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Why Paint Blisters, and What to Do About It

After a big prep intensive paint job, blisters and bubbles are the last things you want to see. Still, Paint peeling and blisters happen all the time, EVEN to professional painters. Latex and acrylic paint are prone to blistering and bubbling, but these problems can occur with any 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 get as many answers as to why paint bubbles and blisters; likewise, from paint dealers and manufacturer reps. I have been an exterior painting contractor since 1990, and I will share my experience with old homes.


Where Do Blisters and Bubbles Come From?

Blistering happens when the top coat of paint parts ways with the coats beneath it. Sometimes the topcoat can take away multiple coats of paint, almost like a paint stripper!! Unfortunately, this phenomenon is nearly impossible to predict, and it may appear suddenly or occur gradually over many months. Blistering is likely on a moist surface that does not dry properly before being 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 exterior painting for eight hours: the four hours preceding its arrival and the four following. A humid day can lead to water-filled blisters, which must later be scraped and touched up. It is not a complex, firm rule painting.

Choose a reputable exterior painting contractor to proceed with the project. In our experience, it is only once in two years that a paint coat is damaged from rain heavy enough in the four hours “after a period” to effect. 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 primer and colour types 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.


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. Don’t paint when the temperature outside is 85 degrees Fahrenheit or above.

A conditioner can help keep freshly applied paint from drying too quickly if all else fails. 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 the dry time for solvent-based finishes. Don’t 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 worsens, often speeding up the dry time.

Preparation might be the essential 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 an exterior painting a house, inside or out than choosing paint, buying paint brushes and slapping paint onto the surface of walls. Before you start painting, you need to know what is already on the walls and how to prepare them for the exterior painting. For example, if the walls are papered, especially if the paper has been pasted overwriting, painting the walls may rip that paper in chunks. Paint blisters are another possibility if you do not correctly assess and prepare the walls before doing an exterior painting. There are many 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 like a 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 attach even to the flat of a wall surface. Of course, you need to check for spider webs in corners, but it is also essential to clean the entire surface you plan to paint. Dirt, stains and grime keep the paint from clinging correctly to the wall. It is necessary to clean the walls before making an exterior painting. It is also vital 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 exterior painting. 


Make Sure the Wall is Dry – While you might be impatient to get that new colour on the walls, do not rush into painting before making sure the wall is totally and arid. After cleaning the walls, give them time to dry. It will depend upon the season, weather and humidity. Moisture can cause that newly painted wall to blister, leaving you frustrated. It applies to primer.

A wall often needs a coat of primer before the actual paint goes on. Primer prepares the wall surface and helps the paint adhere better. However, primer needs time to cure or dry before paint is applied—evaporation is a paint drying process. If the paint is put on before the primer is fully dry, evaporation trapped between layers causes paints to blister.

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. The paint needs heat to dry thoroughly. However, if the temperatures rise too high or too quickly, the 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, 

  1. Follow the manufacturer’s directions for mixing the paint.
  2.  Test on a surface other than the wall. If it blisters, the problem might be the mix ratio.
  3.  Ensure the paint is correct and ready to go before applying it to your walls.

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