Working as a paint advisor, I’m often asked: is it really necessary to apply a primer? Before you get an answer, you first need to understand its role. The primer, also called a “primer,” allows the finish coats to adhere properly to the surface. It allows you to cover in fewer coats (and therefore save money!), avoid problems caused by contaminants, and prevent incompatibilities between products.
We’ll explain in detail when you need to use a primer, why, and which product to choose!
01
2-in-1 Paint versus Primer + Finish: What's the Difference?
Many paints are marketed as “two-in-one” products, intended to suggest that these products fulfill the function of a primer. This is not entirely accurate.
While it’s true that these are generally paints with very good coverage, they do not replace the sealing effect of a primer. These paints will, for example, better hide a dark color, but will not solve the problem of a stained surface or soiled surface, will not seal porous surfaces (such as new drywall), and will not allow the transition from an oil-based product to a water-based finish.
02
Which Primer to Use for Transitioning from Oil-Based Paint to Water-Based Paint?
In older homes where the walls haven’t been painted in decades, it sometimes happens that the old paint is oil-based.
If this is the case in your home, it’s non-negotiable that you apply a primer before applying water-based paint. Why? Because water-based paint cannot adhere durably to an oil-based product.
You’ll need an oil-based primer or an ultra-adhesive primer like Stix to make the transition without adhesion problems.
How to Recognize a Poor Transition?
If you apply water-based paint directly over old oil-based paint, problems will generally appear quickly. You might observe:
- Blisters or bubbles forming in the finish.
- Premature cracking of the paint.
- The new coat peels and detaches.
If you observe any of these phenomena, remove all paint that is peeling from the wall or flaking by scraping or sanding. Then, apply an oil-based primer like Coverstain to ensure the problem won’t recur.
The advantage of Coverstain is that you can use it to cover oil-based paint and then you can apply a water-based product over it. It’s therefore the perfect product to ensure a smooth transition.
03
When to Apply a Primer?
In many painting projects, applying a primer is not only recommended: it’s what will determine whether your paint will adhere properly and last over time.
Here are the situations where you must absolutely use a primer:
- After repairs with plaster or plaster of Paris.
- On a very glossy surface to improve adhesion.
- On a very porous surface (such as new drywall) to even out paint absorption.
- When transitioning from a very dark color to a much lighter color.
- On stained or problematic surfaces (nicotine, water stains, mold, etc.).
- On new wood, particularly when it contains knots.
- When transitioning between old oil-based paint and new water-based paint.
Each situation requires an appropriate primer. The table below will help you choose the right product based on the surface condition and the project you’re undertaking.
| Numerous repairs | Multi-purpose primer or Aqua-lock |
| Significant color difference | Multi-purpose primer or Bulls Eye 1-2-3 |
| Concealing knots. Plaster of Paris | B-I-N |
| Application on ceramic or melamine | Stix |
| New drywall sheet | Primer Passeport Elite: primer-sealer |
| Water stains, stains, nicotine residue | Cover Stain / Prime Lock / Seal Lock / |
| Adhesion to glossy surfaces | Stix or Cover Stain |
04
Applying a Primer: A Way to Save Time and Money
Finish paints cost more than primers. On a surface already in good condition, you can often get away with applying it directly.
However, when the surface presents a particular challenge, it is often more economical to apply a primer before painting. Since primer costs less than finish paint, you avoid multiplying paint coats to correct a problem that the primer would have solved from the start.
In the end, using the right primer can save you both time and money. You get better adhesion, more uniform coverage, and you reduce the risk of having to redo the project because the paint didn’t adhere properly.
05
Our Favorite Primers and Undercoats
We present our selection of primers that have proven their effectiveness over time. With these products, you guarantee avoiding problems!
Start your project now!
You will find all the products you need directly on our website.
- Start by measuring the dimensions of your walls to calculate the amount of primer you’ll need.
- To give you an idea, one gallon of primer will cover on average 350 to 500 sq. ft.
- Choose the right primer based on the condition of your surface.
- Place your order online and choose between in-store pickup and home delivery.
Want to learn more tips for your painting project? Visit the section of our website dedicated to this topic!
Products found in this article.
Waterborne Bonding Primer STIX
Primer-Sealer and Multi-Purpose Primer by Passeport Elite
Oil-Based Primer Cover Stain by Zinsser
FAQ
Q. How do I know if my wall has already been painted with oil or water-based paint?
A simple method is to rub a small corner of the surface with a cloth soaked in methyl hydrate (wood alcohol). If the paint softens or leaves color on the cloth, it’s water-based paint. If nothing happens, it may be oil-based paint. When in doubt, applying a primer designed for oil-to-water transitions remains the safest solution.
Q. Can a primer correct paint that is already peeling?
No. A primer improves adhesion on a solid substrate, but it cannot stabilize paint that is already detaching. Before applying a primer, you must remove all peeling paint, then properly prepare the surface.
Q. Can I apply primer only on repairs rather than on the entire wall?
Yes… but only when repairs are localized and the rest of the wall is in good condition. If repairs are numerous, if the wall shows significant differences in porosity, or if you’re making a significant color change, it’s often preferable to prime the entire surface to achieve a more uniform finish. Especially since there’s a risk that the color will be different where you applied a primer.
Q. My primer is dry. Can I wait several days before applying the paint?
In most cases, yes. However, if the wall accumulates dust, grease, or contaminants during this period, paint adhesion could be affected. If the surface has been exposed for a long time or appears dirty, light cleaning before finishing is recommended.
Q. Is white primer always the best choice?
Not necessarily. For certain significant color changes, a tinted primer can offer better coverage and reduce the number of finish coats needed. This is particularly the case when transitioning from a very dark color to an intermediate or bright color.
Q. What happens if I use the wrong primer?
The result is not always immediate. In some cases, the paint will appear perfect for a few weeks before problems appear: loss of adhesion, blisters, stains reappearing, or premature peeling. This is why choosing the primer is often more important than choosing the paint itself when the substrate presents a particular difficulty.
