Primer on plaster
Should you paint primer on plaster? It really depends on what paint you are using, what type of plaster you have, and what finish you would like.
Does all plaster need a primer?
Yes, all plaster needs something to help it bond the main thick top coat emulsion paint to the plaster itself. The plaster, whether old or new, is very absorbent, so when you paint your thick top coat emulsion paint directly on, it dries so quickly it forms more of a skin than a adhesive bond, which can lead to your paint bubbling and peeling in the future.
Using primer on plaster walls allow you to create that bond, so your top coat sticks properly to your plaster.
When To Paint New Plaster
I suggest you wait at least 4 weeks before painting your new plaster, but please check your plaster, or check with your plasterer (also it depends on what time of the year and how warm it is!)
If you have just had fresh plaster, or just had a reskim, you must wait until your plaster is properly dried, which can vary in speed. Ideally check with your plasterer or it’ll be written on your bag of plaster you have. Usually it’s around 4 weeks in warm weather and just a few days for a thin light skim. Err on the side of caution here and leave a little longer than you need to be safe!
So, whether your plaster is freshly dried, or old and dry, the next stage is the same.
Mist coat or primer?
Before you paint your top coat you can either use a dedicated plaster primer, or you can use what’s called a mist coat. In simplest terms, a mist coat is just a water thinned coat of your top coat that you paint a single layer on, which soaks into the plaster and grips in. When you then paint your top coat over, the top coat grips to the mist coat, which in turn is deeply gripped into the plaster itself.
What kind of paint can go straight onto plaster?
Lots of paints can go straight onto plaster as long as you water thin the first coat, to act as the mist coat. I don’t advise you to ever paint your thick topcoat undiluted directly onto bare plaster, it’ll just peel off given half a chance.
We love to use the Auro 555 Natural Emulsion paint for all walls or ceilings, and yes, just mix 10% water to 90% Auro 555, and use this as your single coat of mist coat (or bare plaster primer), and then 1 or 2 undiluted coats as your 'top coat'. Read here as to how to paint a wall.
Should I use PVA to seal plaster?
No, please don’t. Just don’t. There is no need. It was just used to prevent paint from cracking as the plaster dried. But the reality is if you just wait for the plaster to dry (which you should be doing) and then use a mist coat or plaster wall primer you won’t have any problem at all.
How do I prepare plaster before painting?
Prepping fresh plaster
If it’s fresh plaster it’s pretty much ready to go, mix up your mist coat or your plaster primer and apply a single coat.
Prepping old plaster
If it’s old plaster, I’d give it a bit of a light sand to make the surface a bit more even, as you’ll have shiny spots and rougher spots, which can show through the paint if you’re not careful. The more time you spend prepping the plaster, the better the resulting finish will be.
If you have old plaster, you will likely have old holes and imperfections, which you can fill with a natural non toxic wall filler such as the Auro wall filler.
If you don't have bare plaster, but plasterboard, have a read of this FAQ on plasterboard primer paint choices.
What type of primer to use on new plaster
Check out some of the following Plaster primers
We also have all primers and wood primers
