From time to time we receive questions that involve problems professional painters are having on the job. Most often these questions are complex and result in interesting solutions. Occasionally, however, we address an issue that we take for granted as common knowledge but, in fact, is not readily known. I recently received an email from a new home-painting business based in Connecticut. The message read as follows:
“We recently were painting the inside of a 3 room bungalow and couldn’t get the primer to adhere to the walls. We made sure the primer was properly stirred and checked moisture levels but still had issues. Is it possible there was something left on the walls that was causing the primer to not behave correctly? Do we need to be looking for additional additives? ”
After answering her email (yes, you need to check to make sure the walls are clean before applying primer) it occurred to me that many painters, professionals even, don’t know all the reasons why they might run into paint adhesion problems. Furthermore, many of them might not realize that one of their primary materials – primer – was actually designed in part to combat these problems. This lack of knowledge can have practical implications that turn a job that was supposed to be profitable in to a major pain.
Most professional painters can tell you some good reason to use primer: it can cover stains and imperfections in the substrate, fill in small crevices and cracks, and help give the final paint coat a nice, smooth finish. What many of them don’t realize is that the chemistry of primer is fine tuned to offer a more significant use: it helps the paint stick to the surface the same way glue helps wallpaper stick to a wall.
As a result, using primer that doesn’t properly adhere to the substrate can be a waste of precious time and money for professional painters. As a refresher, the most common reasons for primer or paint to not adhere correctly to a substrate are:
- Dirty walls – Often cleaning with a non-oil based cleaner, even wiping with a wet cloth, can clean the wall enough for the paint to adhere.
- Unmixed paint or primer – Paint chemistry relies on the paint being properly mixed for it to behave as intended.
- Too much moisture or too cold – Paint and primer react differently in abnormal environmental conditions.
- Working the paint or primer too often – There is no need to continue running your roller or brush over the same area, which can result in the paint balling up or clumping.
Running into problems with paint that won’t stick to walls almost always can be traced back to primer that won’t stick to walls. It is important to understand that primer continues curing for days or even weeks after being applied to create a strong chemical bond in both directions – on to the substrate and on to the paint in the other. Primer is not intended to coat the surface as a paint replacement, but rather to offer a layer that works with both substrate and paint to form a cohesive bond between the two. Think of primer as an undershirt when wearing a gorgeous, but itchy sweater. The undershirt keeps your skin comfortable while allowing you to still wear a clothing item that might otherwise be uncomfortable.
The paint company in Connecticut was wise to wait and solve the problem of getting the primer to stick to the walls before applying paint to the wall as well. You would be wise to follow their lead and treat your primer coat as a vital part of the paint adhesion process. Yes, adding a coat of primer adds time to the job. But great results – including uniform paint adhesion – begin with your coat of primer. In a future post, we’ll learn more about testing paint adhesion. Until then, click here to learn more about getting ready for your next paint job!