Why Paint Blisters, and What to Do About It
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.
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.
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.