How to apply anti mould paint
Updated: 22 October 2026
You have a tin of anti-mould paint, or you are about to open one, and the black spots are still on the ceiling. How to apply anti mould paint is mostly the order of work: kill what is growing, let the surface dry, then two coats, and leave Ronseal's film as the top coat. Painting straight over the spots is the shortcut that brings them back. Which tin to buy stays on the [anti-mould paint comparison](/hub/paints-and-varnishes/anti-mould-paint). Peter F. compared those amazon.co.uk listings, Ronseal's instructions and public UK health pages. We did not run a lab test. A purchase through the comparison can earn us a commission at no extra cost to you.
You have a tin of anti-mould paint, or you are about to open one, and the black spots are still on the ceiling.
You have a tin of anti-mould paint, or you are about to open one, and the black spots are still on the ceiling. How to apply anti mould paint is mostly the order of work: kill what is growing, let the surface dry, then two coats, and leave Ronseal's film as the top coat. Painting straight over the spots is the shortcut that brings them back. Which tin to buy stays on the anti-mould paint comparison. Peter F. compared those amazon.co.uk listings, Ronseal's instructions and public UK health pages. We did not run a lab test. A purchase through the comparison can earn us a commission at no extra cost to you.
Our top picks
| Badge | Product | Dry time | Full cure | Finish | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Zinsser Zinsser Perma-White matt white 2.5 litres | 1 hour | 24 hours | Matt | 9.4 | about £39.53 | View offer |
| Alternative |  Ronseal Ronseal anti-mould paint white matt 750 ml | 2 hours | 2 hours | Matt | 9.0 | about £19.21 | View offer |
| Best value |  Ronseal Ronseal anti-mould paint white matt 2.5 litres | 2 hours | 2 hours | Matt | 9.0 | about £34.19 | View offer |
On this page
Do not paint the live mould
The failed job starts with a brush on the black spots. Ronseal's guide says kill the mould first and do not sand it. GOV.UK and local council pages say the same thing in health language: do not brush or vacuum mould, because that spreads spores. Wipe what the mould killer has treated, using the method on the killer's own label, and keep the room ventilated while you do it. If the patch is above about 1 square metre, if it triggers asthma, or if it is coming from the building or from sewage, an NHS-linked page says get help rather than clean it yourself.
Drying is the step people skip because the wall looks clean. A film laid on a damp patch is sitting on the same water that fed the mould. Ronseal wants the room above 10 °C. One amazon.co.uk review of the 750 ml Ronseal reports mould back after about eight weeks on a wet outside-wall larder. Another, on Polar, reports small patches back after about a month on cold bedroom walls. The prep failed because the wall stayed wet, not because the brush was the wrong size.
Bare plaster and new plaster are a different wait. Ronseal says new plaster should stand for seven days and then take a sealer before this paint. A Zinsser review of bare drywall still needed a sealer and extra coats even though the Perma-White title says self-priming. Read the tin you are holding. If it tells you to seal, seal. The bathroom fan, once the film is on, stays on anti-mould paint for bathrooms.
Two coats and the clock
Two coats are the job, not a tidy extra. Ronseal states two coats, with the second after 4 hours, and 24 hours before you let condensation hit the film. Polar's bullets say touch dry in 2–3 hours and a second coat after 4 hours. Zinsser's amazon.co.uk listing gives a dry time of 1 hour and a full cure of 24 hours. Mould Solve's listing has no dry-time number, so you cannot quote one. Follow the tin. Several call the 750 ml Ronseal thin or runny, and a minority on the 2.5 litre tin needed extra coats before the colour looked even. Stir before you start. Zinsser reviews mention a thorough stir, and a stir stick is in that tin's included items.
A workable day looks like this. Kill and wipe in the morning, leave the ceiling to dry, and stay above 10 °C if the tin is Ronseal. Lay the first coat, wait the recoat time on the label, and lay the second coat once 4 hours have passed. Do not shower that night. Ronseal's 24 hours before condensation still applies when the paint feels touch dry. Several reviews on Zinsser, the 750 ml Ronseal and Mould Solve say it is too soon to score mould resistance after a fortnight. The listing full-cure field on the Ronseal tins says 2 hours. Use the instruction on the can you are holding when that field and the can disagree.
Ronseal's film has to stay on top
Ronseal says you cannot paint ordinary emulsion over its anti-mould paint. The biocide is in that film, and covering it with a coloured coat takes the treated surface out of the room. One reviewer of the 750 ml tin painted their original colour over it after three coats. That is the mistake the instruction is there to stop. If you want a colour, you choose it before you paint: a tint base, an additive in emulsion, or Ronseal's separate clear coat over coloured paint. That clear coat is not one of the five tins in the comparison. The route is on anti-mould paint vs additive.
This rule is Ronseal's. Do not stretch it into a ban on every brand. Wickes notes that some makers, including Zinsser, allow a later decorative coat once the film is dry. That is their summary, not a rule for your tin. Read the can in your hand. If it says the anti-mould coat must stay exposed, leave it exposed. Wallpaper over the finished film hides the surface the product was sold to keep at the face of the wall.
The 750 ml Ronseal listing says Spray in the paint-type field. The product is a liquid tin with a brush. Do not look up an aerosol method for this ASIN. Ronseal's aerosol is a different product. Brush or roller, as the liquid tin describes, after you have stirred it.
When it comes back
If the spots return, separate a wet wall from a film that never got two coats. A return in about eight weeks on a larder wall that stays damp, or within about a month where the source was not painted, is the water still arriving. Another coat on that patch repeats the first failure. Find the leak, the cold bridge or the missing airflow before you open a second tin. A return after you used one thin coat, or after you overcoated Ronseal with ordinary emulsion, is the application. Strip back to the instruction: kill, dry, two coats, and leave that brand's film on top.
Stop and get help when the growth is widespread, when someone is wheezing, or when the work means a new extractor or unsafe work at height. Above about 1 square metre, or mould from the building or sewage, is the NHS-linked threshold for getting help rather than cleaning it yourself.
Common questions
Can I paint straight over black mould?
No. Kill it with a mould killer first, wipe what that product tells you to wipe, and let the surface dry. Ronseal and GOV.UK both reject painting or brushing live mould. A coat on the spots traps the growth and the spores spread while you work.
Should I sand the mould off?
Do not sand it, and do not vacuum it. Sanding and dry brushing spread spores. Use the mould killer's method, then a damp wipe if the label allows it. If the area is large or you have asthma, stop and get help rather than sanding a ceiling.
How many coats?
Two. Ronseal states two coats, with the second after 4 hours. Polar's bullets say the same 4-hour recoat. Reviewers who used one thin coat describe an unfinished colour, and several call the 750 ml Ronseal thin or runny. A third coat of a different paint is not the same thing as the second coat of this one.
How long before I shower or let the bathroom steam?
On Ronseal's instruction, wait 24 hours before condensation, even if the paint feels dry sooner. The listing dry times are shorter: Zinsser cites 1 hour to dry and 24 hours to full cure, and Polar cites touch dry in 2–3 hours. Steam on the first night is the failure. Keep the room above 10 °C while Ronseal is going on.
Can I paint a colour over Ronseal anti-mould paint?
Ronseal says no. Ordinary emulsion over the anti-mould film covers the surface the product is sold to leave exposed. One reviewer did paint their old colour over three coats. That is the case the instruction is there to prevent. Choose a colour system before you start, or follow a different tin if its own label allows a later coat.
What about new plaster?
Ronseal says wait seven days, then seal, then paint. A self-priming title is not a promise that bare drywall needs nothing: one Zinsser reviewer still sealed and used extra coats. If the tin you bought names a sealer, use it.
The spots came back after two months. What failed?
Usually the wall was still wet, or the film never got two proper coats. An eight-week return on a wet larder wall is the water, not a reason to switch brand and paint the same damp plaster. Check for a leak or a cold wet surface first. If you overcoated Ronseal with emulsion, the treated face is no longer the face of the wall.
Related pages
Sources
Public sources from the research digest, last checked on 19 October 2026. Shelf prices and star lines are the amazon.co.uk figures in the display file. Scores are a reading of those listings, not a laboratory test.
- GOV.UK: damp and mould health risks (retrieved 19 October 2026)
- GOV.UK: Awaab's Law for social-housing tenants (retrieved 19 October 2026)
- SI 2025/1042 (retrieved 19 October 2026)
- VOC Regulations 2012, Schedule 2 (retrieved 19 October 2026)
- HSE: biocides and COPR (retrieved 19 October 2026)
- Ronseal: 6 Year Anti Mould Paint (retrieved 19 October 2026)
- Zinsser UK: Perma-White (retrieved 19 October 2026)
- Healthier Together (NHS): damp and mould (retrieved 19 October 2026)