Mildew Remover: Methods by Surface, From Grout to Boat Vinyl

Search results for this term are product grids. A grid cannot tell you that the cleaner that brightens grout is wrong for a vinyl boat seat, or that a library tutorial says to keep liquids off moldy books. This page sorts the job by material, from labels, extension services, the USDA Forest Products Laboratory, a university library and fabric makers. For what mildew is, see mold vs mildew; for kill claims and contact times, see our mold killer label guide.

Growth and stain are two jobs

Mildew sits on the surface. The Forest Products Laboratory GTR-109 says mildew fungi on wood live only on the surface, do not tunnel into it and do not reduce its strength; they are objectionable because they discolour it. That is why removal comes in two steps: get the growth off, then decide what to do about the colour it left.

Registered products say the same. The Concrobium label warns that mold stains may remain visible after treatment, that staining may be irreversible in some cases, and not to expect it to whiten stains.

What you see	What it usually is	First move	Source
Fuzzy or powdery growth on the surface	Living or dormant growth	Brush or vacuum off, then clean	UF/IFAS, Cornell
Dark spots left after cleaning	Stain left in the material	An oxidizer suited to the material	Tilex, UF/IFAS
Uniform gray on bare wood	Commonly mildew, per USDA	Bleach solution or a wood brightener	FPL GTR-109
Blue-black marks around nails on wood	Iron stain, not mildew	Oxalic acid	FPL GTR-109
Pink stain on vinyl or plastic	Pigment from microorganisms	Prompt cleaning; prevention	MasterCraft, EPA PPLS

The chemistries that lift mildew stains

Three oxidizer families do most stain removal. Chlorine bleach is the strongest decolouriser; household bleach is a 5% sodium hypochlorite solution, per the Forest Products Laboratory GTR-109. Oxygen bleaches act more slowly: PubChem lists sodium percarbonate as disodium carbonate with hydrogen peroxide, and the UGA and UF/IFAS guides offer sodium perborate or powdered non-chlorine bleach where chlorine is unsafe.

Chemistry	Where the sources use it	Where not	Source
Chlorine bleach (sodium hypochlorite)	Mildew stains on tile, grout, colourfast canvas, painted exteriors, bare wood	Silk, wool, spandex; fabric, carpet, paper, aluminum per Tilex; boat vinyl per MasterCraft	UF/IFAS, Tilex, MasterCraft
Oxygen bleach (sodium perborate, percarbonate)	Washable fabric that cannot take chlorine; old stains soaked overnight	UF/IFAS soak: 30 minutes or longer	UGA, UF/IFAS, PubChem
Hydrogen peroxide, 3%	Carpet, as 1 part to 5 parts water	Test colour first	UGA
Oxalic acid	Iron stain and graying on bare wood, as a brightener	Toxic; keep off skin and plants	FPL GTR-109
Diluted alcohol, 1 to 1	Leather, upholstery, mattresses	Damages acetate, triacetate, modacrylic and acrylic fibres	UF/IFAS, UGA

Oxalic acid is the outlier. The Forest Products Laboratory names it for iron stain, the blue-black mark tannins form with iron, at 1 to 4 oz per quart of hot water, and as one way to brighten weathered wood. It is not a mildew remover.

How to remove mildew, surface by surface

This is the table to keep. Each row is the method published by the source named; follow its label or guide for the full directions, and spot test anything coloured first.

Surface	Method	Source	Do not
Shower grout	Spray a label-listed product, wait until stains disappear, rinse	Tilex, Crescent	Old grout may hold stains the product cannot reach
Silicone caulk	Same label direction	Tilex, Crescent	Labels say embedded mildew may not come out
Vinyl shower curtain	Label-listed spray, rinse promptly	Crescent lists vinyl curtains	Rinse vinyl immediately
Fabric curtain, clothing	Brush outdoors, sun, then lemon and salt, oxygen bleach or 2 Tbsp chlorine per quart	UF/IFAS	No chlorine on silk, wool, spandex
Upholstery, mattress	Vacuum, then 1 cup alcohol to 1 cup water; dry well	UF/IFAS, UGA	Alcohol damages acetate and acrylic fibres
Leather	Diluted alcohol 1 to 1, air dry, then saddle soap and polish	UF/IFAS	Test colourfastness first
Books and paper	Dry with moving air; HEPA vacuum once dry; work outdoors or in a hood	Cornell	No bleach or cleaning agents on books
Painted siding	Registered house wash mixed with bleach, wait, rinse	Mildew Check, Jomax	Pretest; cover plants
Bare wood deck	Bleach 1 to 3 with some detergent, rinse, 2 warm windy days to dry before finishing	FPL	No liquid or ammonia detergent; keep the silver fibres
Boat canvas	1 cup bleach, 1/4 cup dish liquid per gallon, 15 min, rinse	Sunbrella	For Sunbrella fabric
Boat vinyl seats	Soft brush, warm soapy water, rinse, dry	MasterCraft	Bleach is on its not recommended list

Grout, caulk and shower curtains

The Tilex label directs: spray, wait until stains disappear and rinse; heavy buildup may need two cleanings, and mildew embedded in old grout or silicone caulking may not come out. Rinse rubber, plastic and vinyl immediately, it says, and keep it off fabric, carpet and paper. The Crescent label lists vinyl curtains among its surfaces. When a joint stays dark after two cleanings, the fix is the joint itself; see mold in shower.

Fabric, upholstery and leather

UF/IFAS Extension starts every fabric with brushing outdoors and sun. For washables it offers lemon juice and salt, powdered non-chlorine bleach at 1 to 2 tablespoons per pint soaked 30 minutes or overnight, or chlorine bleach at 2 tablespoons per quart for 5 to 15 minutes. Leather gets 1 cup denatured alcohol to 1 cup water, drying in moving air, then saddle soap.

Painted siding and decks

Per the Mildew Check label, mix 5.5 parts product to 1 part fresh 5.25% bleach, pretest 20 minutes for colour and adhesion, and discard the mix after 2 hours. The Jomax label limits its bleach wash to exterior painted, non-porous surfaces, 5 minutes then rinse. For bare decks, the Forest Products Laboratory deck guide gives bleach with 3 parts water and some detergent, warns against liquid or ammonia detergents, and says not to scrub off the silver fibres left by weathering, because they absorb stain well. For structural wood, see mold on wood.

Books, paper, boats

Cornell University Library says chemical treatment is no longer viewed as effective for moldy books and advises against spraying or swabbing them with bleach or cleaning agents. Dry them with moving air, freeze to stabilise if needed, then HEPA vacuum once dry, wearing N95 masks and gloves. UF/IFAS, by contrast, suggests a bleach solution for stubborn paper stains; for anything of value, follow the library guidance. On boats, Sunbrella allows bleach on its canvas, while the MasterCraft vinyl care page lists bleach as not recommended for vinyl and says never to cover wet vinyl.

Published bleach recipes disagree, by a lot

The bleach share in published recipes spans roughly 8-fold. According to the quantities printed, the UF/IFAS clothing recipe is about 3% bleach by volume; the UGA fabric soak and both Forest Products Laboratory wood recipes are 25%. We could not reconcile the two fabric recipes, so start with the more dilute one and spot test.

Source and use	Bleach	Water	Bleach share
UF/IFAS, clothing	2 Tbsp	4 cups	3%
UF/IFAS, painted interior walls	0.75 cup	16 cups	4.5%
Sunbrella, boat canvas	1 cup	16 cups	5.9%
UF/IFAS, bathroom and basement	4 cups	36 cups	10%
UGA, washable fabric soak	0.25 cup	0.75 cups	25%
FPL decks, 1 part to 3 water	1 cup	3 cups	25%
FPL GTR-109, wood	4 cups	12 cups	25%

Registered mold and mildew removers, and their directions

A mold and mildew remover that also claims to kill or control growth is a pesticide and carries an EPA Reg. No. Not every mildew spray does. The RMR-86 safety data sheet, for a hypochlorite stain remover, describes its use as removal of mold stains and mildew stains and shows no EPA registration number in its regulatory section.

Product	EPA Reg. No.	Active and %	Stain direction	Surfaces
Tilex Mold & Mildew Remover	5813-24	Hypochlorite 2.4%	Spray, wait until stains disappear, rinse	Bath surfaces; not wood or painted (optional text)
Crescent Mold & Mildew Remover	68777-3	Hypochlorite 2.40%	Spray, penetrate, wipe, rinse	Grout, tile, vinyl curtains; not wood or painted
Mold Armor Killer + Quick Stain Remover	4091-23	Hypochlorite 4.0%, carbonate 1.0%	Apply, wait 10 min, rinse	Hard non-porous; rinse vinyl within 15 min
Jomax House Cleaner and Mildew Killer	69587-1	o-Phenylphenol, sodium salt 0.25%	Mix with bleach and water, 5 min, rinse	Exterior painted siding, decks; not interior
Mildew Check Multi-Purpose Wash	56601-2	IPBC 0.23%	5.5 parts to 1 part bleach, no water	Siding, decks, stucco, brick
Wet & Forget	84115-1	Quat 9.9%	13 oz per 5 gal, 10 min, air dry	Siding, decks, roofs
Concrobium Mold Control	82552-1	Sodium carbonate 0.95%	Apply, wipe, dry; does not whiten	Wood, wallboard, fabric

Outdoor products are slow by design. The Wet & Forget label says growth or stains may take 6 to 12 months to come clean in the worst case, and that cedar or redwood decks may need brushing.

When the stain outlives the growth

A stain that survives cleaning is not proof the mildew is still alive. Several sources say plainly that some colour stays: the Concrobium label says staining may be irreversible, Cornell University Library says stains near a book’s joints, head and tail are unlikely to be fully removed, and the Forest Products Laboratory GTR-109 warns that wood left unfinished for several years may not regain its colour.

What you see	What the source says	Next step
Dark grout or caulk after two cleanings	Embedded mildew may not come out, per Tilex	Replace the joint
Spots on fabric after one bleach soak	Old stains may need an overnight soak, per UF/IFAS	Oxygen bleach overnight if the fibre allows
Shadow on paper near the spine	Cornell: unlikely to be removed	Accept it, or consult a conservator
Deck still silver after cleaning	Empty fibres, per FPL; colour may not return	Leave them; they take stain well
Faint mark after a fungistat	Concrobium: does not whiten	Follow with a stain remover suited to the surface
Siding still streaked after an outdoor wash	Wet & Forget: up to 6 to 12 months	Wait before re-treating

If dark growth comes back, it is a moisture problem. EPA recommends keeping indoor humidity below 60 percent, ideally 30 to 50, per EPA's Brief Guide to Mold.

Mixing and material rules

The Crescent label names the combinations that release hazardous gases with bleach: ammonia products, toilet bowl cleaners, rust removers, vinegar and acids. Oxalic acid is an acid, so keep it and bleach apart. The Forest Products Laboratory deck guide adds that the detergent in a bleach wash must not contain ammonia, and EPA’s brief guide gives the same bleach and ammonia warning. Bleach hazards in full are on our does bleach kill mold page.

Protect what is nearby: the Mildew Check label says to wet and cover shrubs, rinse them after, and keep the solution off clothing, lawn furniture and cars.

For contractors

Mildew stain work sits between cleaning and remediation, and the scope should say which. Surface growth on non-porous material is a cleaning task; EPA's homeowner cleanup page notes porous items such as carpet and ceiling tile may have to be discarded. Write stain treatment as a separate line with a stated outcome, because the labels themselves concede that some stains are permanent.

What to scope or record	Why
Stain treatment as its own line item	Labels say staining may persist after growth is gone
Spot test record per material	Every guide here requires a colourfastness test
Product and EPA Reg. No. used	Ties the work to a public label
Porous items listed for disposal	EPA: porous materials may have to be thrown away
Contents sent out: books, leather, textiles	Methods differ by material, per the sources above
Moisture source and humidity reading	Stains return where moisture does

Questions people actually ask

Does vinegar actually kill mildew?

Vinegar carries no EPA registration, so no vinegar bottle can make a registered claim to kill mildew. UGA Extension does include white vinegar with washing soda in a wash for light mildew on tile and glass, as a cleaner. Our vinegar page covers what the studies found; for heavy staining, an oxidizer does the colour work.

Is mildew the same as mold?

Mildew is a fungus. The USDA Forest Products Laboratory describes mildew on wood as stain fungi, different from decay fungi, that live only on the surface and do not weaken it. Our mold vs mildew page explains the terms; the cleanup depends more on the material than on the name.

What do professional mold removers use?

On cleanable surfaces, mostly detergent, physical removal and drying, because EPA guidance puts removal ahead of biocides. Registered products are used where judgement calls for them, and each must be used as its label directs. Stain removal comes after, with an oxidizer matched to the material, and porous items may be discarded instead.

What kills mold permanently naturally?

Nothing does, natural or not. Sun and air drying are the first step for fabrics in the UF/IFAS guide, and lemon juice with salt is its non-bleach stain option, but growth returns wherever a surface stays damp. EPA’s long-term answer is moisture control: indoor humidity below 60 percent, ideally 30 to 50.

How do you remove mildew from a fabric shower curtain?

Brush the growth off outdoors and let it air in the sun, then treat what is left with lemon juice and salt or a non-chlorine bleach soak, per UF/IFAS. Use chlorine bleach only if the fabric tolerates it, at 2 tablespoons per quart of warm water for 5 to 15 minutes, then rinse and launder.

Is a mold and mildew spray safe on boat seats?

Usually not a bleach one. MasterCraft lists bleach as not recommended for its vinyl upholstery and advises a soft brush with warm soapy water, rinsing and drying. Sunbrella allows a bleach and dish liquid mix on its canvas. The Tilex and Crescent labels say to rinse vinyl immediately after contact.