Why Paint Blisters, and What to Do About It


By John Shearer Painting Contractor  206-431-3606

June 15, 2003

After a big paint job, blisters and bubbles are the last things you want to see; but it happens all the time. Latex and acrylic paint are especially prone to blistering and bubbling, but these problems can occur with any kind of fresh paint finish. They can happen on interior or exterior surfaces, and they’re more likely to arise when preventive measures haven’t been taken. You might ask several experienced painters and you might get as many answers why paint bubbles and blisters; likewise from paint dealers and manufacturer reps. I have been a painting contractor since 1990 and I will will share my experience with old homes.

Where Do Blisters and Bubbles Come From?

Blistering is what happens when the top coat of paint parts ways with the coats beneath it. Sometimes the top coat can take away multiple coats of paint with it.. almost like a piant stripper!! Unfortunately, this phenomenon is nearly impossible to predict. It may appear suddenly or occur gradually, over the course of many months. Blistering is likely on a moist surface that wasn’t properly dried before it was painted. Applying paint to areas of a house that tend to be humid, like basements, requires particular care.

Painting an exterior just before it rains can be every bit as harmful as putting paint on a wall that’s already wet. If a storm is expected, refrain from painting for a total of eight hours: the four hours preceding its arrival, and the four that follow. A humid day can lead to water-filled blisters, which must later be scraped and touched up. This is not a hard firm rule… painting must go on and reputable painting contractors must still proceed with the project; in our experience it is only once in two years that a paint coat is dmaaged from rain heavy enough in the four hour “after period” to effect a

If a wall is unclean, do not prime or paint it. If a surface is covered in oil-based paint, it’s best to use oil, not latex, when repainting it. Mixing types of primer and paint on the same wall can lead to problems, especially on exteriors. Heat causes surfaces to expand, and latex and oil paints behave differently in that situation. Ultimately, the latex may take the oil clean off the wall.

house paint bubbles

Consider that chemistry can also play a part in the formation of bubbles. In hot weather, the upper stratum of paint may dry quickly, which traps and subsequently vaporizes the paint’s solvents. The solvents, in turn, increase in volume, which creates — you guessed it — bubbles. To avoid this fate, paint in the shade whenever possible, and don’t paint at all when the temperature outside is 85 degrees Fahrenheit or above.

If all else fails, a conditioner can help keep freshly applied paint from dying too quickly. Water-based paints are compatible with Flotrol, while Penitrol works with oil paints; these are commercially available paint “extenders” designed to help improve paint flow for brush and roller work. Linseed oil can be used to extend drytime for solvent based finishes. Dont go crazy with extenders the performance of your paint may suffer. Thinning paint with water or mineral spirits may seem like a good idea, but it only makes things worse… often speeding up the drytime.

Preparation might be the most important part of exterior painting. A surface that’s experiencing blistering or bubbling is certainly not beyond repair; scraping it and applying a new coat of paint should do the trick. That said, do not take a Band-Aid approach to persistent problems. If blistering and bubbling recur, they may not stop until you figure out what’s creating the trouble and take appropriate action.


What are Paint Blisters and How to Avoid Them..On interior walls

There is more to painting a house, inside or out, than choosing paint, buying paint brushes and slapping paint onto the surface of walls. Before even beginning to paint, you need to know what is already on the walls and how to prepare them for the paint. For example, if the walls are papered, especially if paper has been pasted over paper, painting the walls may well rip that paper right off the walls in chunks. Paint blisters are another real possibility if you do not correctly assess and prepare the walls before painting. There are any number of things to avoid when painting and blisters are one item to be avoided.

What are Paint Blisters
Blisters are caused when the newly applied paint detaches from the surface beneath for one reason or another. The blisters look rather like pox on a face and are unsightly bumps on the smooth paint surface. The blisters can be caused by heat, moisture, incompatibility and more. Here are ways you can avoid paint blisters.Clean it Up
Though many do not realize it, dust and grime attaches even to the flat of a wall surface. Of course, you need to check for spider webs in corners, but it is also important to clean the entire surface you plan to paint. Dirt, stains and grime keep the paint from clinging properly to the wall. Not only is it important to clean the walls before painting, it is also important to consider what you are using to clean. You want to make sure not to leave fluids, oil or any other contaminants that might cause blistering behind on the surface before you start painting .Make Sure the Wall is Dry
While you might be impatient to get that new color on the walls, do not rush into painting before making sure the wall is totally and completely dry. After cleaning the walls, give them time to dry. This will depend upon season, weather and humidity, Moisture can cause that newly painted wall to blister, leaving you frustrated.This also applies to primer. Many times, a wall needs a coat of primer before the actual paint goes on. Primer prepares the wall surface and helps paint to adhere better. However, primer needs time to cure or dry before paint is applied. Evaporation a paint drying process. If paint is put on before the primer is fully dry, evaporation trapped between layers causes paint blistering.Not a Good Mix
Even if you do not start painting until the wall is clean and dry and the primer is fully cured, blisters may happen. Paint and primer do not always work well together. This possibility decreases when both primer and the paint used are purchased from the same manufacturer. If this problem persists and there seems to be no other reason for the blistering, call or email the manufacturer. With the use of the Material Safety Data Sheet (MSDS), the manufacturer should be able to let you know if you should use the paint with a particular primer.Heat is Not Always Your Friend
Summer seems like the perfect time to repair,replace, paint and do other maintenance household chores. However, too much heat while painting can be a problem. Paint needs heat to dry thoroughly. However, if the temperatures rise too high or too quickly, paint will not dry evenly and blistering may happen. Always check the weather and the manufacturer’s recommendations before dipping that brush into the paint can.Finally, Check the Paint
You’ve done everything you can to ready the walls for the next step–paint. You have cleaned and primed the walls. You’ve let them dry completely and you have made sure the primer and paint work together. The weather when you paint is neither too hot, cold or humid. Still, the paint blisters. The problem could be the paint used.Sometimes paint is mixed incorrectly. To prevent blistering from the paint itself, follow the manufacturer’s directions for mixing the paint. Test on a surface other than the wall. If it blisters, the problem might be the mix ratio. Make sure the paint is right and ready to go before applying it to your walls.

  • Redhill Painting

    Thanks for the info, John. We’ve come up against this particular problem quite a bit in SF. Especially so when we’re painting darker, saturated tones and always in areas that get a lot of direct sunlight. Even when we pop the bubbles and prime with Cover Stain they tend to come back in the same localized area. In a large percentage of cases when we pop the bubbles we notice the bubbles open up right to the bare wood. This has prompted some painters to theorize that the linseed oil had dried out in the original layers that sit on the wood and when the fresh top coat dries it pulls the old layer away from the substrate.

    • Lou

      I have exactly these same conditions. We are an hour north of Seattle, but summers are usually dry and warm, highs in the 70’s. 5 years ago I painted our 50 year old house (with nice VG cedar siding, in great shape) a dark hunter green. The house was well prepped, I waited a few dry days to paint after pressure washing, and always painted in the shade. I did everything right. Within a day, blisters were popping up everywhere, mostly in areas with only partial direct sun, facing east and south between the shade trees in the yard. The adjoining garage also did it, so I’ve ruled out a vapor barrier, interior moisture problem. The perplexing thing: The bubbles are dry, and go through 5 different layers of paint all the way down to the original primer. The paint doesn’t come off as chips, you can peel it off once you pop the bubble. Yesterday I meticulously scraped and sanded the entire house to prep for new paint, today there are 30 new bubble, where direct sun hasn’t hit.. It’s going up to 85 today, so it’s warmer than usual. I’m scared to paint!!! The house is for sale, it’s beautiful weather, I need to get it painted. I want to go with a rich barn red, but i’m shying away from a dark color again.
      Any ideas, anyone? After 50 years, why now?

      • michael

        I have the same problem. What did you do to correct the problem?

      • guest

        It is correct Red Hill old layer past its expansion/contraction cycle. Somewhere around 50 years under average conditions. Modern coatings heavy and create a lot of surface tension.
        Use some wood conditioner, light bodied primer preferably high elongation type like United bonding primer . Best of all is to completely remove paint from compromised areas.
        Homeowner tool would be chemical strip or infrared heater. Area needs to be sanded and let dry at least 4-5 days at 60-70 F. Most important do not overload old film and do NOT USE roational sander. Painting is easy, right .. NOT
        Linsseed oil promotes growth of mold and mildew.

    • johnshearer

      Philip, Thanks for the comments about the oil in the wood drying out on the top layers. We have a long practice on trouble substrates where we apply a thinned layer of linseed oil mixed with Benite..then prime and paint.


  • BCascioli

    I am currently painting my kitchen. Cabinets, walls, and trim. I bought Valspar bonding primer for my cabinets and trim to avoid sanding. The primer went on beautifully and so did the paint. Dried well and looked great until the window trim above my kitchen sink was splashed with water more than two weeks aftrr the paint was applied. The area that got wet bubbled up within an hour and the paint wiped right off. Leaving the primer behind. I light scratched at the area with my finger nail and the primer came up as well. Someone HELP! Can I paint over everything with oil based primer and paint or do I sand everything off and start over? What would cause it to only peel up if it gets wet?

  • lily

    small parts of interior wall painted with emulsion has bubbled. could this be due to glue from putting on coving, if so how do i rectify this problem

    • johnshearer

      Most likely moisture trapped behind emulsion.

  • Sherri

    Purchased my 30 year old home as a bank foreclosure….it was originally stained wood ship lap siding, (not sure if it’s cedar or not) and apparently the previous owner painted over it without sealing…..it looks like the first picture in your article……ALL the paint is peeling off, some in huge long strips, other is just big bubbles….My regular painter wont’ even bid it for paint as he says it is too labor intensive to remove the paint and get to the wood….Is this something that can realistically be “fixed” or should I just look at some type of vinyl siding or ????? Thanks in advance……

  • nat8908

    I just moved in to a property and it needs painting. I have just noticed that the room I am due to wash and paint has bubbles. I am tempted to pop them. One that has already popped and flaked off like really thin plastic/ acrylic? The paint is direct on to plaster- so I’m guessing the plaster wasn’t dry.
    How do I go about painting now?

  • jan

    I recently bought an older house to rent. The paint was in good condition when I rented it. After 3 weeks of the renter being there they said the paint was peeling and blistering. It seems to have a gloss paint under a flat paint. Which is a painters nightmare. Anyone know how to get the flat off to use the correct paint coat on the gloss?

    • Philip Storey

      Personally I would use a power sander to remove the flat paint. prime and finish.

  • Martin Quinlivan

    hi i sanded my front door basically back to d timber, cleaned it and usesd a primer/undercoat sanded and cleaned gain and put a high gloss on it,was fine for about a week but d inside of d door is not exactly blistering but creasining(like paper) if tat makes sense, in several spots and still feels to sticky or tacky to sand for another coat. i live in ireland where its all sorts of weather.any advice?

  • Belinda Choi

    You have to sand off all the loose primer, The best primer to apply is STIX sold by Benjamin Moore.
    It is latex but is so stong at bonding it will stick to tiles.
    It also works better with (latex paint ) used in the final coat because it is latex.
    Stix is nice to work with ,easy to clean and better than the alkaid latex mix primers sold by sherman williams. The alkaid latex mix primer can cause paint bubbles when you put latex on top. Always use the same mix of paints ie oil & oil, latex and latex…mixing them sometimes can cause this reaction.
    Also use paints from the same manufacturer as paints from different companies occationally are not compatable

  • emma smith

    ok guys so my problem is i have one full conservatory wall when we moved in we chose to paint the wall and the old paint started to peel we then painted the whole wall and peeled the old one off and repainted the wall this went well for a few days then slowly over time the right hand side of the wall started to bubble and flake off weve struggled to fix this problem weve repaint used primer and it still did it we are currently useing a exterior paint in hope that will work but a few bit bubbled up straight away so we went over them bits again pressing harder it seems to help but does anyone have a better solution to this problem please

  • Bryan

    It appears under my wall blisters that the gypsum paper cover is breaking down. Is there any insects that eat them?

  • PaintBlisters

    We just had our 100-year old Seattle house exterior painted. The contractor (who was a nice guy with >30years of painting experience) used high quality SW paint and appeared to do all the prep work correctly. He did end up painting some of the house in the hot sun, but not all sides. Now that he’s done, we have noticed a progressively growing number of paint bubbles/blisters. These are mainly on the west side of the house, but all sides now have at least a few. The paint that is bubbling is pulling all the underlying layers of paint right off the grooved cedar shingles. The house was last painted 15 years ago without any issue. QUESTIONS: Is this a bad paint job by the contractor, or are we just having bad luck? How long before the blistering stops? Thanks for any advice.

    • Fax Bedamt

      I’m in Seattle, and am suffering same exterior blistering, by the
      hundreds. Both the experts at Daly’s and SW have suggested that the old,
      lead-based primer on my exterior siding has oxidized and let go.This is
      evidenced by paint dust under the blisters, which are pulling up ~60
      years of paint (six or seven layers). I suspect that the higher humidity
      in the PNW, combined with old, leaky construction and sometimes extreme
      summer temperature swings comes into play as well.

      I have done
      my best to eliminate air intrusion into my exterior walls by caulking
      baseboards and electrical penetrations, insulating, etc., but there is
      no way I can completely seal the concrete foundation and the basement
      walls and floor.

      My problem is, is there a way to feather the
      edges of the scraped blisters, so they don’t stand out when I repaint,
      without gouging into the siding? Is there a filler that will accommodate
      expansion and contraction?

  • LF

    Thanks. I mudded some imperfections (3 tiny blisters) and sanded and painted, again, apparently too early. I even cut the blisters with a razor, and they do come back.

    The wall previously (10+ years ago) had lots of skin coating to revive wall paper removal. I probably didn’t wipe that sanding down well, figuring it would just get mixed in the paint.

    Thanks for the information. Once again, it proved one can’t take too much of short cuts.