Why Paint Blisters, and What to Do About It

why-paint-blisters

By John Shearer House Painting Contractor
Commercial Painting Contractor

After a big paint job, blisters and bubbles are the last things you want to see. Latex and acrylic paint are especially prone to blistering and bubbling, but these problems can occur with any kind of 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.

Where Do Blisters and Bubbles Come From?

Blistering is what happens when the top coat of paint parts ways with the coats beneath it. 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.

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

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 condition can help keep freshly applied paint from dying too quickly. Water-based paints are compatible with Flotrol, while Penitrol works with oil paints. Thinning paint with water or mineral spirits may seem like a good idea, but it only makes things worse.

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.

house-paint-blisters

Read more about peeling paint

Read Benjamin Moore Paints information on bubbling paint

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.

Here is a paint bubble failure from a house in Seattle April 2013

  • 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.

      http://www.shearerpainting.com/benitewoodconditioner.php

  • 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?