If you are going to paint something, you need to know whether it requires priming in preparation. Depending on what you are painting, primer has a few different functions. Our guide below helps to explain where a primer is required and the type of primer to use.
Do I Need A Primer?
If you are painting a porous material, such as new wood, plaster or plasterboard, you will always need a primer. If you are restoring an object and have stripped the paint off it, a primer is a good base for new paint. If something is stained, the right primer will cover the stain and stop it from bleeding through to the top coat.
A primer is always needed to paint shiny surfaces such as metal, plastic or tile, so that the paint will adhere to the glossy surface and not just peel off.
Priming Wood Surfaces
New wood should always be primed prior to painting. This is to seal it, stopping the paint from being absorbed, and to stop any moisture from getting in to the wood. Priming new wood will also stop any tannins from coming through and discolouring the paint.
Look for a primer which says it is for wood, and make sure it is suitable for the type of wood you are painting. Hardwoods and softwood have different properties, and will absorb primers in different ways. Manmade woods such as plywood and chipboard are different again, but can usually use the same type of primer as a softwood.
Acrylic Primer Undercoat is a basic, fast-drying primer suitable for non-resinous softwoods and manmade woods. It is suitable for both interior and exterior use.
Oil-based or Alkyd primer is a basic wood primer suitable for interior and exterior use. Usually complies with BS regulations – check the tin to confirm this.
Aluminium primer is required for resinous woods, hardwoods and woods that have been treated with a preserver. It is self-knotting and can be used indoors or outdoors.
Priming Walls And Ceilings
New plaster or plasterboard need priming, as they are extremely porous. See our project on Painting New Plaster for more help with this.
Priming Plastic, Tile, Glass And Melamine
Any glossy, non-absorbant material will require a specialist primer to make paint adhere to it, otherwise it will just peel off the shiny surface.
Priming Metal Surfaces
Different metals have different properties, but a universal metal primer will work on both ferrous and non-ferrous metals, as well as inhibiting rust and reducing risk of corrosion.
Red Oxide primer should be used on metal that will rust if exposed to cold air or humidity.
Stains And Problem Surfaces
Stabilising Solutions can be used to prime surfaces that are especially porous, or have a loose, powdery finish, such as plaster and masonry. An Alkali Resisting Sealer should be used on lime-based plaster, concrete and cement.
Stains such as smoke and nicotine can be sealed in with special stain-blocking primers. Mould paint or fungicidal solutions should be used to prime walls that have been subject to organic growth such as mould and algi.