It’s called “surface preparation” folks. And it’s critically important especially if you are painting a light color over a dark color. Take the exterior of your home for example.
The usual recommendations from your neighborhood retail paint expert will tell you that on most surfaces that are unpainted you should always use a primer coat plus two paint topcoats of your chosen color. You might also consider this same procedure if you’re dealing with a painted surface that requires some scraping and repair work, as well.
It pays to know the difference between latex and glossy paint. If your home exterior surface is in pretty good shape, any high-quality latex paint over an oil or latex surface works well. Just make sure you hit only repaired or scraped places with some primer, not the entire area. On the other hand if its latex paint over high-glossy paint make sure you use a primer over the whole area, not just in spots. And if you’re painting over redwood or cedar, you’ll need an oil-based primer to insure that the surface is sealed correctly to prevent “bleeding” stains.
Here are a few professional tips and suggestions on why primer is so important:
** Priming the surface is cost effective. Saves money and using excess paint
** If you don’t use a primer, the first coat will soak through to the new sheetrock
** Primer is required in order to create a “bond” with the surface being painted
** Primer gives your chosen paint color a reliable surface to stick to and seals the surface that you are painting
** Not using primer when suggested by your paint shop will haunt you sooner or later
** Primer helps the regular and cheaper paint adhere to a surface without peeling
The consensus is that primer provides the base for good adhesion; ergo, prime everything.