Primer, also known as undercoat is the first product that any renovator should apply to a wall before painting.
By blocking a base, the primer allows maximum adhesion of the paint for an optimum finish.
What is a primer?
This is a preparatory coating applied to materials before painting. The primer ensures better adhesion of the paint to the surface, increases the durability of the paint and provides additional protection for the material to be painted.
A primer generally consists of 20-30% synthetic resin, 60-80% solvent and 2-5% additive. Some primers also contain polyethylene for extra durability.
Why use a primer?
The primer is a paint product that allows the finishing paint to adhere much better to the substrate than if it were used on its own. It is designed to adhere to surfaces and form a bonding layer to receive the paint.
In practice, primer is often used to paint porous materials, such as concrete and wood. The use of a primer is considered mandatory if the material is not water-resistant and will be exposed to the elements. Priming plasterboard (drywall) is also common practice in new construction, as it seals the wall against moisture and can prevent mould growth. Primers can also be used on dirty surfaces that cannot be cleaned, or before painting light colours over a dark finish.
Some primers can be tinted to match the colour of the finish paint more closely. If the finish paint is a deep colour, tinting the primer can reduce the number of coats of finish paint needed to achieve good uniformity across the painted surface. Primers are also used to hide joints and seams to give a finished look.
Some primers require the topcoat to be applied within a certain time after the primer has dried to ensure optimum adhesion. This period varies from 24 hours to two weeks after the primer has dried. Painting after the suggested time may result in performance problems depending on the particular situation. It is common practice to apply the top coat of paint before the primer is completely dry to improve adhesion between the primer and the top coat. The level of exposure, for example indoors or outdoors, can affect the importance of applying the topcoat within the specified time.
How do I choose my primer?
The choice of undercoat depends on the type of paint and the condition of the substrate. For acrylic paint, for example, choose an acrylic primer.
There are a number of different primers to meet specific needs, such as:
- Indoor stains and odours
- New drywall
- Areas prone to damp
- Repaired walls
- New bare wood interior
- MDF panels
- Interior joinery already painted
- Drastic change in paint colour
- Exterior wood
- Old exterior paintwork
- Exterior wood that stains
Ask your paint retailer for advice before renovating.
Airless spray printing
You can use a conventional brush and roller to print your walls, especially as the undercoat doesn’t require an ultra-perfect result. However, we’d also like to show you how to apply a primer simply using an airless spray gun.
In the video below, you can see an interior print using the Graco JetRoller airless roller. Unlike traditional rollers, the JetRoller is attached to an Airless station via a flexible hose.
It pumps the material and sprays it directly onto the roller, saving you a lot of effort compared with a conventional paint roller!
Source: Facebook page Entreprise Julien.
Now that you know how to choose the right primer, we recommend that you read our complete dossier on which paint to choose for my interior renovation, as well as our articles on finishes:
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