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Is undercoat / sealer necessary for new plaster?



 
 
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  #1  
Old February 24th 08, 10:33 PM posted to uk.d-i-y
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Posts: 137
Default Is undercoat / sealer necessary for new plaster?

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.




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  #2  
Old February 24th 08, 11:23 PM posted to uk.d-i-y
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Posts: 143
Default Is undercoat / sealer necessary for new plaster?

2 mist coats will suffice to seal new plaster when dry
  #3  
Old February 24th 08, 11:48 PM posted to uk.d-i-y
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Posts: 152
Default Is undercoat / sealer necessary for new plaster?

In message , Steven Campbell
writes
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.



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

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

I've had luck with some rooms where one **** coat and one proper coat
was all that was needed, others needed a **** 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
  #4  
Old February 25th 08, 12:22 PM posted to uk.d-i-y
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Posts: 106
Default Is undercoat / sealer necessary for new plaster?


"somebody" wrote in message
...
In message , Steven Campbell
writes
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.



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

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

I've had luck with some rooms where one **** coat and one proper coat was
all that was needed, others needed a **** 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
50 - 50 mix of PVA and white emulsion.


  #5  
Old February 25th 08, 01:01 PM posted to uk.d-i-y
Rod
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Posts: 2,893
Default Is undercoat / sealer necessary for new plaster?

diy-newby wrote:
"somebody" wrote in message
...
In message , Steven Campbell
writes
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.


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

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

I've had luck with some rooms where one **** coat and one proper coat was
all that was needed, others needed a **** 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
50 - 50 mix of PVA and white emulsion.


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 - ****-coat following by decent quality coat(s).
--
Rod
  #6  
Old February 25th 08, 03:09 PM posted to uk.d-i-y
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Posts: 164
Default Is undercoat / sealer necessary for new plaster?

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.
  #7  
Old February 25th 08, 03:14 PM posted to uk.d-i-y
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Posts: 9,056
Default Is undercoat / sealer necessary for new plaster?

Rednadnerb wrote:
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.
  #8  
Old February 26th 08, 10:54 PM posted to uk.d-i-y
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Posts: 137
Default Is undercoat / sealer necessary for new plaster?

"Rednadnerb" wrote in message
...
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.


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.


 




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