DO I NEED TO PRIME

Priming is a term most people know, but when painting internal walls it is generally referred to as sealing the walls rather than priming. Interior acrylic (water based) sealers are generally used as a sealer / undercoat, here are some of the main reasons for using primer / sealer on your walls.

All new plaster board / drywall should be sealed with a suitable primer/sealer.

If your existing paint is chalky then is should be washed first, then primed/sealed. Once paint has gone chalky it is at the end of its live and has started to break down. Using a primer/sealer will help bind back the existing coat and make a sound surface for your final coats.

If you are changing from oil based paint to acrylic paint then give the walls a good sand and then apply a coat of acrylic sealer/undercoat.

Note: You can not use acrylic paint over freshly painted oil based paint, it will not adhere to it.

All cracks and holes that have been patched using a patching compound should be primed/sealed after they have been sanded.

If you are changing from a dark colour to a light colour then a coat of primer/sealer  would be advised because most likely you will need an extra coat to cover the dark colour. The primer/sealer will help, without going into a lot of detail, its better to apply one coat of  primer/sealer first.

If you are using a bright colour then you should start with you walls being white or grey. A bright yellow over lets say a dark blue will never cover, there are some colours that need a pure white base and I mean a pure white base, it may mean that you will need to paint over the existing colour a few times with white to achieve this.

There is away that may help you work out what colours may need a white base coat and that is from what base they are made from (all paints colours are made from different standard base colours), bright or light colours made from any other base than white may need a white base coat. An example of this would be a yellow tinted from a white base, now it should cover ok but if you have a yellow made from a deep base then your in trouble, you will need a white base before you apply the top coats. Consult your paint shop but make sure they know what they are talking about as I have met a few over the years that don't really know much about paints.

I personally made a mistake recently, it was a bright red and I used a grey undercoat and I should have used white undercoat. I was curious what the manufacture said about this colour and if there was any specific colour I should use for an undercoat. Their reply , remember this is the manufacture, there was no specific undercoat colour required and that a white or light grey undercoat would be fine. I can tell you my undercoat was a little darker then light grey but I'm sure pure white is the only undercoat that should be used with this red. Why I didn't use white to start with is because the owner of the house had used the colour on a few doors themselves with a white undercoat, looking at it you could see the white through the red. After I had made my mistake I took another look and come to the conclusion they had just put the paint on too thin and that was why the white was still visible in some area's

How To Prime A Wall

This video demonstrates how to prepare and prime new plaster board or drywall.