Purple Mold: What It Is on Walls and Wood, and the Look-Alikes

How rare is purple mold? What the sources say

Purple is the thinnest colour in the sources we read. We checked the federal, extension, mycology and pricing sources used on this site and recorded whether each names purple. Two do, one describes a purplish brown slime mold, and the rest do not.

Source	Colours it describes	Names purple?
EPA mold course, chapter 1	Molds come in many colours	No
CDC, Mold	Spots of many different colours	No
Adelaide, Fusarium	Whitish to yellow, pink, red or purple; some complexes pink or vinaceous to violet	Yes
Adelaide, Penicillium	Green tones, sometimes white	No
USDA FPL Wood Handbook ch. 14	Blue stains most common; yellow, orange, purple and red sometimes	Yes, in wood
Arkansas Extension, slime mold	Orange, yellow, green and even blue	No
Stemonitis splendens entry	Sporangia dark purplish brown	Purplish brown
Fixr cost guide	Ten priced types, none purple	No

So purple on a wall is more likely a look-alike than a mold, and when it is mold, colour does not say which. Only a lab can name it; mold testing explains when that is worth paying for.

What you are looking at

The EPA mold course, chapter 1 says molds come in many colours, and the first test for purple is texture. Growth is fuzzy, cottony or powdery and lifts onto a damp towel; product colour, dye and mineral tints are flat.

What you see	Usually	Where	Next step
Fuzzy or cottony growth with a purple or violet tint	Fungus, possibly Fusarium	Damp organic material	Treat as mold
Purple streaks inside sapwood that do not sand off	Fungal stain	Lumber, framing	Cosmetic if dry
Tufts of tiny dark purplish brown stalks on rotting wood	Slime mold (Stemonitis)	Logs, wet wood outdoors	Remove; see orange mold
Flat, even purple paper face on new walls	Mold-resistant drywall	New construction, basements	Leave it
Pink to purple tint in water or a ring in the bowl	Potassium permanganate	Filtered well water	Call the water treatment service
Sharp-edged purple blot, no texture	Dye, ink or wine	Near clothing, toys, spills	Stain removal, not mold work

On the fungus itself, the University of Adelaide description of Fusarium says most species are soil fungi with a worldwide distribution and some are plant pathogens. It records Fusarium oxysporum complex growth as white becoming purple, with a reverse from hyaline to dark blue or dark purple. By contrast, the Adelaide description of Penicillium describes green tones and sometimes white, not purple. The USDA FSIS fact sheet Molds on Food lists Fusarium among molds on foods; its rule is to discard moldy soft foods.

Which purple is this? Six questions

1. Does it have texture? Fuzz or powder that transfers to a damp towel is growth. Why this differs from generic advice: most purple marks indoors are flat, and no mold product removes dye or product colour.
2. Is the whole board face evenly purple? It is drywall paper. Why: National Gypsum’s purple line is purple by design; check the back paper, which its sheet lists as gray.
3. Is it in water from a filtered well? Think permanganate. Why: the fix belongs to the treatment system, not a cleaner.
4. Is it inside wood rather than on it? Purple fungal stain. Why: the FPL says sap stain cannot be removed by surfacing, so sanding chases it through the board.
5. Is it a cluster of tiny stalks on rotting wood? A slime mold. Why: it is not a fungus; it signals wood that stayed wet.
6. None of the above, and the area is damp? Treat it as mold. Why: CDC says the type does not matter for removal.

Purple mold on wall surfaces

Purple mold on a wall is most often not mold, and each surface has a different likely answer. EPA's brief guide to mold and moisture adds that mold may hide behind drywall, wallpaper or paneling.

Wall surface	What you see	What to do	Why
Painted drywall	Purple-tinted fuzz near a leak	Scrub if small and sound; replace soft paper	Colour changes nothing; moisture does
Unfinished drywall, even purple face	Flat colour, printed guide marks	Nothing	Purple face paper is the product
Wallpapered wall	Purple or dark spots coming through	Do not peel casually	EPA warns of a massive spore release
Child’s room, laundry, near fabric	Hard-edged blot	Treat as a dye stain	No growth means no remediation

The Gold Bond XP Hi-Abuse submittal sheet describes a mold and moisture resistant core in purple face paper with gray back paper, and says no material can be considered mold proof. Purple paper is no sign of mold, and a wet purple board can still grow it. Likewise, the USG technical bulletin PM4 says a blue dye identifies plaster base paper.

Spec, according to each maker	Gold Bond XP Hi-Abuse (purple face)	USG Imperial gypsum base (blue face)
Face paper colour	Purple, 100% recycled	Blue (dyed for identification)
Back paper	Gray, mold and moisture resistant	Not stated in bulletin
Mold test (ASTM D3273)	Score of 10, best possible	Not stated
Fungal test (ASTM G21)	Score of 0, best possible	Not stated
Water absorption	Below 5% of weight	Not stated
Colour change in sunlight	Not stated	Fades to grey or yellowish
Manufacturer caveat	No material can be considered mold proof	Avoid excessive moisture

General wall method is on mold on walls; why colour does not mean hazard is on black mold vs regular mold.

Purple mold on wood

The USDA Forest Products Laboratory Wood Handbook, chapter 14 says the so-called blue stains are the most common fungal stains in wood, although various shades of yellow, orange, purple and red are sometimes encountered, and that the exact colour depends on the organism and the species and moisture condition of the wood. Like blue stain, the FPL says typical sap stain penetrates the sapwood and cannot be removed by surfacing.

On the wood	Likely cause	Check	Action
Purple streaks or wedges inside sapwood	Fungal stain	Sand a corner: colour continues	Cosmetic if kept dry
Purple-tinted fuzz on the surface	Mold	Wipes or brushes off	Clean and dry; see mold on wood
Tufts of stalks 10 to 20 mm tall on rotting wood	Slime mold (Stemonitis)	Touch releases brown spores	Remove; fix the wet wood
Pink patch on oak after oxalic acid	Chemical stain from the treatment	Appears after bleaching	Rinse promptly next time
Blue-black or grey halo at nails	Iron stain	Oxalic acid clears it	See blue mold
Soft wood under any colour	Decay	Probe with an awl	Structural review

The slime mold row is the purple most likely to be found on wet wood outdoors. Wikipedia's Stemonitis splendens entry, citing Young's Field Guide to the Fungi of Australia describes the chocolate tube slime as clusters on sheltered, decaying wood, with sporangia dark purplish brown, 10 to 20 mm tall and 1 to 2 mm across, on black stems. Washington State University Extension advises scooping slime mold into a bag rather than hosing it; handling is on orange mold.

One pink look-alike is self-inflicted. According to the FPL note Iron Stain on Wood, oxalic acid clears iron stain but can leave a pink stain on oak if left too long; it calls for at least 5% by weight and a warm water rinse. Moisture decides whether a fungus spreads: according to the USDA Forest Products Laboratory Wood Handbook, chapter 14, the fiber saturation point averages 30%, and air-dried wood at 20% or less has a reasonable margin of safety.

Purple in sinks and toilets

A purple ring in a toilet or sink on a private well is usually chemistry. Penn State Extension describes manganese greensand filters that need frequent regeneration with a potassium permanganate solution. The Town of Blades, Delaware warned residents in October 2016 of light pink or purplish water for a few days after filter testing sent extra permanganate into the supply. If the colour follows a filter service, call the treatment company.

Minerals give other colours, and EPA's secondary drinking water standards name them. Copper above its secondary level causes blue-green staining, iron causes reddish or orange staining, and manganese causes black to brown colour and black staining; EPA does not enforce these levels. Pink film is a separate question, answered on pink mold and red mold.

What to do for each

Cause	Method	Why this differs from generic advice
Purple-tinted mold on hard surfaces	Detergent and water, dry completely, per EPA	The colour does not change the method
Purple-tinted mold on porous materials	Bag and remove	EPA says porous materials may have to be thrown away
Purple fungal stain in wood	Dry it; seal or leave	Sanding chases a stain the FPL says goes into the sapwood
Slime mold on wet wood or mulch	Scoop into a bag, per WSU; dry the area	Not a fungus; mold products are beside the point
Purple drywall face	Nothing	It is the product
Permanganate tint in water	Treatment company service	The source is the filter, not the fixture
Dye, ink or wine	Stain removal for that material	No growth, no remediation

For true mold, the EPA's brief guide to mold and moisture treats areas under about 10 square feet as a do-it-yourself job, says to dry wet items within 24 to 48 hours and keep humidity below 60 percent. Steps are on DIY mold remediation.

Signs it is bigger than the spot

What you see	What it usually means	Next step
Purple growth back within weeks of cleaning	The moisture source is still active	Find and fix the water
Purple spots showing through wallpaper	Growth on the paper back or drywall	Scope containment first
Slime mold indoors on framing or a subfloor	Wood wet long enough to decay	Probe; moisture readings
Purple drywall that is soft, stained or swollen	Water damage despite the mold-resistant board	See mold on walls
Purple tint that returns after every filter service	Permanganate feed or rinse problem	Water treatment provider
Growth larger than about 10 square feet	Beyond EPA homeowner scale	Professional scope

For contractors

Purple is a scoping trap both ways. A purple board face can be logged as growth, and real growth on it dismissed because the board is mold resistant. Document the board, the water and the texture.

Document	Why it belongs in the file
Wipe test and close-up photo	Separates growth from dye and product colour
Board make and face colour	Purple face paper is not a finding
Water source and any treatment system	Routes permanganate to the treatment trade
Moisture content of stained wood	Against the FPL 30% and 20% lines
Lab result, if the owner wants a name	Colour cannot identify the organism
Measured area of true growth	Against EPA’s 10 square foot line

According to Fixr, remediation averages $3,500 nationally; see mold remediation cost. On claims, the ISO HO 00 03 sample form hosted by the Insurance Information Institute excludes mold, fungus or wet rot, with a give-back for such loss hidden within walls or ceilings or beneath floors when it results from accidental discharge or overflow from a plumbing, heating, air conditioning or sprinkler system, or a household appliance. An adjuster asks for the water source and timeline. What a given policy pays depends on its form and endorsements, so the owner’s policy, their state insurance department and a licensed professional decide.

Questions people actually ask

What is purple mold?

A colour description, not a species. The University of Adelaide says Fusarium colonies can range from whitish to yellow, pink, red or purple, and the USDA Forest Products Laboratory says fungal stains in wood are sometimes purple. Many purple marks indoors are not mold: drywall paper, dye, ink or well filter permanganate.

Is purple mold dangerous?

This page does not assess health effects; CDC, EPA and NIH publish that guidance. EPA says no one can tell whether a mold is producing mycotoxins just by looking at it, and CDC says you do not need to know the type to remove it.

Why is there purple mold on my wall?

First check it is mold. If the whole board face is evenly purple, it is likely mold-resistant drywall; Gold Bond’s XP sheet describes purple face paper. If it is fuzzy and near a leak, it is growth on damp paper or paint. EPA notes mold can also hide behind wallpaper.

What is purple mold on wood?

Usually a fungal stain or a slime mold. The USDA Forest Products Laboratory says sap stains are mostly blue but sometimes purple, and that they penetrate the sapwood and cannot be surfaced off. Tiny dark purplish brown stalks in clusters on rotting wood are likely a slime mold such as Stemonitis.

Is purple mold rare?

Yes, by the published record. Of the federal, extension, mycology and pricing sources checked for this page, only the Adelaide Fusarium description and the USDA Forest Products Laboratory name purple directly. Fixr prices ten mold types and none is purple. Most purple sightings indoors turn out to be look-alikes.

How do I get rid of purple mold?

Identify it first. For real mold, EPA says scrub hard surfaces with detergent and water and dry completely, discard moldy porous materials, and fix the water within 24 to 48 hours. Leave purple drywall paper alone, call the water treatment provider about purplish water, and scoop slime molds into a bag.

Why is my water purple or pink?

On a filtered well, the usual cause is potassium permanganate, the chemical used to regenerate greensand filters. The Town of Blades, Delaware traced light pink or purplish water to extra permanganate during filter testing in 2016. It is not mold. Call the treatment provider, and see our pink mold page for pink film.