Paint Problems, Episode I: The Blistering Menace
Updated: Aug 29, 2019
At some point or another you are going to run into paint problems, it’s inevitable. But don’t panic we know the issues and we can offer up solutions. So, for the next little while L.A. Design Centre will be blogging about… you guessed it, Paint Problems!
Let’s jump right in shall we!
Episode I- The Blistering Menace
First off, what is it?
Blistering is the formation of bubbles in your dry paint film. They can vary in size and quantity and can occur in small areas or across your whole project. These bubbles are a loss of adhesion between the new paint and the underlying surface. It can be between layers of paint or between the paint and underlying substrate. Blistering often leads to further issues like flaking or peeling.
But why? What went wrong?
There are many reasons for this loss of adhesion. I find the most common one is improper surface preparation. When is comes to achieving a beautiful, lasting paint job, surface prep is key. If you apply your product to a dirty surface it won’t stick, the contaminant acts like a barrier preventing your lovely new paint from bonding to the surface. Make sure you wash with a good degreaser, like TSP, before painting your project. And remove any loose or flaking paint from a previous paint job. For further instructions on proper surface preparation see our previous blog post, Be Prepared: A Surface Story.
The next thing you need to consider is if you should have used a primer. Not all surfaces will need primer. For example, if you are using a high-quality paint on a previously painted surface then usually no primer is required. But bare drywall or new joint compound is a whole other story. Porous surfaces need a good quality primer that is specifically designed for them.
But maybe you did some serious surface prep and primed where and when you needed to, and it still happened. What could it be now??
Well moisture on or in the substrate may be the culprit. Painting over a wet or damp surface, or unseen moisture within the surface can lead to blistering as well. Causes of this moisture might be water droplets that got splashed onto the surface, dew from a cool morning, high humidity, or even a plumbing leak inside the wall. Whatever the case maybe, the moisture and/or the source of the moisture needs to be eliminated before painting otherwise it gets trapped beneath the paint film and causes these pesky blemishes. I recommend doing this before your surface prep.
Now you’re thinking, ‘okay Jenna, my surface was clean and dry, and I primed it, but it still blistered. What did I miss? Or is it just crappy paint?”
Well, it could be your paint. Lower quality, bargain brand paint has inferior adhesion capabilities, but let’s consider that the final answer after we’ve addressed other potential causes first. Like the temperature for instance. Was the surface temperature or the surrounding air temperature too hot? All that hot air (and no I’m not talking about your in-laws, your spouse, or that know-it-all neighbour) causes the surface of your new paint to dry unevenly and too quickly. This traps the solvent underneath and leads to, you guessed it, ugly bubbles in your brand-new paint job. Make sure you’re not painting a hot surface, in direct sunlight or if the air temperature is too hot. If it’s too hot for you to work in comfortably it’s likely too hot for your paint.
If you did your prep, primed, eliminated any moisture and the temperature was reasonable then it could be that you applied an oil-based product over a latex. Or maybe you applied your paint with the incorrect roller cover. If the roller isn’t suited for the texture of the surface or the product you are using it could result in uneven coverage. In exterior cases a dark color may be the culprit. Very dark colors absorb heat and cause greater expansion and contraction of the substrate. This puts excessive stress on the new paint and can cause it to fail.
And if nothing else, maybe you did choose a lower quality paint.
Now that we’ve covered what blistering is and why it happens let’s talk about how to fix the problem.
First, make sure you have eliminated any possible sources of moisture. This might be as simple as waiting for things to dry out or you may have to do repairs, redo some caulking or install vents or fans. Then you need to do adequate surface prep. Start by removing the blisters and any other loose paint by scraping. Clean the surface with a good degreaser. If using the powdered form of TSP make sure you rinse as it leaves behind a phosphate residue. Next sand to get rid of the ridge left by the blisters or any other loose paint. I like to give the whole surface a light sand after I’ve smoothed out the problem areas, so the new paint has a more adequate surface to stick to. If you find you are having problems getting everything smooth you can use a little patching compound to fill in the low areas where the blisters were, just make sure you don’t forget to sand your patches before you put on the new paint. Prime if needed. Make sure you are using the correct primer for the job. Your local paint store should be able to recommend the correct primer, or you can contact me at L.A. Design Centre. Then apply your new paint using the correct roller. Again, your local paint store should be able to point you in the right direction.
Prevention is best. Let’s not get blistering in the first place.
1. Remove any moisture. This may mean doing repairs.
2. Adequate surface preparation. (Check out our blog post Be Prepared: A Surface Story)
3. Make sure the surface temperature and air temperature are not too hot.
4. Prime with an appropriate primer if needed.
5. Apply your paint evenly, not too thick, and with the correct application tools.
6. Do not put oil based over latex.
7. When it comes to exterior paint, dark colors can create problems.
To fix the problem take it one step at a time.
1. Eliminate any sources of moisture.
2. Scrape off the blisters and any other loose paint.
3. Adequate surface preparation. (Check out our blog post Be Prepared: A Surface Story)
4. Sand the ridges from the blisters smooth. Use patching compound if needed. Sand your patches.
5. Prime with an appropriate primer if needed.
6. Apply your paint evenly, not too thick, and with the correct application tools. Use a lighter color if possible.