Killing mould and removing the stain are two different jobs. What you see is not the mould but the dye it left behind, and that stays put long after the organism itself is dead.
Short answer
Brush it out outdoors once it is dry, then soak in cold water with oxygen bleach, then wash.
On white cotton the stain usually comes out. On coloured or delicate fabrics a shadow often stays behind, and that, frankly, is where the limit lies.
What those stains actually are
Two names for the same thing, and one misunderstanding that decides the approach.
If textiles lie damp for too long, mould spores start to grow. That happens in a full laundry basket, in a bag with wet sports kit, in a tent that was packed away damp, or in a wardrobe against a cold outside wall.
What you see afterwards are small grey, black or brown spots. In the Netherlands one person calls that mould and the next calls it "het weer" in the clothing. It is the same thing.
And here is the misunderstanding. Those spots are not the mould itself but the dye it has deposited in the fibre. A product that kills mould therefore does nothing about what you can see. You need two steps: the organism gone, and then the colour.
Getting mould out of clothes in four steps
The first step happens outdoors, and that is not being overly careful.
- Let the garment dry out completely first and brush it off outdoors. Dry spores brush away, damp ones smear. Outdoors, because you do not want to spread the spores through your house.
- Soak for one to two hours in cold water with oxygen bleach. That is the powder from a box of stain remover, and it bleaches with oxygen instead of chlorine. Lukewarm water at around forty degrees works best.
- Wash as hot as the care label allows. Heat is fine here, because there is no protein in this stain. Sixty degrees also kills off whatever is still alive.
- Dry it in the sun if you can. Sunlight bleaches the remaining colour away further and it costs nothing. Do watch out with coloured fabrics: the sun bleaches the fabric itself as well.
If a shadow is still there, repeat step two. Two or three rounds are normal with stains that have been sitting for weeks.
Why chlorine bleach is usually the wrong choice
It sounds logical and it often goes wrong.
Chlorine bleach kills the mould and takes the colour out, so on white cotton it works. The problem lies everywhere else: on coloured fabrics it leaves a permanent pale patch, and on wool, silk and many synthetics it attacks the fibre. What you are left with is no longer a stain but a hole in the colour.
Oxygen bleach does the same job, only more slowly and without that risk. That is why it sits in step two above and chlorine does not.
And never mix chlorine bleach with vinegar, not even one shortly after the other in the same bucket. That combination gives off chlorine gas.
The home remedies, measured up
Four tips that do the rounds, and what they really do.
Vinegar
Vinegar slows mould growth and it helps against the musty smell. Against the stain itself it does little. As a pre-soak, half an hour in lukewarm water with a generous splash, and then still do step two.
Bicarbonate of soda
Absorbs odour and scours gently. Fine alongside vinegar against the smell, nowhere near enough against the colour.
Lemon juice with salt, in the sun
This old trick really does work on white cotton: lemon juice is acidic, salt scours and the sun bleaches. On white only, and not for hours on end, because coloured fabrics fade along with it and that does not come back.
Hydrogen peroxide
Works, and it is in effect the same principle as oxygen bleach. Test it on a seam first, because this bleaches too. Not on wool or silk.
Mould in places other than clothing
Three situations with a different approach.
A tent or awning. Never in the washing machine, that wrecks the waterproof layer. Brush it off dry, wipe it down with lukewarm water and a mild soap, and then let it dry completely before it goes back into storage. Re-treat the water-repellent layer if it has been damaged.
A mattress. Do not get it wet, because that makes the problem worse. Brush it off dry outdoors, let it dry in the sun, and then use a mattress protector. The bed base and the slats underneath only need a wipe and time to dry, and the right cloth makes that quicker: Which cloth do you use for which cleaning job?
Mould on a wall. That is a different story. Black patches on a wall or in the grout are a damp problem in the building, not in your cleaning routine. You can scrub it away, but it comes back for as long as the damp is there. That calls for ventilation or building repairs.
How to stop it coming back
This is the only part that really solves the problem.
Do not leave anything lying wet. A wet towel in the laundry basket or wet sports kit in a bag is enough within a day or two to get it started. Hang it up until you do the washing.
Take the washing out of the machine straight away. A clean load that sits in the drum for hours smells musty, and that is the same cause.
Do not store anything damp. Tents, sleeping bags, winter coats: bone dry before they go into the cupboard. This is the most common cause of stains you only discover a season later.
Leave the washing machine door open. If your machine itself smells musty, that is where it starts. Cloths and towels that never dry out properly are the usual suspects: How to use and wash microfibre cloths.
Why the granny trick stops halfway, and the bottle does too
With mould the limit lies somewhere other than you would expect.
With most stains you come up against the strength of the product. Not here: the problem is that the product hits the wrong target. A mould-killing product does indeed kill the mould, but the colour it has deposited is still sitting in the fibre.
That is why bleaching works and disinfecting does not, and that is also why the honest message is this: on white it usually goes, on colour often not completely.
And heat is your friend here, unlike with sweat and blood. There is no protein in this stain, so a hot wash is allowed and it helps. On a tent or a mattress you can use steam to kill the spores without soaking the fabric, but steam does not get the colour out either.
What comes back in every case is drying. What is dry does not go mouldy. Cloths for drying off afterwards are under laundry and textile care.
Frequently asked questions
How do you get mould out of clothes?
Let it dry out completely first and brush it off outdoors, then soak for one to two hours in lukewarm water with oxygen bleach, then wash at the highest temperature the care label allows. Drying in the sun helps with the last of the colour. Two or three rounds are normal with old stains.
Do mould stains always come out?
On white cotton they usually do. On coloured or delicate fabrics a shadow often stays, because what you see is not the mould but the dye it has deposited in the fibre. That is the limit, not a question of trying harder.
What is "het weer" in clothing?
That is an older Dutch name for exactly the same thing: the grey or brown spots that appear when textiles have lain damp for too long. Some regions say mould, others say "het weer".
May I use chlorine bleach?
On white cotton you can, but on coloured fabrics it leaves a permanent pale patch and on wool, silk and many synthetics it attacks the fibre. Oxygen bleach does the same job without that risk. Never mix chlorine with vinegar, because that gives off chlorine gas.
Does vinegar help against mould in textiles?
Against the musty smell and against further growth it does, against the stain itself very little. Use it as a pre-soak, half an hour in lukewarm water with a generous splash, and then still do the oxygen bleach step.
Does lemon juice with salt in the sun work?
On white cotton it really does: lemon juice is acidic, salt scours and sunlight bleaches. Only on white and not for hours on end, because coloured fabrics fade along with it and that does not come back.
How do I get mould out of a tent?
Not in the washing machine, that damages the waterproof layer. Brush it off dry, wipe it down with lukewarm water and mild soap, then let it dry completely before storing it. If the water-repellent layer has been damaged, re-treat it.
Why does my washing smell musty when it is clean?
The same cause: the washing has lain damp for too long, in the drum or in the basket. Take the washing out of the machine straight away and hang it up. If the machine itself smells as well, that is where it starts.
Can I get mould out of a mattress?
Only dry: brush it off outdoors and let it dry in the sun. Do not get it wet, because damp in a mattress is exactly the cause. Use a mattress protector afterwards.
Is mould on the wall the same problem?
No. Black patches on a wall or in the grout are a damp problem in the building. You can scrub them away, but they come back for as long as the damp is there. That calls for ventilation or building repairs, not a cleaning product.
Elsewhere in the house
Everything is sorted by job under cleaning products.