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What are Paint Blisters/Bubbles, 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.

Key Summary

TopicKey Points
Causes of Blisters/Bubbles– Caused by the top coat separating from underlying layers.
– Likely on improperly dried surfaces or in humid conditions.
– Can be exacerbated by painting before rain or in high humidity.
Preventive Measures– Ensure surface is clean and properly prepared before painting.
– Use appropriate type of paint for the surface (e.g., oil-based over oil-based).
– Avoid painting in extreme temperatures or just before/after rain.
– Consider using paint conditioners like Flotrol or Penitrol to manage drying times.
Fixing Blisters/Bubbles– Clean and dry walls thoroughly before painting.
– Allow primer to fully cure before applying paint.
– Ensure compatibility between primer and paint, preferably from the same manufacturer.
– Avoid painting in high heat to prevent uneven drying and blistering.
– Check the paint’s mix ratio and quality before application.
Professional Advice– Choose reputable contractors.
– Follow manufacturer’s instructions for paint mixing and application.
– Monitor weather conditions closely before starting exterior projects.

Where Do Blisters and Bubbles Come From?

Blisters or bubbles in paint occur when the top coat separates from the underlying layers. This can happen suddenly or gradually over many months and is difficult to predict. It’s particularly likely on surfaces that haven’t dried properly, especially in humid areas like basements.

Painting just before it rains can also cause issues. To avoid problems, it’s best not to paint exteriors four hours before and after a rainstorm is expected. High humidity can cause the paint to form water-filled blisters that will need to be fixed later.

When choosing a paint contractor, ensure they are reputable, especially since rain shortly after painting can sometimes damage the paint job. Always clean and prepare surfaces before painting, and use the appropriate type of paint for the surface. For example, if a surface is already painted with oil-based paint, use oil-based paint again rather than latex. Mixing different types of paints can cause problems due to how they react to heat and expand differently.

Temperature also affects painting. In hot weather, the top layer of paint can dry too quickly, trapping and vaporizing the paint’s solvents, which then expand and form bubbles. Avoid painting when the temperature is above 29 degrees Celsius.

If paint is drying too quickly, using a paint conditioner can help. Water-based paints work well with products like Flotrol, while oil-based paints can be used with Penitrol. However, be cautious with these extenders as they can affect paint performance if used excessively.

Proper preparation is crucial for successful exterior painting. If you encounter blistering or bubbling, scrape off the damaged paint and apply a new coat. If the problem persists, it may be necessary to investigate further to find and resolve the underlying issues causing the paint to fail.

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.

How to Fix Paint Blisters/Bubbles?

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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