance.
Precautions
- Limit the contact time
- Check the manufacturer's instructions
Evidence
Strongly supported
Sources
Scientific Reports (Nature Portfolio), 2023 · Scientific literature
Relied on for: That ten chlorine-based wash cycles reduced cotton cellulose limiting viscosity number by more than eighty per cent against about half after one hundred ordinary commercial cycles, with tensile strength falling correspondingly. (states this directly)
In detail
Cotton is almost pure cellulose, and cellulose tolerates conditions that destroy protein fibres: hot water, alkaline detergent, protease enzymes and mechanical agitation. That tolerance makes cotton the fibre most laundry advice is implicitly written for, and it is why advice that works perfectly on a cotton shirt can ruin a wool jumper. What cotton does not tolerate is chlorine, and the size of the difference is easy to underestimate because the damage is invisible until the garment fails. A peer-reviewed laundering study measured cellulose degradation directly and found that ten chlorine-based wash cycles reduced the cellulose limiting viscosity number by more than eighty per cent, against roughly half after one hundred ordinary commercial cycles — with tensile strength following. That study was of industrial laundering rather than a domestic wash, so the figures are not a household threshold; the direction and the scale of the effect are what carry across. Dyes, finishes and blends often impose tighter limits than the cotton itself does, which is why the care label rather than the fibre is the governing instruction on a made-up garment.
Properties
Sensitivity
- Alkalis
- Not known
- Chlorine bleach
- Sensitive
- Heat
- Not known
- Porous
- Sensitive
“Not known” means nobody has established this, not that the material is unaffected.
What works
Sodium percarbonate (oxygen bleach) requires the precaution Cotton
Safe only in specific conditions
This is only appropriate within specific limits. Outside those limits, no claim is made.
Coloured cotton is where the colour-change risk lies.
Only within these limits:
- Permitted only where the care label's bleaching triangle allows it — empty for any bleach, two oblique lines for oxygen only
- A crossed triangle excludes oxygen bleach too, and therefore excludes universal detergents containing it
- Stated consequence is colour change rather than fibre damage
The triangle is usually read as a question about bleach. The originating body applies it to detergent: 'do not use a universal detergent which contains oxygen for bleaching purposes, unless the bleaching symbol allows its use'.
Precautions
- Check the manufacturer's instructions
- Test on an inconspicuous area first
Evidence
Supported
Sources
GINETEX, The International Association for Textile Care Labelling · Standards body
Relied on for: That a universal detergent containing oxygen for bleaching purposes should not be used on coloured textiles unless the bleaching symbol allows it, with a stated risk of colour change, and that oxygen / non-chlorine bleach is contained in most universal detergents. (states this directly)
Why
- Cotton is explained by Adsorption of odour molecules
Why the fibre that holds odour is the one that smells less.
- Cotton is explained by Fibre swelling and shrinkage
- Cotton is explained by Oxidation and bleaching
Ten chlorine washes did more damage to the cellulose than one hundred ordinary ones.
- Cotton is explained by Penetration into fibres
- Cotton is explained by Why plant fibres turn brown when they dry slowly
Related
- Cotton is commonly affected by Perspiration
- Cotton is commonly affected by Sunscreen
- Cotton is commonly affected by Antiperspirant residue
- Cotton is commonly affected by Tomato stain
- Cotton is commonly affected by Mustard stain
- Cotton is commonly affected by Fruit juice
- Cotton is commonly affected by Hair dye
- Cotton is commonly affected by Makeup
- Cotton is commonly affected by Mildew
- Cotton is commonly affected by Cellulolytic microorganisms
- Cotton is commonly affected by Mould fungi
Hacks and claims involving this
- Hotter washes clean better Disputed
- Hot water for a blood stain Does not work
- A stronger solution cleans better Does not work
- Freezing chewing gum off with ice Unresolved
- Washing silk at home Disputed
- Lifting candle wax with a warm iron and paper Unresolved
- Drying wool flat rather than hanging it Supported
- The care label allows oxygen bleach even when it bans chlorine Does not work
- The dots on a care label are just a rough guide Does not work
- Fabric softener is fine on everything Does not work
- Washing cold prevents shrinking Disputed
- A stain method that works on cotton works on anything Does not work
- Orange sunscreen marks are rust Does not work
- Melting candle wax out with an iron and paper Unresolved
- Leaving a stain in the sun to fade it Plausible mechanism, untested in this application
Sources for this page
Sources
Scientific Reports (Nature Portfolio), 2023 · Scientific literature
Relied on for: That chlorine-based laundering degrades cotton cellulose far faster than ordinary washing, measured as limiting viscosity number and tensile strength loss, and that cotton-polyester blends retain strength better than pure cotton. (states this directly)