# Plaster primer



## DeanV (Apr 18, 2007)

Looks like most of the plaster primer stuff is 4-5 years old know. We still have a plaster guy who really wants oil primer on the stuff. Looking at BM's TDS sheets, they recommend 023 or 046 acrylic primers before their oil stuff. And if oil, they want a 30 day cure. I have a 1 week cure window.

It looks like a pH of below 10 is enough for application of the BM stuff, how quick do limed plasters like Snowdrift take to fall below pH of 10?

Other option is just to spec Loxon which is good after a 7 day cure and pH below 13.

Thoughts on plaster primers with modern thin coat plaster systems?


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## paint-ability (Nov 29, 2011)

I've had good results with Glidden's Gripper. Up to 13 ph. At $24 a gallon its a good deal


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## Stonehampaintdept (Jan 10, 2013)

A quality 100% acrylic is going to be the most forgiving prior to 30 days. I think oil is going to be out of the question, unless you can convince them to wait 30 days. The longer the better with plaster. I agree Moores 023 or California's 503-00. here's the spec sheet. http://www.californiapaints.com/uploadDocs/1/Spec/50300-PCALL-SURFACE-ACRYLIC-PRIMER.pdf

Failing will be worse than waiting.


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## plainpainter (Nov 6, 2007)

Not only have I primed plaster, I've also done quite a bit of veneer plastering myself. The quickest I've ever been able to prime plaster with oil was 45 days - and that was during the winter months. I've had mucho failures with plaster and latex/acrylic primers, especially if I didn't wait a long time. 2 weeks is my minimum wait time with a latex primer. To be honest, any paint on plaster that happens prior to a 3-4 month wait is just a hack. Most folks shouldn't get plaster because they aren't willing to work with it. You should really wait til plaster bleaches out bright white before priming/painting. I've seen some plasters take over a year before that happens. It's worse if the plasterer puts a bunch of retardents into his mix.


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## DeanV (Apr 18, 2007)

Is pH the fail safe measure of when it is ready? Moisture content? Or some mystical unmeasurable quality?


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## 6126 (May 9, 2010)

I dont think I've seen anyone prime plaster with oil in years. But, then again we dont have much out here compared to you guys back east.


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## mudbone (Dec 26, 2011)

Zinssers Gardz sealer claims that freshly applied plaster can be extremely alkaline with a ph of 12 or more in many cases.New plaster should be allowed to cure 24 hrs. before applying their product.The old calcimine plaster coating for many years were sealed with oil base primers.Gardz penetrates calcimine more effectively than oil base coatings and much less odor.Because Gardz resist moisture and whatever finish you decide to coat over it with will not soften up calcimine layers underneath.


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## plainpainter (Nov 6, 2007)

mudbone said:


> Zinssers Gardz sealer claims that freshly applied plaster can be extremely alkaline with a ph of 12 or more in many cases.New plaster should be allowed to cure 24 hrs. before applying their product.The old calcimine plaster coating for many years were sealed with oil base primers.Gardz penetrates calcimine more effectively than oil base coatings and much less odor.Because Gardz resist moisture and whatever finish you decide to coat over it with will not soften up calcimine layers underneath.


When it comes to plaster, ignore the labels and do what is right. 24 hours is a joke! I've had plaster jobs where I waited 3+ weeks before priming, and the plaster was in awful shape. Had to vinegar rinse it, and still had primer failure, or really just plaster failure.

If you have a great plasterer that doesn't F' up his mixes with retardents - you can prime with an 100% acrylic primer like Muralo's 2205 in about two weeks after application. Most jobs I've seen, you'll have to vinegar rinse the plaster, wait 3 months, and then use a long dry interior oil primer, or BIN. But no homeowner wants to hear that. I had a bad batch of plaster that I used in my own home. I waited 120 days for it to cure, used Behr's 100% acrylic primer that I got as an extra on another job - and had adhesion failures where the paint was closest to the baseboard radiators.


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## plainpainter (Nov 6, 2007)

DeanV said:


> Is pH the fail safe measure of when it is ready? Moisture content? Or some mystical unmeasurable quality?


 No, no, & no. The only failsafe is you have to look at the plaster, it has to bleach out bright white before it's truly ready to prime and paint. The problem is that this use to happen like 30-60 days after the plaster was put up.

Now a days, I've seen plaster jobs go over a year before bleaching out. I've tried ignoring my own experience and go with recommendations from paint companies - and I have had failures every single time. If you don't have failures, it's because you didn't really try to see if the paint is sticking or not. Where as I've come to peoples' homes 11+ years after it was built and could pull sheets as large as poster boards right off the walls. 

If I had to work with plaster again, I'd experiment with those newer urethane modified latex primers that stick better.


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## plainpainter (Nov 6, 2007)

mudbone said:


> Zinssers Gardz sealer claims that freshly applied plaster can be extremely alkaline with a ph of 12 or more in many cases.New plaster should be allowed to cure 24 hrs. before applying their product.The old calcimine plaster coating for many years were sealed with oil base primers.Gardz penetrates calcimine more effectively than oil base coatings and much less odor.Because Gardz resist moisture and whatever finish you decide to coat over it with will not soften up calcimine layers underneath.


The problem with plasters, especially 'limed' plasters, is that they are about 30% Calcium hydroxide, that's the 'limed' part of the plaster. Sound familiar? Ever heard of Potassium hydroxide or Sodium Hydroxide? Yeah, all really really high ph stuff. Back in the old days, they wouldn't even attempt to paint the stuff, they'd put wallpaper over it instead, and they'd use Calcimine water paint on the ceilings - because that's the only thing that would stick! I've painted a ton of homes, and have never come across a calcimine ceiling that wasn't already gone over at least 50 years ago and cracking apart like mad. And we're talking about new plaster anyways.


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## DeanV (Apr 18, 2007)

From what I have read today and talking to BM yesterday, oil is not good since it will have a saponification reaction if the plaster is too hot still. Oil required the longest wait to apply primer. 

Plaster guys like oil because it looks good right away, but failure comes a few years down the road as the reaction occurs over time. This makes sense with all the older bubbling plaster ceilings we see that the brittleness of the paint shows it all is oil and failing.

With acrylics, if it is too hot or wet still, you will see blushing right away, mottling, or pin holes. Blushing and mottling can be fixed by a vinegar wash to lower the pH (I would think better to measure the pH first and wash then or wait longer). Pin holes need to be filled by the plaster guy.

If you think about every other masonry surface we paint, specs say NOT to use oil due to pH. How come ONLY plaster is the one masonry type surface that conventional wisdom says to use oil? Every other high pH surface says do not use oil/alkyd primers (apart from a few odd ball high pH tolerant alkyds, but those are not the typical oil primers).

Dan, for the plaster you are talking about, is it thin coat or old school style? This is newly finished thin coat/skim coat plaster. The plaster is Snowdrift autoclaved finish lime. I plaster and lathe applications would definitely need longer due to the thick layers involved.


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## plainpainter (Nov 6, 2007)

Dean I am talking new style thin veneer plasters, in my area we use Uni-kal which is a 'limed' veneer plaster. The reasons why you don't want to use a latex primer with plasters range from mineral salts that can bleed right through it, just not that great of adhesion, especially if the plaster job is 'soft'. 

I've seen many latex/acrylic primers eventually just de-laminate from plastered walls. While it's true that plaster is too hot for oil based primers. The fact is if you wait for plaster to bleach out bright white - then it's safe to use an oil primer. An oil primer will hold back staining from mineral salts, will not re-introduce moisture into the plaster, just plain sticks better, and will based on many tests I have done in the past to measure adhesion, will recombine a loose crumbly 'soft' plaster job which is what I have seen very often. 

If you have an A++ plasterer, and since I trowell veneer plaster myself I can tell who is the good from the bad, then you can go with a quality 100% acrylic primer 2 weeks after application. If you have a ****ty plasterer, then you'd better wash the surface with an acid/vinegar rinse, wait 3 months, then use a quality oil long dry primer.


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## workin'man (Jan 18, 2013)

try a hudson sprayer if possible to lightly wet the plaster. wet it several times a day. This will decrease the ph faster. Do a moisure check prior to paint. Talk to the plaster contractor and your paint rep and see what they think!


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## plainpainter (Nov 6, 2007)

workin'man said:


> try a hudson sprayer if possible to lightly wet the plaster. wet it several times a day. This will decrease the ph faster. Do a moisure check prior to paint. Talk to the plaster contractor and your paint rep and see what they think!


Make sure to not just use water, put a pint of vinegar per gallon of water.


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## DeanV (Apr 18, 2007)

The problem is that NO ONE agrees.

I just got off the the phone with the technical department of the plaster manufacturer and THEY DO NOT KNOW which product prime with, how long to wait, etc.


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## plainpainter (Nov 6, 2007)

DeanV said:


> The problem is that NO ONE agrees.
> 
> I just got off the the phone with the technical department of the plaster manufacturer and THEY DO NOT KNOW which product prime with, how long to wait, etc.


Dean, you gotta go with your own experience. I can only share based upon what I know, actual job experience. I don't like the fact you have to wait so long to prime the stuff - but I've tried following the manufacturers recommendations - but where are they when a failure happens? What do you do if you an entire surface then isn't adhering? 

You might get away with quicker recoat times using newer technology products, heck one painter told me he painted regal direct to plaster with no issues! Personally, I would go 'old-school' as a guarantee against failure and then try newer products as time goes by and your experience grows. My experience with even veneer plaster systems, is that unless you waint until the plaster turns bright white and you go over with an oil - then everything else is a gamble. I've had walls in my own house that went 8 months before painting. 

Plaster in my opinion is not really a very easily paintable surface, it should really be wallpapered. Walls where we took off the wallpaper with 20+ year old veneer plastered walls underneath - those walls just sucked up the oil primer and worked out awesome! 

I've done my own skimming, and used a latex primer in just 2 weeks and worked out great. But I have the experience not only painting plaster, but actually skimming it myself - I can look at it and know what and won't work. And most plaster work in my opinion is way too 'green' to paint unless you wait about 4 months. And even then it should get a vinegar/water rinse and then left to cure another couple of months.


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## DeanV (Apr 18, 2007)

I do appreciate your input. I am just absolutely amazed at the complete lack of agreement from the plasterers to painters to plaster manufacturers to young plasters to old plasters to paint company reps to....

I have never seen an issue with as much disagreement or as many questions as plaster priming.


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## DeanV (Apr 18, 2007)

As another example, USG's TDS for painting plaster says to never apply water or vinegar to the surface prior to priming as it can lead to degrading the plaster and pitting of the surface.


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## CliffK (Dec 21, 2010)

Dean,

We don't encounter a lot of *new* plaster, but when I do, I try to wait as long as "realistically possible" given the situation and go with a high quality 100% acrylic primer. I went through the same thought process you are going thru now about 12 years ago on a large high end project where even the ornate crown moldings were made out of plaster. I was very apprehensive. Ended up using the acrylic after about 10 days and never looked back. It came out fine without any problems short or long term. I have done the same ever since the few times I have encountered it with the same results.
Dan makes a lot of very good points , however in todays day & age, in my experience, with the rare exception, it becomes unrealistic to wait as long as safely necessary to prime with oil.


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## plainpainter (Nov 6, 2007)

CliffK said:


> Dean,
> 
> We don't encounter a lot of *new* plaster, but when I do, I try to wait as long as "realistically possible" given the situation and go with a high quality 100% acrylic primer. I went through the same thought process you are going thru now about 12 years ago on a large high end project where even the ornate crown moldings were made out of plaster. I was very apprehensive. Ended up using the acrylic after about 10 days and never looked back. It came out fine without any problems short or long term. I have done the same ever since the few times I have encountered it with the same results.
> Dan makes a lot of very good points , however in todays day & age, in my experience, with the rare exception, it becomes unrealistic to wait as long as safely necessary to prime with oil.


you can wait as little as 10-14 days if you use an acrylic based primer. But you better have knowledge that the plaster job was done spot on. There are quality plasterers and there are junk plasterers out there. The thing is, when your paint fails over a lousy plaster job - who do you think they're going to blame? My personal experience is that they blame the arrow and not the indian, i.e. they will blame you the painter for a paint failure.

As to the pitting, I've read that passage as well dean. I put it up there with zinnser saying not to use TSP to clean walls before using their priming products. Manufacturers all say crazy things. If it's a quality plaster job, and you use a quality stain-killing acrylic based primer - then you are potentially good to go. But for my money, if the plaster is dark looking, I leave it alone. Nothing will stick well to plaster other than a really cured out plaster.


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## painterdave71 (Jan 1, 2013)

@ Dean. It says your from Michigan... 1 state west & u could go to Hallman Lindsey paint stores as they have your solution. (if client can bend on the oil & do acrylic/latex). They have a primer/ finish coat called coincidentally "Plaster Coat". i exclusively use the plaster coat on interior plaster whether it be veneer or traditional 2coat after 2 days on "pushy/need it done in a couple of days" clients/contractors. i have work over 5yrs old & have never had a problem even on plaster that was still "wet" with adhesion or lifting. maybe check in2 a similar product with same vehicle type. (ethylene-vinyl acetate/acrylic) good luck. oh & btw b4 i get ?'d. it will need 2 coats this is self priming not the "all u need primer finish 1 coat" thats the new rave from box stores & no i have never checked ph b4 application. hope it helps.


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## caulktheline (Feb 10, 2011)

mudbone said:


> Zinssers Gardz sealer claims that freshly applied plaster can be extremely alkaline with a ph of 12 or more in many cases.New plaster should be allowed to cure 24 hrs. before applying their product.The old calcimine plaster coating for many years were sealed with oil base primers.Gardz penetrates calcimine more effectively than oil base coatings and much less odor.Because Gardz resist moisture and whatever finish you decide to coat over it with will not soften up calcimine layers underneath.



Chalk one up for mudbone :whistling2:


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## DeanV (Apr 18, 2007)

All for nothing anyway. Too high for the job. I hate it when I spend time talking to paint reps, plaster companies, read a bunch of TDS sheets to back up my decisions and product selection since it runs counter to the plaster guys ideas for nothing. Oh well. At least for the next plaster job I know what to specify without doing research again. Hopefully I remember.


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## plainpainter (Nov 6, 2007)

DeanV said:


> All for nothing anyway. Too high for the job. I hate it when I spend time talking to paint reps, plaster companies, read a bunch of TDS sheets to back up my decisions and product selection since it runs counter to the plaster guys ideas for nothing. Oh well. At least for the next plaster job I know what to specify without doing research again. Hopefully I remember.


 So just curious, what was your final decision how to tackle plaster?


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## DeanV (Apr 18, 2007)

We were going to check pH in 24 spots (minimum) and moisture meter readings. Building had 14' ceilings with only heat from a furnace in a corner (not ducted heat for even heating) and go with acrylic due to not waiting for a longer cure. We called for pH reading to be 10 or below before painting.

Planning on Loxon for primer since specs on that called for a seven day cure on plaster. We were going to try to extend the cure time as long as we could, hopefully 14 days. It would still need to pass the tests. I would use other 100% acrylic primers like to top line BM ones, but the price on Loxon is actually better.


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## plainpainter (Nov 6, 2007)

Good plan of attack, I was thinking of installing a de-humidifier in rooms for the future to make the plaster dry faster. 

I understand about moisture meter and alkaline tester, but with experience you'll see both just by looking at the plaster.


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## TrueColors (Jul 30, 2010)

Why not neutralize the plaster with zinc sulphate????


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## DeanV (Apr 18, 2007)

I have not heard of that one from any paint reps or plaster companies. Tell me more. Is it easy to apply to 8,800 sq. ft. or so of plaster?


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## TrueColors (Jul 30, 2010)

DeanV said:


> I have not heard of that one from any paint reps or plaster companies. Tell me more. Is it easy to apply to 8,800 sq. ft. or so of plaster?


I've never done it myself but it is in every painter and decorator book. It's all over the painter and decorator encyclopedia by good heart Wilcox.
Which is used in many technical trades school. Zinc sulphate neutralizes plaster in preparation for paint.

I found a article here.
http://www.empireblended.com/engineered/specialtysundry-zincsulphate.html


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## DeanV (Apr 18, 2007)

Looking into the zinc phosphate on google, I am finding articles on using it to get around the alkalinity of plaster prior to applying oil paints or primers. The references seem to all be from the early to mid 1900's (pre WWII). It looks like it is not as simple as it would sound since too little ZnSO4 is bad since the plaster is too alkaline still and too much is also bad for the oil. 

Interesting reading some old journal articles on it briefly. I will need to look into it more. I know I do not like the idea of applying water to something that needs to be painted with oil though.

With everything I read, I cannot believe not one TDS mentioned this or the plaster manufacturers.


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