Is undercoat / sealer necessary for new plaster?

[Steven Campbell]

After having some plaster work done I thought there would nothing else to do
but give the walls a few coats of white emulsion. However after the 3rd
coat, I can still see a difference of colour from the old plaster to the new
plaster.

I've still to do a couple of walls where there is old and new plaster on the
same wall.

Is it worth putting undercoat on first? Would it make a big difference?

Also would it be worth while applying the undercoat to the walls I have
previously painted that the new plaster can still be seen?

Steven.

[ALex]

2 mist coats will suffice to seal new plaster when dry

[somebody]

In message <13s3s6k...@corp.supernews.com>, Steven Campbell
<sp...@privacy.net> 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

[diy-newby]

"somebody" <in...@somewhere.co.uk> wrote in message
news:nnjaZrX2...@somewhere.co.uk...

Think I heard mention a while ago about sealing the plaster first with a
50 - 50 mix of PVA and white emulsion.

[Rod]

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).
--
Rod

[Rednadnerb]

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.

[The Natural Philosopher]

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.

[Steven Campbell]

"Rednadnerb" <bhar...@hotmail.co.uk> wrote in message
news:7ba6656e-cb9f-419a...@s13g2000prd.googlegroups.com...

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.