Asking what kills mold on fabric is the right question, and the answer is that several things do, in different ways, on different materials. The differences are the whole point. This is a comparison of the treatments themselves, what each one is, how long it needs, which fabrics and colours it suits, and where each of them stops working.
What actually kills mold on fabric, and what it leaves behind
Every agent that kills mold on fabric is doing two separate jobs at once, and it helps to keep them apart in your head.
The first is stopping the growth. The second is removing what the growth left behind, which is pigment and smell.
Most products are good at one and mediocre at the other. Vinegar deals with smell well and staining badly. Chlorine bleach deals with staining and does nothing at all for fibre strength.
None of this is a health treatment and none of it should be described as one. What these agents do is stop growth, remove a smell, and lift a mark out of cloth.
Three variables decide the result more than the choice of product does. Concentration, contact time, and temperature. Most failures are a perfectly good product given twenty minutes when it needed four hours.
White vinegar
Ordinary distilled white vinegar is dilute acetic acid, usually around five percent in the bottle.
It works by dropping the pH of the surface far enough that growth does not continue, and it breaks down a good deal of what causes the smell.
Dilution is one part vinegar to three parts warm water for a soak, or roughly a cup poured straight into the wash.
Contact time is an hour in a soak, and longer for anything that has been damp for more than a few days.
It is good on every colour, nearly every fibre, surface growth and smell. It is the safest of everything that kills mold on fabric and the one to reach for on something you cannot test.
Where it stops is heavy pigment staining. Vinegar will leave a shirt smelling clean and still marked, and people read that as failure when it is really a division of labour.
Never combine it with chlorine bleach, and keep it off natural stone surfaces while you are working.
Borax
Borax is sodium borate, a powdered alkaline mineral salt sold for laundry use.
It raises pH sharply, which is what suits it to established growth that vinegar has not shifted.
Use about half a cup dissolved in hot water for a soak, and it does have to dissolve. Undissolved granules do nothing except leave grit in the weave.
Give it several hours, and it takes overnight without complaint.
It is strong on cotton and linen, on towels, sheets and heavier household textiles, and on a smell that has settled in.
Where it stops is protein fibre. Alkali damages wool and silk, so keep borax well away from both.
Wear gloves with it, keep it away from children and pets, and rinse the item thoroughly afterwards because it leaves a residue if you do not.
Oxygen bleach
Oxygen bleach is sodium percarbonate, a white powder often sold as colour safe bleach or as a laundry booster.
Dissolved in water it releases hydrogen peroxide, which oxidises the growth and the pigment it left behind at the same time.
That double action is why it is the best all round choice for coloured fabric with visible marks. It is the one product that kills mold on fabric and lifts the mark in the same soak.
Use warm water rather than cold, warm enough that you would call it hot tap water rather than tepid. In cold water it barely activates and people conclude it does not work.
Give it hours. Four as a minimum, overnight for anything established. This is the product most often under-used by a factor of ten.
It loses strength once mixed, so make it fresh each time rather than keeping a bucket going for two days.
Keep it off wool and silk for the same reason as borax, and test on a hidden seam on anything with a deep dye.
Hydrogen peroxide
This is the ordinary three percent bottle from a pharmacy, and it is the same oxidation as oxygen bleach delivered faster and in a smaller quantity.
Apply it directly to a small patch, leave it ten to fifteen minutes, then rinse it and wash the item.
It suits small isolated spots, white and pale cotton, and any situation where you want a quick answer without mixing a bucket of anything.
Where it stops is dye. It lightens a fair number of them, so test on an inside seam and let the test area dry completely before judging it.
Keep it in its dark bottle. It breaks down in light, and an old bottle that has sat in a bright bathroom may be little more than water by now.
Chlorine bleach
Sodium hypochlorite, the standard household bottle, and the one people reach for first and should reach for last.
It is strong oxidation that removes growth and colour together, without distinguishing between the colour you want and the colour you do not.
It has a real use, which is white cotton and white linen, used dilute, as a final step on a mark that has survived everything else.
Everywhere else it is the wrong tool. It strips dye from colours, damages wool and silk, and yellows several synthetics rather than whitening them.
The larger objection is fibre strength. It weakens cellulose, and on material already weakened by growth that is precisely the wrong direction to travel.
It is also poor value on smell. People reach for it expecting the odour to disappear and find that it has not.
Rubbing alcohol
Isopropyl alcohol, usually seventy percent, and its value here is that it evaporates fast.
Fast evaporation means it carries almost no water into the material, which is the entire reason it appears on this list.
Mix equal parts alcohol and water, wet a cloth, wring it until it is barely damp, wipe the affected area and dry it immediately with a second cloth.
It suits leather, painted and finished surfaces, the inside of a bag or a case, and anything that must not get properly wet.
Where it stops is oils. It strips them, so leather needs conditioning afterwards or it stiffens and cracks later.
Test first because it affects some finishes and some dyes, and keep it away from any flame while it is evaporating.
Sunlight and ultraviolet
Daylight genuinely kills mold on fabric rather than only airing it out, and the ultraviolet part is what does the work.
Ultraviolet damages growth on an exposed surface, which is why the sunny side of anything left outside comes back visibly cleaner than the shaded side.
It lifts residual smell in a way a tumble dryer does not, and it costs nothing at all.
Give it several hours and turn the item at least once, because only the face pointing at the sky is being treated.
It penetrates almost nothing. Sunlight treats the surface of a cushion and does nothing whatsoever to the middle of it.
Long exposure fades strong colours, so this is a treatment for something recovering rather than a weekly habit.
Heat, and what it can and cannot do
Hot water helps and it is not the thing that kills mold on fabric on its own. It improves how detergent and oxygen bleach perform, and it speeds everything else up.
Use the hottest water the care label allows. Where the label says cold, add time by soaking longer instead.
Dryer heat is a different matter entirely, and this is where garments are lost. Heat sets a mold stain permanently.
So heat is useful in the wash and dangerous in the dryer, right up until the fabric looks clean while it is still wet.
Ironing carries the same risk for the same reason, so check the area before pressing anything.
Once the mark has genuinely gone, drying heat becomes useful again, because getting the item completely dry quickly is what stops the whole thing recurring.
What does not work
Nothing in this section kills mold on fabric, and all of it gets tried first anyway.
Ordinary detergent on a normal cycle. It lifts soil rather than growth, and it is exactly why the smell keeps returning after the third wash.
Fabric softener and scented products. They coat the fibre, mask the smell for a day or two, and delay you doing the thing that would have worked.
Bathroom mold sprays. They are formulated for tile and grout, several contain bleach that will mark cloth, and none of them are designed to rinse back out of a weave.
Freezing. It suspends growth for as long as the item is frozen and changes nothing once it warms back up.
Baking soda on its own. It absorbs odour without touching what is producing the odour, which makes it a reasonable finishing touch and a useless treatment.
A hot dryer as the first move, which is the most expensive mistake on the list, because it is the only one that cannot be undone.
Contact time is the variable nobody adjusts
When a treatment fails, the usual reason is that it was not given long enough to do anything.
Twenty minutes is a rinse. Four hours is a soak. Overnight is what established growth actually needs.
Keep the item submerged rather than floating. Something clean and heavy on top, or a lid, holds it under.
Warm the water at the start rather than partway through. A soak that cools down is normal. A soak that started cold never really began.
Change the solution and repeat rather than stretching one soak out indefinitely. A saturated soak has stopped working long before you come back to it.
The safety part, and it is short
Never mix chlorine bleach with vinegar. The combination releases chlorine gas.
Never mix chlorine bleach with ammonia or with any cleaner containing it, for the same reason.
If you have soaked something in vinegar and then decide on bleach, rinse the item completely and empty and rinse the container too. Residue counts.
Work with a window open or outdoors, and use one product at a time. Combining two treatments almost never improves either.
Wear gloves for borax, peroxide and bleach, and keep all of it out of reach of children and pets.
Store everything in its own labelled container. Two clear liquids in two unmarked jars is how the mixing accident actually happens.
Matching the agent to the situation
Everything that kills mold on fabric suits one situation better than the others, so here they are side by side.
Coloured clothing with visible marks. Oxygen bleach, warm water, overnight, then a hot wash.
Towels, sheets and heavy cotton with a strong smell. Borax dissolved in hot water, several hours, then the hottest wash the label allows.
Anything you cannot test, or a fabric you are unsure about. Diluted white vinegar, an hour, then wash normally.
A small spot on white or pale cotton. Hydrogen peroxide applied directly, fifteen minutes, then wash.
Wool or silk. Diluted vinegar only, no soaking, no alkali, and a professional cleaner if the item is worth anything.
Leather or anything that must not get wet. Alcohol and water on a barely damp cloth, dried immediately, conditioned afterwards. White cotton with a mark that has survived everything. Dilute chlorine bleach as a final step, accepting what it costs in strength.
Test before you commit
Every agent here affects some dye somewhere, and thirty seconds of testing prevents the outcome nobody wants.
Find an inside seam, a hem allowance, the inside of a pocket, or the tail of a shirt.
Apply the treatment at full working strength rather than a weaker version of it. A weak test tells you nothing about a strong soak.
Wait until the test area is dry before judging it. Wet cloth reads darker and hides a colour change completely.
Do this even with vinegar. It is the mildest thing on the list and it still moves some dyes, particularly on silk and on cheap dark cotton.
The Vancouver part
Two things about this part of the Pacific Northwest change how these treatments get used. The first is the length of the wet season. For much of the year outdoor drying is not a real option, and daylight as a finishing step is available in a narrow window rather than whenever you happen to need it.
That shifts the weight onto the products and onto indoor drying. Oxygen bleach earns its place here because it works in a bucket regardless of what the sky is doing, and a dehumidifier or a fan does the job the sun would otherwise have done.
The second factor is the water itself. Water in this region is naturally soft, and softness changes the arithmetic on every product listed above. Nothing is being consumed by dissolved minerals before it reaches the cloth, so a given amount goes further and a full dose is usually more than the job needs.
The practical version is to start at the low end of whatever the pack recommends and add time instead of powder. Excess product in soft water rinses away poorly and leaves a film in the fibre, and film holds damp, which is how the whole thing started.
Where a long soak turns into a proper wash
Whatever you soak something in, it still needs a wash of its own afterwards with enough water to carry the treatment and everything it lifted out of the weave.
The machines at our self-service laundry on Northeast Vancouver Mall Drive move far more water per cycle than a home unit, which is what rinses a treated item properly instead of leaving product and loosened pigment sitting in the weave, and the larger drums let a heavy soaked item tumble freely rather than turning as one wet lump.
Our machines and the store are cleaned daily.
Our wash-dry-fold service covers the everyday laundry.
For general guidance, The American Cleaning Institute publishes a stain removal guide that is a useful cross-check.
The short version
What kills mold on fabric is not one product. White vinegar diluted one to three is the safe general choice on colours and on smell, and it does little about staining. Borax in hot water suits towels and heavy cotton and must be kept off wool and silk. Oxygen bleach in warm water for four hours or overnight is the best all round option for coloured fabric with visible marks. Hydrogen peroxide is fast on small pale patches and lightens some dyes. Chlorine bleach is for white cotton only and costs fibre strength. Alcohol handles surfaces that cannot get wet. Daylight finishes it. Never mix bleach with vinegar or ammonia.
WaveMAX Vancouver is at 8109 NE Vancouver Mall Drive, easy to reach from Vancouver and the surrounding area. If you have bedding that will not fit at home, call us at 360-433-9864.