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amakarevic 01-12-2013 04:16 PM

painting new plaster
 
i have made significant indoor plaster repairs (as i calculated it was simpler and cheaper than framing + DW) and now i need to paint it.

the question is: what should i do to prep it for the paint? is regular primer OK or should i use something else (or in addition and in which order). i have heard some emulsion is needed but i am not very familiar.

thanks

Brushjockey 01-12-2013 04:36 PM

- Must be brit- there ar different products over there- but best I know a good acrylic primer /sealer ( like zinsser 123) would work fine for priming- but somewhat depends on what you intend for final finish.

amakarevic 01-13-2013 01:50 PM

Quote:

Originally Posted by Brushjockey (Post 1091943)
- Must be brit- there ar different products over there- but best I know a good acrylic primer /sealer ( like zinsser 123) would work fine for priming- but somewhat depends on what you intend for final finish.

I am in the U.S. -- it's just that the house is old. I want just a regular wall that is painted like the most regular wall. flat enamel, white.

Brushjockey 01-13-2013 02:25 PM

You using the word emulsion rather than latex -is very brit- that's why I thought.
If you did plaster repair with modern materials ( like setting muds and joint compound) there is no problem priming right on them.
However old style limed plaster needs to be either aged or neutralized. And they do still use that over there.
Prime and 2 coats and your good to go.

amakarevic 01-13-2013 06:37 PM

i used the old-fashioned plaster recipe. for the initial two coats, i mixed 2.5x masonry sand with 1x hydraulic lime. for the finish coat, i used 1x of the same lime and 1.5x of really fine sand (quickrete makes it and was really hard to find -- had to go to a material store in B.F. Egypt to get it).

Brushjockey 01-13-2013 06:56 PM

First q- why..I have repaired miles of plaster with the other stuff..
But now you will have to neutralize- Haven't needed to do it ( in almost 35 years..) but I think vinegar will do it. Some chemist will be stopping by..

amakarevic 01-13-2013 07:13 PM

why? because someone told me. there is very little info on plaster repair out there since the technology is outdated

Matthewt1970 01-13-2013 11:13 PM

The heavy lime concentrate plaster needs an oil based primer from what I have always been told AND needs to dry for 30 days before you paint it.

chrisn 01-14-2013 04:53 AM

[QUOTE=Matthewt1970;1092994]The heavy lime concentrate plaster needs an oil based primer from what I have always been told AND needs to dry for 30 days before you paint it.[/QUOTE]


at the minimum

chrisn 01-14-2013 04:56 AM

Quote:

Originally Posted by amakarevic (Post 1092772)
i used the old-fashioned plaster recipe. for the initial two coats, i mixed 2.5x masonry sand with 1x hydraulic lime. for the finish coat, i used 1x of the same lime and 1.5x of really fine sand (quickrete makes it and was really hard to find -- had to go to a material store in B.F. Egypt to get it).

quote" I am in the U.S. "

I have not had my coffee yet( not allowed, off topic) but what am I missing here?:huh:

Brushjockey 01-14-2013 06:34 AM

as usual- the humour ( see what i did there! - probably not..)

:laughing:

ric knows paint 01-16-2013 07:46 AM

Quote:

Originally Posted by amakarevic (Post 1091927)
i have made significant indoor plaster repairs (as i calculated it was simpler and cheaper than framing + DW) and now i need to paint it.

the question is: what should i do to prep it for the paint? is regular primer OK or should i use something else (or in addition and in which order). i have heard some emulsion is needed but i am not very familiar.

thanks

Hmmm...you're probably not aware of it, but you bring up a plethora of issues that just don't get addressed all that often anymore. Plaster, unfortunately, is not a common building material anymore (at least in most areas of the U.S.) due to the labor-intensive expense of application - plus all the other eccentricities and behavior characteristics of a substrate that can sometimes be "difficult" to hold paint over long periods of time.

To begin, plaster is a highly alkaline, masonry/cementitious coating that will require 30 days to cure before priming/painting. When plaster was a more common building material, the only primer recommended was an oil based product since latexes (of that time) were pretty much guaranteed to burn and peel shortly after application. Back in that day, painters/craftsmen used to size new plaster with a product called "Adhesium" glue size - a clear wall size that, when applied to fresh plaster, would turn pink if the plaster was still too hot to paint. This told the painter that either more cure time was necessary - or more prep was needed before applying oil based prime coat (while the "Adhesium" trade name is owned and used by the Muralo Company, I don't think the original glue size is even made anymore).

Since that time, paints have changed dramatically and the recommended products have pretty much done a 180 degree role reversal. Oil based paints (back then) were more oil - and much less alkyd than they are today. Modern day "oil based paints" are actually more alkyd and less oil, and don't work particularly well on plaster if there is any degree of moisture present (which there always is with plaster - remember, it is a cementitous surface containing soluble salts that hold water)...Alkyds applied to an alkaline surface, with moisture present, will result in saponification (making soap) that causes alkyds to peel in sheets.

At the same time, latexes have changed even more dramatically. Back then, latex paints were pretty lousy products. They had a hard enough time adhering to innocuous, inert surfaces - let alone the more "difficult" surfaces such as plaster. The "latex" products of today don't even use the same type of resins that were used back then - the only similarities are their ability to dry fast and clean up with soap and water. Todays acrylics have outstanding adhesion, and are pretty alkali resistant (that's not to say surface prep isn't necessary for new plaster)...and today's acrylic primers hold their purchase to new plaster far longer than the old oil based products from many years ago.

So...to finally answer your question, allow your plaster to dry 30 days. After 30 days, your plaster should be hard and relatively slick. I've always believed the best prep for plaster is to scuff sand with medium grit paper, followed by sponging the surface with a mild vinegar solution. Unfortunately, the vinegar solution then needs to be neutralized with clean water and allowed to dry before priming. The vinegar wash neutralizes surface alkalinity - plus slightly profiles the hard plaster for better adhesion of the prime coat. A vinegar etch may be unnecessary, but it's easily applied and may actually prevent problems down the road.

There are many brands of acrylic primers that can be used for new plaster (and there are other types of primers beside acrylics that will work) - Zinsser makes BullsEye 123 (acrylic - my recommendation), or Cover Stain (modified oil), or BIN (pigmented shellac)...each would work, and each can be found in most paint stores or hardwares. Talk to your local independent dealer for his recommendation of product brand that'd work best in your application - and good luck.

Brushjockey 01-16-2013 07:51 AM

ric's always good for the straight up info! there you go.

jsheridan 01-16-2013 01:52 PM

Zinsser claims that Gardz has a high alkalinity resistance and can be applied to fresh plaster within days. What is your opinion of that Ric, and does that mean it would be a barrier for a latex or oil topcoat? By the way, good to see you.

ToolSeeker 01-16-2013 04:47 PM

Hey Ric you been on vacation.


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