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Bubbles appearing while you’re painting is fairly common; however, the problem needs attending to in order not to ruin your hard work. So why have bubbles appeared?
The 5 most common causes of bubbles and blisters in your paintwork are when the surface is damp or dirty, there’s a chemical reaction from old paint residue, you’ve used the wrong paint or primer, and extremes in temperatures that prevent proper drying. Bubbles are also common after prolonged rainfall.
As well as looking at the causes of bubbling, this article is going to show you:
- Expanding bubbles and other damaging effects of rainwater
- Why bubbling needs your immediate attention
- How to fix the problem and ways to prevent it in the future
Why Is My Exterior Paint Bubbling?
Bubbles appearing on the surface of your paint are also known as blistering. Blistering is caused by the paint failing to stick, and it separates from the surface you applied it to. The reason for blistering can be down to several reasons, such as:
1. Damp Surface
A common place for an exterior wall to blister is down near the ground. Hydrostatic pressure is when a wall draws up water from the ground, which in turn will cause your paint to bubble off.
You may have high groundwater in your area if you are experiencing heavy rainfall and the ground is saturated. Look on the inside of the wall to see if it is damp in your home. It may also be the case that you have a leak that needs fixing before you move on to the paint.
2. Dirty Surface
Caked-on mud, grime, and mold function as a barrier between your paint and the wall. The fumes from cars and factories will also cling to the outside of your home. This layer of pollution contains oils and other chemicals that will react with your paint, causing it to blister. Your paint will not be able to get through this barrier and adhere to the material beneath.
3. Chemical Reaction
Fresh paint is sensitive to chemical residues from things like old paint or oils and the extremes of weather. Direct heat from the sun or even indirect reflections off other buildings can cause the paint to blister.
A hot surface will cook the paint as you apply it and cause pockets of fumes to expand beneath the skin of the paint. In extreme conditions, heat can cause huge blisters to form, especially if the surface is also wet.
4. Wrong Paint
Always check that the paint you are using is suited to the primer and the surface you are applying it to. Oil-based paints are tough and sticky and can last a long time on surfaces that see a lot of weather.
Oil-based based paints repel many types of liquids, including water, and will not sink into the surface you want to apply them to. It is better to use water-based latex paints that will soak into masonry, which will also stretch over and seal the wall.
5. Poor Drying Conditions
Bad drying conditions include extreme heat but also humid, freezing, and wet weather. Often the simple cause of blistering paint is from trying to apply it after heavy rain. Freezing weather conditions may slow your paint’s drying time and cause condensation to form on the paint. Any stagnant water on or behind the surface of the paint is going to cause blistering.
Exterior Paint Bubbling After Rain
A wet surface will give you poor paint adhesion. A frequent problem when painting outside is rain, and it can fall when you are halfway through the process. For paint to adhere to a material, the surface needs to be dry. If the surface is already saturated with water, it cannot draw the paint in.
Oil-based paints are hydrophobic, so if there is any water on the surface, the paint will want to rest on it. Some water-based latex paints are also hydrophobic, which is why it is better to paint on a dry surface with any type of paint. Shrinkage will begin the moment you lay the paint on the surface. Most of the stretching finishes after 24 hours, though it can continue for up to a week.
Rain may prolong the drying period, especially if you get continuous rainfall after painting. Paint is very sensitive to temperature and dries best if the whole surface gets to dry at the same rate. As rainwater lands on your fresh paint, it will cause some areas to dry and shrink at odd speeds.
Rainwater may also work its way in between the paint and the surface, pulling it out. The water will then be trapped between the surface and the paint. As the water inside expands in the sun, it will bubble.
These expanding bubbles can even end up pulling more paint away from the wall. The larger the bubble, the more damage it will do, and the harder it is to fix. Smaller bubbles may disappear without you having to do anything else.
Will Paint Bubbles Go Away on Their Own?
Water in the paint bubbles will go, but you need to consider the amount of damage they will cause before they shrink. Either way, leaving the water sitting on the surface of your home is going to cause some form of damage. Bubbles are a sign the water is now sitting in a space between the wall of your home and the paint. Leaving large bubbles alone can cause more problems than just peeling paint.
If the bubbles are small, they should shrink and leave you with a smooth surface. Large paint bubbles often burst open, creating flaps of paint that you will need to scrape off and recoat. If the water in the bubbles does not evaporate, it will form mold and mildew beneath the paint.
Stagnant water on brick may cause the masonry to fall apart. If the bubbles are on wood, the moisture may start attacking it and begin rotting it. The water in a paint bubble may also find its way into the crack that you attempted to paint over. Cracks are a good hiding place for water when disguised with a layer of paint, making them harder to find.
How to Prevent Paint from Bubbling
Remove any crumbling brick, wood, or concrete that will prevent the paint from making solid contact with your wall. Old chemicals and dirt will stop the paint from sticking to your wall, increasing the chances that it will blister as it dries.
A good sealant will hold together fragile masonry and add an extra layer of protection from water trying to soak into your home. The primer will provide a tacky surface to help the paint stick better and help prevent bubbling.
Check the weather forecast before you commit a whole day to painting your wall. If you are expecting days of high humidity, heavy rain, or snow, leave it for another time. The ideal conditions are sunny with a couple of days of dry conditions.
If the conditions change, you might still be able to rescue your paint by setting up some floor fans. The movement of air helps to remove moisture so that the paint can dry faster and evenly.
How to Fix Bubbling and Blistering Paint
It can be an upsetting prospect when you realize that the paint you spent a lot of time applying is bubbling so bad that you must take it off. Blistering paint looks terrible, but it can also cause damage to the interior of your home, so it needs to go.
Start by looking for the root cause of why the paint is blistering. Was it because you painted during humid weather? Are there a lot of cracks in the wall, and did the wall have a lot of old paint on it?
Use a scraper to remove the biggest blisters. If you are dealing with small bubbles, you may get away with sanding them off and leaving the rest of the paint on the wall. Scrape off any big chips and flakes, and scoop out crumbling masonry.
Before you break out your brush and paint, make sure that you are starting with a clean surface. Use soap, water, and a sponge to wash down the wall, or use a pressure washer.
You can speed up the drying of your wall by padding down the surface with clean rags. Or you can set up a series of floor fans and have them blow onto the wall until it is dry. Let the wall dry before moving on.
- Caution: Be careful when removing old paints since they can release lead fumes. Wear goggles and a respirator when sanding or scraping off old paint and filler.
If you have large cracks in the brick, concrete, or woodwork, it is worth spending some time applying a thicker sealant with a scraper. Let the sealant harden, and then sand down any lumps left over. A flat surface will not hold on to water, and it is easier to work with when it comes around to painting.
Once you have filled the big holes, paint on a primer and sealant. It is better to let the primer dry for the full recommended period stated by the manufacturer to give your paint the best surface to adhere to.
When mixing the paint with a paint mixing attachment on a drill, set it to slow speed to avoid making too many bubbles. Use a roller or a brush to paint your repaired wall. A roller will give you a consistent coat, but a brush pulls less on old paint. So, if you are painting a small area, but your wall is still crumbling, it may be better to use a brush.