Firstly the question will be about the surface or wall that you need to paint. Has it previously been painted, is it flaking, grimy, or a dark colour?
So let’s first look at a wall that has not been painted previously
All newly plastered wall should be sealed with a suitable primer/sealer. Priming a wall is vital to a lasting finish and a great-looking room, but there are also sound economic reasons for a good priming job. If you buy a good quality Top Coat, you don’t want to see stains or discoloration bleeding through because you didn’t take the time to prime. Also, primer is cheaper than paint, so if you do a coat of primer first, you save money.
What about previously painted walls?
Most importantly you want to ensure that the wall you are painting is clean, dust-free, with no flaking or damp. Wash the wall to remove any grease (we recommend sugar soap available from most hardware stores), fill any holes and cracks with one of our Skimming Products like PlasterFix. Give the wall a light sanding and remember to wipe with a damp cloth after sanding. Apply one of our Plaster Primers to the filled areas—priming will seal the filler and keep it in place. You might want to sand and re-prime the whole wall to avoid a patchy look.