To prime or not to prime

boongywoongy

Just started a rip out to refurb our bathroom. The walls had 3 coats of paint that came off nicely to leave bare plaster that is in pretty good nick.

My question is, do I need to prime the walls before I apply the two coats of bathroom paint? If so, what product is good and not too expensive?

FreeBear

With wall paint, the usual advice is to thin some of the paint (50:50 paint:water) and give fresh plaster a mist coat. Or you could use Zinsser 1-2-3 - Slap on a thinned down coat, and when dry, another coat at full strength.

If you consult the paint supplier, they will tell you if a specific primer is recommended.

Grenage

Always prime bare plaster.  I normally use a 50:50 mix of the cheapest white emulsion.

sammyjammy

boongywoongy said:

Just started a rip out to refurb our bathroom. The walls had 3 coats of paint that came off nicely to leave bare plaster that is in pretty good nick.

My question is, do I need to prime the walls before I apply the two coats of bathroom paint? If so, what product is good and not too expensive?

What do you mean it had three coats of paint that came off to reveal bare plaster?

ButterCheese

Bare plaster will absorb any moisture in fresh paint, so if you paint directly on top with new paint it will suck the moisture out and the paint will flake, and not stick.  So you need to wash it first with (as others have said) either watered down paint, specific primer, or watered down PVA glue.  The plaster absorbs this mixture which then seals up the pores of the plaster, so you can then paint over it.

Grenage

ButterCheese said:

Bare plaster will absorb any moisture in fresh paint, so if you paint directly on top with new paint it will suck the moisture out and the paint will flake, and not stick.  So you need to wash it first with (as others have said) either watered down paint, specific primer, or watered down PVA glue.  The plaster absorbs this mixture which then seals up the pores of the plaster, so you can then paint over it.

Aye, although PVA should never be used before paint. Before skimming or filling is fine.

FreeBear

Grenage said:

ButterCheese said:

Bare plaster will absorb any moisture in fresh paint, so if you paint directly on top with new paint it will suck the moisture out and the paint will flake, and not stick.  So you need to wash it first with (as others have said) either watered down paint, specific primer, or watered down PVA glue.  The plaster absorbs this mixture which then seals up the pores of the plaster, so you can then paint over it.

Aye, although PVA should never be used before paint. Before skimming or filling is fine.

Quite a few plasterers are switching to SBR or a specialist acrylic primer now rather than using PVA.

danrv

For bathroom bare plaster, I did a mist coat, Zinsser Gardz then top coat.

Grenage

FreeBear said:

Grenage said:

ButterCheese said:

Bare plaster will absorb any moisture in fresh paint, so if you paint directly on top with new paint it will suck the moisture out and the paint will flake, and not stick.  So you need to wash it first with (as others have said) either watered down paint, specific primer, or watered down PVA glue.  The plaster absorbs this mixture which then seals up the pores of the plaster, so you can then paint over it.

Aye, although PVA should never be used before paint. Before skimming or filling is fine.

Quite a few plasterers are switching to SBR or a specialist acrylic primer now rather than using PVA.

I did look at trying some SBR, but I've still got 4 litres of PVA!

FreeBear

Grenage said:

FreeBear said:

Grenage said:

ButterCheese said:

Bare plaster will absorb any moisture in fresh paint, so if you paint directly on top with new paint it will suck the moisture out and the paint will flake, and not stick.  So you need to wash it first with (as others have said) either watered down paint, specific primer, or watered down PVA glue.  The plaster absorbs this mixture which then seals up the pores of the plaster, so you can then paint over it.

Aye, although PVA should never be used before paint. Before skimming or filling is fine.

Quite a few plasterers are switching to SBR or a specialist acrylic primer now rather than using PVA.

I did look at trying some SBR, but I've still got 4 litres of PVA!

Had to throw the last can out as it had started to smell and gone lumpy. Even if stored in a cool spot, shelf life is around 12 months.

boongywoongy

sammyjammy said:

boongywoongy said:

Just started a rip out to refurb our bathroom. The walls had 3 coats of paint that came off nicely to leave bare plaster that is in pretty good nick.

My question is, do I need to prime the walls before I apply the two coats of bathroom paint? If so, what product is good and not too expensive?

What do you mean it had three coats of paint that came off to reveal bare plaster?

We didn't like the lumps and bumps on the wall so we used a scraper to remove the existing paint on the walls. When we did this with scraper, there were clearly at least three different colours of paint. It all came off reasonably well and now the walls are back down to grey plaster.

Based on the comments, I think that we'll be applying a couple of coats of mist paint as a primer.

Thanks for all the comments.