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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions.

wall sizing - new plaster



 
 
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  #1  
Old March 3rd 10, 11:05 AM posted to uk.d-i-y
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Posts: 58
Default wall sizing - new plaster

Hi All,

Just wondered if anything has changed over the years - I always
understood that new plaster needs to be sized with PVA or equivalent
before painting etc., failure to do leads to peeling later on. Uneven
peeling at that, I've seen this so many times its unbelievable, there
must have been loads of inexperienced painters/builders/finishers in
the past. Trouble is the problems won't show up for years, by which
time they will have legged it.

But the current builders I'm using deny sizing is needed. Why? What
has changed? Have newer emulsions made this unnecessary?

Rgds., Tom
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  #2  
Old March 3rd 10, 11:18 AM posted to uk.d-i-y
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Posts: 614
Default wall sizing - new plaster

On 03/03/2010 11:05, Tom wrote:
Hi All,

Just wondered if anything has changed over the years - I always
understood that new plaster needs to be sized with PVA or equivalent
before painting etc., failure to do leads to peeling later on. Uneven
peeling at that, I've seen this so many times its unbelievable, there
must have been loads of inexperienced painters/builders/finishers in
the past. Trouble is the problems won't show up for years, by which
time they will have legged it.

But the current builders I'm using deny sizing is needed. Why? What
has changed? Have newer emulsions made this unnecessary?

Rgds., Tom


Most recommendations seem to be for thinned non-vinyl emulsion for first
coat straight on to dried plaster. Some sheds do it ready to apply.
  #3  
Old March 3rd 10, 01:50 PM posted to uk.d-i-y
external usenet poster
 
Posts: 183
Default wall sizing - new plaster

Tom wrote:
Hi All,

Just wondered if anything has changed over the years - I always
understood that new plaster needs to be sized with PVA or equivalent
before painting etc., failure to do leads to peeling later on. Uneven
peeling at that, I've seen this so many times its unbelievable, there
must have been loads of inexperienced painters/builders/finishers in
the past. Trouble is the problems won't show up for years, by which
time they will have legged it.

But the current builders I'm using deny sizing is needed. Why? What
has changed? Have newer emulsions made this unnecessary?

Rgds., Tom


Bare plaster needs to be sized, although your reasons for doing so seem to
differ from the actual reason.
paper shouldn't peel regardless of whether the wall was sized or not -
sizing simply kills the suction of new plaster, making it easier to 'slide'
the pasted paper into position without the wall drying it out too much
during hanging.
Painted walls don't generally need sizing because they are effectively
already sealed.

If your new plaster is being left raw, you need to size it, you can use
normal paste diluted down from the usual consistency, and allow to dry
before paperhanging

--
Phil L
RSRL Tipster Of The Year 2008


  #4  
Old March 3rd 10, 07:00 PM posted to uk.d-i-y
external usenet poster
 
Posts: 110
Default wall sizing - new plaster

On Wed, 03 Mar 2010 13:50:06 GMT, "Phil L"
gently dipped his quill in the best Quink
that money could buy:

Tom wrote:
Hi All,

Just wondered if anything has changed over the years - I always
understood that new plaster needs to be sized with PVA or equivalent
before painting etc., failure to do leads to peeling later on. Uneven
peeling at that, I've seen this so many times its unbelievable, there
must have been loads of inexperienced painters/builders/finishers in
the past. Trouble is the problems won't show up for years, by which
time they will have legged it.

But the current builders I'm using deny sizing is needed. Why? What
has changed? Have newer emulsions made this unnecessary?

Rgds., Tom


Bare plaster needs to be sized, although your reasons for doing so seem to
differ from the actual reason.
paper shouldn't peel regardless of whether the wall was sized or not -
sizing simply kills the suction of new plaster, making it easier to 'slide'
the pasted paper into position without the wall drying it out too much
during hanging.
Painted walls don't generally need sizing because they are effectively
already sealed.


I understood he was asking about painting walls ..not papering.

If your new plaster is being left raw, you need to size it, you can use
normal paste diluted down from the usual consistency, and allow to dry
before paperhanging


Mike P the 1st
  #5  
Old March 3rd 10, 07:34 PM posted to uk.d-i-y
external usenet poster
 
Posts: 3,574
Default wall sizing - new plaster

On Mar 3, 11:05*am, Tom wrote:
Hi All,

Just wondered if anything has changed over the years - I always
understood that new plaster needs to be sized with PVA or equivalent
before painting etc., failure to do leads to peeling later on. Uneven
peeling at that, I've seen this so many times its unbelievable, there
must have been loads of inexperienced painters/builders/finishers in
the past. Trouble is the problems won't show up for years, by which
time they will have legged it.

But the current builders I'm using deny sizing is needed. Why? What
has changed? Have newer emulsions made this unnecessary?

Rgds., Tom



If emulsion is put onto new plaster, the plaster sucks the liquid out
of it, and the liquid contains the pva glue that sticks the paint
pigment on. So you get a weaker bond of paint to plaster.

There are 2 ways to address this.
1. Paint first with paint diluted 50/50
2. Paint first with just water, and after 5 minutes apply full
strength emulsion.

Both work fine, I find the latter much quicker.


nt
  #6  
Old March 3rd 10, 09:22 PM posted to uk.d-i-y
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Posts: 526
Default wall sizing - new plaster

On 3 Mar, 11:05, Tom wrote:
Hi All,

Just wondered if anything has changed over the years - I always
understood that new plaster needs to be sized with PVA or equivalent
before painting etc., failure to do leads to peeling later on. Uneven
peeling at that, I've seen this so many times its unbelievable, there
must have been loads of inexperienced painters/builders/finishers in
the past. Trouble is the problems won't show up for years, by which
time they will have legged it.

But the current builders I'm using deny sizing is needed. Why? What
has changed? Have newer emulsions made this unnecessary?

Rgds., Tom


Size before papering, but not before painting.

I'd start with thinned emulsion if painting.

There's loads of discussion and information on this group, and almost
every other DIY group or forum on this, just search for "new plaster".
Loads of controversy over how much to thin the paint by, and what
paint to use, but consensus that you don't PVA plaster if you're going
to paint it.

Cheers
Richard
  #7  
Old March 4th 10, 09:50 PM posted to uk.d-i-y
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Posts: 565
Default wall sizing - new plaster


"Tom" wrote in message
...
Hi All,

Just wondered if anything has changed over the years - I always
understood that new plaster needs to be sized with PVA or equivalent
before painting etc., failure to do leads to peeling later on. Uneven
peeling at that, I've seen this so many times its unbelievable, there
must have been loads of inexperienced painters/builders/finishers in
the past. Trouble is the problems won't show up for years, by which
time they will have legged it.

But the current builders I'm using deny sizing is needed. Why? What
has changed? Have newer emulsions made this unnecessary?

Rgds., Tom




as others have said a 50:50 thinned first coat of emulsion will do.

Formulations of paint change

 




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