Paint Primer: For Successful Painting Results
For a successful result when painting you will often need to prime the surface first. There are a number of primers available; find out what they are and where they should be used.
A primer performs a vital function in any paint system, sealing the surface to which it is applied (so subsequent coats don’t soak in), providing a good key for the next coat to be applied and sticking securely to the bare surface so that the layers of paint don’t simply flake off. Its not a permanent protection for the surface it’s applied to, and should be covered with undercoat or top coats as soon as possible.
Most primers are solvent-based; the exceptions are some acrylic primers and primer/undercoats, which are water-based and therefore very quick-drying.
The governing factors in deciding whether or not a primer is needed are the surface to be decorated and the type of paint to be used to finish. They also help establish the type of primer required.
Bare wood should always be primed. Prepare the surface by applying shellac knotting to knots and resinous patches to prevent bleeding. If the wood has been treated with creosote, use an aluminium sealer before applying a standard wood primer.
Prime all metal surfaces regardless of the finishing paint. Apply the primer as soon as the surface is prepared to prevent the development of rust. Zinc chromate primer is the most versatile type as it can be used on both aluminium and galvanized iron.
Walls and ceilings
If the surface is porous, prime with a coat of thinned emulsion paint. This can also be used on interior surfaces like wallpaper which are having an oil-based paint finish; use an oil-based primer on other surfaces. Exterior surfaces like powdery rendering or surfaces to be painted for the first time require a stabilizing primer or masonry sealer.
Painted surfaces require priming in the odd areas where paint has been removed. If it is chalky or coated with bituminous paint a coat of primer is needed. Scrape or wash off old distemper and apply primer to an interior surface; stabilizing primer to an exterior one. For drains with a thick coat of bituminous paint use an aluminium spirit-based sealer to prevent staining.