How to Remove Mould from Clothes
Never brush mould off indoors. Spores become airborne and can colonise other surfaces. Take the garment outside, wear a face mask.
If the fabric feels weak or tears easily, mould enzymes have already degraded the fibres. The weakening is permanent — treatment stops further damage but does not restore strength.
Fungal Biology — How Mould Damages Fabric Fibres
Mould is a multicellular fungus that reproduces through microscopic spores. When mould spores land on a damp fabric in a warm environment (above 15°C with relative humidity above 60–65%), they germinate and grow thread-like structures called hyphae into and across the fabric surface. The visible mould growth you see — the white fuzzy layer, black spots, or green patches — is a combination of the hyphal mat and the pigmented spores the mould is producing. The critical distinction for fabric damage is between surface mould and embedded mould. Surface mould (hyphae growing on top of the fabric without penetrating the fibre structure) can be treated and removed without permanent fibre damage. Embedded mould (hyphae that have grown into the fibre structure) causes physical degradation that cannot be reversed. Mould damages natural fibres through enzyme secretion. On cotton and linen (cellulose fibres), mould secretes cellulase enzymes — enzymes that break the β-1,4-glycosidic bonds in the cellulose polymer chain. Over time, this progressively shortens the cellulose chains, weakening the fibre. On wool and silk (protein fibres), mould secretes protease enzymes that break peptide bonds in the fibre protein structure. The same enzymatic damage that makes biological laundry detergent effective on stains is, when applied continuously by mould, the mechanism of fibre destruction. The staining from mould comes from the pigments in the fungal spores and hyphae — typically melanin-based pigments (black/brown stains from Aspergillus niger and similar species) or carotenoid pigments (green from Penicillium or Aspergillus fumigatus, pink from Fusarium, etc.). These pigments are embedded within or below the fibre surface and require oxidative treatment to break down. Sodium hypochlorite (chlorine bleach) is highly effective at killing mould and oxidising the pigments, but it damages cellulose and protein fibres over time. Sodium percarbonate (oxygen bleach — releasing H₂O₂) is gentler and effective for both killing mould and breaking the pigment chromophores. The heat of a 60°C wash is sufficient to kill most mould spores and hyphae on cotton. The key practical risk of treating mould is spreading live spores — if you handle mouldy fabric indoors without precautions, spores become airborne and can colonise other surfaces. Always brush off loose mould outdoors, wearing a face mask, before bringing the garment back inside for treatment.
Treatment Steps
Assess the damage — test fibre strength before treating
Before treating, assess whether the fabric fibres have already been degraded. Take a section of the heavily moulded area and gently tug the fabric between two hands. If the fabric tears with minimal force, or if you can see the weave structure has been weakened or pitted, the mould enzymes have already degraded the fibre and the weakening is permanent. Treating and removing the mould will stop further damage but will not restore tensile strength. For lightly moulded fabric where the structure feels intact, full recovery is possible.
Brush off loose mould outdoors — never inside
Take the garment outside and use a stiff brush to remove as much surface mould growth as possible. Do this outdoors, ideally wearing a face mask (N95 or FFP2), as brushing disturbs spores and makes them airborne. Spores inhaled in quantity can cause respiratory irritation. Do not shake the garment indoors. After brushing, place the garment directly into a sealed plastic bag until you are ready to wash it — this prevents spores from dispersing around your home.
Pre-soak in sodium percarbonate solution
Dissolve 2–3 tablespoons of sodium percarbonate (Vanish Gold, OxiClean, or pure powder) in a bucket of warm water (40–50°C). Submerge the garment fully and soak for 1–2 hours. Sodium percarbonate releases hydrogen peroxide in warm water, which both kills mould spores and hyphae and begins breaking down the melanin and carotenoid pigments causing the staining. For heavily stained areas (black spots), rub a paste of sodium percarbonate mixed with a small amount of water directly into the stain before soaking.
Machine wash at the highest safe temperature
For cotton and linen: wash at 60°C — hot water kills any remaining spores and hyphae. Add extra sodium percarbonate to the drum. For wool and silk: do not exceed 30°C — these fibres felt or degrade at higher temperatures. Use a wool-specific detergent with no bleach. For cotton-polyester blends: check the care label, but 40–60°C is typically safe. Add white vinegar (200ml) to the fabric softener drawer in the final rinse — the mild acid helps remove mineral residue from the mould treatment.
Dry thoroughly in direct sunlight if possible
UV radiation from sunlight kills residual mould spores and has a bleaching effect on residual staining. Air dry in direct sunlight if available. If air drying indoors, ensure full airflow — do not dry in a damp room or cupboard as any residual moisture and spores will allow regrowth. Tumble drying at high heat achieves the same kill effect as sunlight.
Inspect and repeat if staining remains
Check the treated area once dry. If grey-black shadow staining remains after treatment, the mould pigment is deeply embedded. Repeat the sodium percarbonate soak for 2–4 hours, or for cotton only, apply diluted chlorine bleach (1 tablespoon per litre of water) for 15–20 minutes — do not exceed this time and rinse thoroughly. On wool and silk, do not use any bleach — residual staining on delicate moulded fabric may be irreversible.
Risk and Treatment by Fabric
| Fabric | Treatment | Recovery |
|---|---|---|
| Cotton (clothing) | 60°C wash + sodium percarbonate | Good if caught early Cellulase enzymes weaken cotton with prolonged mould growth. |
| Linen | 60°C wash + sodium percarbonate | Good if caught early Same cellulose structure as cotton — same degradation risk. |
| Wool / cashmere | 30°C wash, wool detergent, no bleach | Partial — pigment may persist Protease enzymes degrade wool protein. No hot water or bleach. |
| Silk | Cool hand wash, no bleach | Often limited Protein fibre. Very sensitive to bleach and high temperatures. |
| Polyester / nylon | 40°C wash + sodium percarbonate | Excellent Synthetics do not provide nutrients for mould enzyme digestion — surface growth only, no fibre degradation. |
| Down-filled items | 60°C wash (if care label allows), tumble dry thoroughly | Variable Down is a protein fill material. Mould inside baffles is very hard to remove without professional treatment. |
FAQ
Can mould permanently damage clothes?
Yes. Mould secretes enzymes that break down fibre polymer chains — cellulase for cellulose fibres (cotton, linen) and protease for protein fibres (wool, silk). This physical degradation of the fibre structure is irreversible: you can kill the mould and remove the surface staining, but weakened fibres will not regain their original tensile strength. The earlier mould is treated, the less fibre damage occurs. Surface mould of a few days or a couple of weeks typically causes limited or no permanent damage. Mould left for months in damp storage conditions can make cotton or wool garments structurally unsound.
Can you use bleach on mouldy clothes?
Chlorine bleach (sodium hypochlorite) is effective at killing mould and oxidising the pigments but should be used with caution. It damages cotton fibres with repeated use (oxidises cellulose), and it must not be used on wool, silk, or any coloured fabric (it will strip the dye). For cotton, a diluted chlorine bleach soak (1 tablespoon per litre) for 15–20 minutes followed by thorough rinsing is safe for occasional heavy-mould treatment. Sodium percarbonate (oxygen bleach) is gentler and effective for both cotton and, at lower concentrations, colour-safe versions can be used on most fabrics except wool and silk.
Why does mould keep coming back on clothes in storage?
Mould regrows if either of two conditions is met: residual live spores remain in the fabric (treatment was incomplete), or the storage conditions provide the necessary humidity (above 60–65% relative humidity) and temperature (above 15°C) for germination of new spores from the environment. Treating the garment removes the current mould, but does not prevent spores from the storage environment from colonising again. The permanent solution is to reduce humidity in the storage area — a dehumidifier, cedar blocks (which inhibit mould growth), or moisture-absorbing packets. Never store clothes that are even slightly damp.
Is it safe to wash mouldy clothes in your washing machine?
Yes, if you take precautions. First, brush off loose mould outdoors to reduce the spore load. Then wash the mouldy item, ideally alone or with other badly affected items, at the highest safe temperature with sodium percarbonate. After the wash, run the empty machine on a hot cycle (60°C) with a cup of white vinegar or a washing machine cleaner to kill any spores that may have been deposited in the drum, seal, or detergent drawer.
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