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It's been years since I have had to paint new plaster. I can't find any paperwork or notes on any job in the past that I have had to prime and paint new plaster. So, my question is this:

What would you recommend as a primer for new plaster? By new I mean it is a new plaster skimcoat, but has dried/cured for over 9 months. My first instinct would be an acrylic primer like BM FreshStart.

Any numbers as to material usage? I know it will be more porous than drywall, but how much? 50%? 100%? Anyone with a typical sq ft of coverage for new plaster?

Any help would be appreciated.
 

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I've used BM super spec latex, and I've also used BM fresh start oil based. Both performed well, but the oil made me feel more protected, simply because it's oil.

Coverage for new plaster is scary. I'm not sure exactly what it is, but for me it's been as low as 150-200 per gallon. When you put the paint on, you'll know exactly what I'm talking about.
 

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PWG, I had a link about this, but can't find it. There's definately ways to treat new plaster, even plaster that's cured for 9 months.

The dusty porosity tends to make coatings peel. I'd thin a first coat of primer and then use a straight second coat of primer.

or maybe check out the idea of an emulsifier to get a nice bond.
 

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In the UK we have alot of plaster.
We usually thin down our first coat of matt emulsion (Latex I beleive you call it) about 20-25%.

This seals the plaster for subsequent coats.

Only use matt emulsion to first coat (seal) NEVER silk,gloss or eggshell finishes they contain too much vinyl.

If you put any paint straight (no thinning) onto new uncoated plaster you're looking for trouble.


Great forum btw.
 

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After all the problems I have had - I will be investigating those concrete type penetrant sealers - they are 100% acrylic with absolutely no pigment and are watery - I think unless the plaster job is absolutely perfectly hard trowelled - that any other latex with pigments, just won't recombine the chaulk and soft plaster. IF you are willing to wait months like 3-4, an oil based enamel undercoater with a slow dry works great.
 

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Anything for masonry should do the trick for your initial coat, but I'd watched that the moisture content was in an acceptable range and it had cured properly.

I've never painted over fresh interior plaster.

Stucco exteriors have usually been at least a week, and usually two or more, before we applied any paint to them... and we've just used exterior latex, usually sprayed. But that's probably different.

I suppose I'd use SW Loxon for a primer in a new interior situation.
It would be a hi-dollar gig, here in ca...

Labor intensity, skill to apply plaster efficiently, and cure time are probably the factors that led us to sheetrock interiors.
 

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Again - Cover Stain is an oil based primer, and works great - but you have to wait anywhere from 60 to 90 days for the plaster to completely cure and bleach out bright white. But I definitely think that is the only proper way to treat plaster - I have not had any success with latex primers that say you can prime anywhere from 3 days to a month after the job is done.
 

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I am a plasterer as well as a painter. Plaster has a 30 day cure time prior to priming. If you want to avoid the 30 you can opt for 7 days but if you do you will need to use SW Loxon designed for new plaster. Loxon has about the same PH as plaster and absorbs into the plaster. Loxon is very costly but not as costly as putting anything else on the plaster prior to the 30 day cure.
 

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Finally a plasterer who says you can't prime before 30 days. Foil - I have a question for ya - have you seen other guys in your field not 'trowelling-up' the plaster very well? Basically plaster is soft - I tested a couple of patches with latex primer and oil after 2-1/2 months - and the latex primer comes off with blue tape - where as the oil primer doesn't. But after I rip the blue tape off - I see plaster residue on the tape.
 

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Priming Plaster

Sherwin Williams ...PrepRite ProBlock int/ext latex primer sealer 1.40 mls.

Pratt & Lambert......Suprime "12"interior alkyd wall primer 1.50 mls.

Benjamin Moore..... Super Spec latex En under & primer sealer .1.10 mls.

ICI Paints......Prep & Prime Gripper multi- purpose water based primer sealer ..1.90mls

Take our pick


Plaster New
 

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Saying plaster is like saying paint. What kind of paint? Oil, latex.....Same with plaster. What kind of plaster? Lime, Gypsum, what was used as aggregate? Was it lime with a gypsum guage finish?
Lime (From limestone) should cure. Gypsum sets quicker and can be painted quicker. A LOT of lime guys use gypsum for guaging which helps it set quicker. Problem there is water and gypsum dont go well together. Depending on the mix, this could be why your latex failed. Too much gypsum used and maybe too soon. IMO.
 

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If you go over Lime plasters with latex you run the risk of peeling, gypsum plasters also have many problems in these cases. Gypsum plasters are used in homes but its most wide use in mold making.
Over the years I have tried many many primers over plasters and the best I have found is Loxon by SW, ProBlock is a great primer but over raw drywall and not so much plaster.

Painter Jeff,

What cure time for these primers?
 
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