# Why is my paint bubbling?

Canonical: https://colorswatchlab.com/guides/why-is-paint-bubbling/
Author: Color Swatch Lab Editorial Team
Published: 2026-10-30
Updated: 2026-10-30
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> Paint bubbles come from one of three things, and you can tell them apart by when they appeared and how deep they go. Tiny bubbles and pinholes that form while you roll are foam: air worked into the wet paint by shaking or fast mixing, rolling too fast, the wrong roller nap or a porous surface. Blisters that rise a few hours to a day or two after painting, only in the top coat and usually on a sunny side, are heat blisters. Blisters that go through every coat down to the wood or drywall, near joints, end grain, a leak or a shower, are moisture blisters. No paint fixes those until the water is stopped. Slice one open to see which you have. The repair always follows the same order: let it dry, scrape, sand the edges smooth, fix the cause, prime bare spots, then repaint.

## Slice one open before you do anything else

A bubble is a spot where the paint film has lost its grip on what is under it, or where gas or air was trapped inside it. The cause decides the repair, so the first job is diagnosis, not scraping. Pick a blister in an out-of-the-way place, cut it with a utility knife and look at the bottom. If you see an older coat of paint, the problem is in the newest coat. If you see bare wood, drywall paper or plaster, the problem is coming from underneath. Purdue University’s extension bulletin on paint failures draws exactly this line: temperature blisters occur only in the last coat of paint, while moisture blisters “usually include all paint coats down to the wood surface.” Also notice whether the blister has water in it. Purdue says moisture blisters contain moisture when they form and then dry and collapse.

| What you see | When it appeared | Likely cause | What fixes it |
| --- | --- | --- | --- |
| Pinholes, small craters, a foamy texture | While rolling or brushing | Air worked into the paint | Change technique or tools; sand and recoat once dry |
| Blisters in the top coat only, older paint under them | Hours to about two days later, often in sun | Heat: the surface skinned over before solvent escaped | Scrape, sand, spot paint; paint out of direct sun |
| Blisters down to bare wood or drywall, may hold water | Days to months later, often in one area | Moisture moving through the wall | Stop the water first, then scrape, dry, prime, paint |
| Bubbles on fresh latex after dew, fog or rain | The first night or so | Moisture before the film had dried | Wait a day or two; repair only if they stay |

## Foam and pinholes while you paint

Bubbles that appear in the wet film are not blisters. Sherwin-Williams lists the usual causes: shaking a partly full can, mixing with a drill at too high a speed, rolling too fast, using a roller nap that is wrong for the surface, putting a gloss paint over a porous surface, and painting in high heat. Behr’s problem solver adds old latex paint (it suggests avoiding paint more than a year old) and low-quality paint. Behr also says that better paints let the bubbles break while the film is still wet, which is why foam sometimes disappears on its own within a minute or two.

If the bubbles are still there once the paint dries, Sherwin-Williams’ fix is to let it dry, sand the area smooth and repaint. Prevention is mostly technique. Stir rather than shake, roll at a steady pace without spinning the roller, and match the nap to the surface. Sherwin-Williams gives 1/4 to 3/8 inch for smooth walls and 3/4 inch or more for textured ones, and Behr suggests a short nap for gloss paints. Prime porous surfaces such as new drywall, patches and bare wood first, so the topcoat does not pull air out of the surface as it soaks in. Roller choice is covered in our [roller and roller cover guide](https://colorswatchlab.com/gear/paint-rollers-and-roller-covers-guide/).

## Heat blisters: the sunny side, the top coat

A heat or temperature blister forms when the outer skin of fresh paint dries before the solvent under it has left. Purdue’s bulletin describes the sequence: a skin forms, then the sun heats the surface and the trapped solvent vaporizes, pushing the skin up. It says these blisters appear a few hours to one or two days after painting, only in the last coat, and are usually seen with oil-based paint. Dark colors, which absorb more heat, and thick coats are more likely to blister. Sherwin-Williams lists the same cause: painting in direct sun on a warm surface. Benjamin Moore’s exterior temperature guide says that painting when it is too hot can cause blistering and peeling.

The prevention Purdue gives is to “follow the sun around the house.” Paint the north side early in the morning, the east side late in the morning, the south side well into the afternoon, and the west side late in the afternoon. It also says to stop at least two hours before the film would cool to the point where dew forms. That timing and the dew-point rule are covered in our [exterior painting weather guide](https://colorswatchlab.com/guides/exterior-painting-weather/). For heat blisters that already formed, Purdue’s repair is to let the paint dry for a few days, scrape off the blisters, sand the edges, and spot paint. Because the older coats under them are sound, you do not need to strip the whole wall.

## Moisture blisters: water from behind the paint

A blister that goes all the way to the wood, or comes back in the same spot, is almost always water pushing out from behind the paint. On the outside of a house, Purdue says the water concentrates around joints and end grain, where siding and trim soak it up fastest. Inside, it comes from plumbing leaks and shower spray. Purdue also points to the water a household adds to the air every day: an average family of four, it says, adds about 3 gallons of water per day. Sherwin-Williams lists moisture migrating through the wall, damp basements, and oil or alkyd paint applied over a damp surface. Purdue says thin new oil coats are the most likely to blister, while old, thick coats tend to crack or peel instead.

Repainting does not fix moisture blisters. Purdue is blunt that the only cure is to get rid of the moisture. Sherwin-Williams’ list of fixes is about the building, not the paint: repair the leak, caulk joints, and add vents, exhaust fans or siding wedges so the wall can dry. Benjamin Moore’s blistering page says the same: when the blisters reach the substrate, remove the moisture source before repainting. If the wall is in a bathroom, the fan and the timing of showers matter as much as the paint. Our [bathroom paint and mildew guide](https://colorswatchlab.com/guides/bathroom-paint-and-mildew/) covers that.

## Fresh latex that met dew, fog or rain

There is one kind of bubble you can sometimes leave alone. Sherwin-Williams lists latex paint exposed to dew, high humidity or rain shortly after it dried as a cause of blistering, especially in kitchens and bathrooms. Benjamin Moore’s temperature guide says bubbles caused by rain may go away on their own, so leave them alone. If they are still there after a day or two, scrape, sand, clean and repaint. Sherwin-Williams’ repair article is less hopeful: it says paint bubbles won’t disappear with time and have to be repaired. Treat the wait as a short test, not a cure. To prevent it outdoors, Benjamin Moore says the surface should be more than 5°F above the dew point while you paint and while the paint dries.

## Bubbles in the second coat, or over old paint

If the first coat went on fine and the second coat bubbled, look at timing and compatibility. Sherwin-Williams’ repair article says to confirm the first coat is dry and that, generally, you should wait at least four hours between coats. The label on your can may ask for longer. Our [dry time versus cure time guide](https://colorswatchlab.com/guides/paint-dry-time-vs-cure-time/) explains why a coat can feel dry and still not be ready. Benjamin Moore lists oil or alkyd paint over latex, a damp, dirty or hot surface, and poor preparation as causes. If you are not sure what the old paint is, test it before you go over it. The alcohol test is in [painting over oil-based paint](https://colorswatchlab.com/guides/painting-over-oil-based-paint/). Indoors, Benjamin Moore also says to prime new joint compound with a latex primer and to seal stains with a primer-sealer, because unprimed patches and stains are where blisters tend to start.

## The repair that lasts

- **Find the cause.** Slice a blister and check the depth. For moisture, find and fix the leak, the drip edge, the missing caulk or the bathroom fan before you touch the paint.

- **Let it dry.** Purdue suggests a few days for heat blisters. A wall that was wet needs to dry out completely.

- **Scrape and sand.** Remove every blister and any paint that has loosened around it, then sand the edges so they feather into the sound paint. Sherwin-Williams also says to sand glossy surrounding paint dull.

- **Clean and prime.** Wash off dust and grime. Prime bare wood, drywall or any stained spot. Benjamin Moore’s repair for blisters that do not reach the substrate is to scrape, sand, prime, then topcoat with a quality acrylic latex.

- **Repaint under the right conditions.** Out of direct sun, within the temperature range on the can, and with the recoat time respected.

If the paint is coming off in sheets or flakes rather than blisters, that is a different failure. See [why paint peels](https://colorswatchlab.com/guides/why-is-paint-peeling/). If your house was built before 1978, the old paint may contain lead, so read [lead-safe painting](https://colorswatchlab.com/guides/lead-safe-painting/) before you scrape or sand. Scrapers, sanding supplies and primers are in our [wall repair and surface prep supplies](https://colorswatchlab.com/gear/wall-repair-and-surface-prep-supplies/) guide.


## FAQ

### Will paint bubbles go away on their own?

Usually not. Sherwin-Williams says paint bubbles won’t disappear with time. The exception is fresh latex that got wet before it dried: Benjamin Moore says rain bubbles may go down by themselves, so wait a day or two before you repair them.

### Should I pop paint bubbles?

Popping a blister does not reattach the paint. Wait until it is dry, then scrape it off, sand the edges smooth, fix the cause, prime any bare spot and repaint the patch.

### Why is my paint bubbling on the second coat?

Usually because the first coat was not ready. Sherwin-Williams says that, generally, you should wait at least four hours between coats; follow the label if it asks for longer. Heat, a thick coat, or oil-based paint over latex can also cause it.

### How do I know if blisters are caused by moisture?

Cut one open. Purdue Extension says moisture blisters usually go through all coats to bare wood and contain water when they form. Heat blisters appear only in the last coat.

### Can I paint over bubbled paint?

Not directly. New paint over a blister seals in the problem, and the blister can push up the new coat too. Remove the blisters, sand, prime bare areas, then repaint.

## Sources

- [Paint Failure Problems and Their Cure, NCR-133 (Purdue University Cooperative Extension)](https://www.extension.purdue.edu/extmedia/ncr/NCR-133.html)
- [Blistering, problem solver (Sherwin-Williams)](https://www.sherwin-williams.com/homeowners/how-to/problem-solver/peeling-cracking/blistering)
- [Paint Bubbling and Blistering (Benjamin Moore)](https://www.benjaminmoore.com/en-us/contractors/job-solutions/troubleshooting/paint-blistering)
- [How to Fix Paint Blistering (Sherwin-Williams)](https://www.sherwin-williams.com/en-us/project-center/maintenance-repair/how-to-fix-paint-blistering)
- [How to Fix Bubbling, Pinholes and Cratering Paint (Sherwin-Williams)](https://www.sherwin-williams.com/en-us/project-center/maintenance-repair/how-to-fix-bubbling-pinholes-cratering-paint)
- [Foaming / Cratering, paint problem solver (Behr Pro)](https://www.behr.com/pro/resources/paint-problem-solver/paint-problem-solver-detail/foaming-cratering)
- [Temperature Guide for Exterior Painting (Benjamin Moore)](https://www.benjaminmoore.com/en-us/interior-exterior-paints-stains/how-to-advice/exteriors/temperature)