Is undercoat / sealer necessary for new plaster?

In message , Steven Campbell writes

You should apply a "piss" coat first. So called because the paint has been watered down so much it is as thin as piss.

Basically, first coat, any cheap old emulsion mixed approx 50/50 with water.

I've had luck with some rooms where one piss coat and one proper coat was all that was needed, others needed a piss coat and two proper coats. (all these rooms done by the same plasterer).

One thing I've never got away with though is plaster coving. Always seems to need a gazillion coats regardless.

Hth Someone

Think I heard mention a while ago about sealing the plaster first with a

There have indeed been mentions of using PVA (in various dilutions, etc.) on new plaster. Many of them also ask why the emulsion coats are peeling off...

As already said - piss-coat following by decent quality coat(s).

Hi Steven

The others are all right. I think the problem lies elsewhere. Is the different texture between the old and the new plaster giving the appearance of a different shade? in which case you will need to go over it all with lining paper. Or maybe the existing paint on the existing plaster is leaching through the new and discolouring it, this would happen if it were yellowed for example with nicotene. Just some thoughts.

Really it takes a LOT of paint, and heavily pigmented paint, to get the same color on new plaster as old.

One reason I use farrow an ball almost exclusively. Even THAT takes three coats tho.

Thanks folks for the suggestions.

I think your suggestion above about the texture being different, which makes the new plaster appear a different colour is spot on. After 4 coats I think the room is now acceptable. Although I can still see the difference, any visitors I have asked have struggled to notice it ;o)

Cheers again

Steven.