If you want your mural installation to go flawlessly, it’s important to make sure the surface of your wall is well prepared ahead of the actual wallpaper hanging. One of the things that often gets recommended is to apply a primer. What exactly is a primer? What are its advantages and is it necessary to apply a primer coat before wallpapering?
The purpose of a primer coat is to prepare a surface for the subsequent application of paint, wallpaper, tiling, plaster, or anything else. The primer penetrates into the surface, lowering its level of water absorption, trapping dust, reinforcing the surface, and increasing the adhesion of other materials to it. Personally, we’d always recommend priming your walls before hanging your mural — the mural will attach itself better to the wall and less paste will need to be applied to the wall (as the wall will absorb less paste).
There are a few cases where you should be careful using a primer. Fresh wall plasters need to dry, and that takes about a month. Even when not using a primer, it’s not recommended to hang your wallpaper on fresh wall plaster. Before you apply the primer, the wall should be free of any grease or dust. Holes and cracks should be filled. It’s also wise to remove any old paint — the primer penetrates the wall roughly 1mm deep. It’s also not suitable to apply a primer under strong sunlight.
Keep in mind that if the wall surface is highly absorbent, it’s necessary to apply the primer multiple times (of course this depends on how diluted the primer is with water). To apply the primer you should use a brush or a roller. A primer can take 1 to 12 hours to dry and once dry, it is transparent. For less absorbent wall surfaces, you can dilute the primer by adding water (be sure to first check the how-to instructions on the product label). Also, don’t prime at temperatures lower than 5° C (41° F).
You can add a small amount of paint into the primer (up to 10% of the volume) which will allow you to see where the primer has already been applied on the wall and to smooth out any colour differences on the wall.