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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. |
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#1
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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 |
#2
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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
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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
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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
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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
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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
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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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