Doing some project scheduling for complex historic restoration job. We have gypsum block walls with gypsum plaster over. We’ll be cutting channels in the walls to run sprinkler pipes and then patching the plaster over. I need to know how long we’ll need to wait for the finish coat to cure before we can paint. I know the pH should be less than 10 and moisture content less than 12%, but I need typical real world number of days it takes to get there. Are we talking a couple of days or weeks? Keep in mind this is gypsum plaster, not Portland cement plaster, which is much slower to cure.)
Thanks,
Andrew
Replies
I always heard 30 days, but I've used BIN before as a primer and painted over in about a week with no ill effects.
Mike Hennessy
Pittsburgh, PA
Everything fits, until you put glue on it.
30 days is the 'traditional, time-honored waiting period.'
Jeff
30 days is the appropriate waiting period for Portland cement plaster, which cures much more slowly, and with a very different chemical process than gypsum plasters. And that's the difficulty I'm having with this subject, as many sources lump the two together and consequently ignore the differences between the products. So I'm hoping for specific advice regarding gypsum plaster. Anyone?Andrew
My reply - 30 days - was for gypsum plaster.Mike HennessyPittsburgh, PAEverything fits, until you put glue on it.
Ok, in that case, any suggestions for specialized repair plasters that cure faster and would allow quicker painting? We're talking about shutting down a major national landmark hotel for a month for this project. Extending that to two months to allow for plaster curing is a non-starter. Surely there must be products that address this issue?Andrew
Are you not talking to the manufacturers of the various plaster products that you might use? I would start with calls to their technical departments--they can tell you what products will work and how to use them. Getting specialized technical information for a historic project on a major national landmark from strangers on an internet forum.... THAT'S a non-starter.
Well yes, you have a point there. Just trying to tap into actual real-world experience. What the manufacturer's reps will tell you is heavily salted with CYA. Some of them have come up through the trades, but many have not.
Again, I have primed with Zinzer BIN (a sealing, alcohol/shellac-based primer) after 3 or 4 days -- just enough to let the plaster set and dry well, but not fully cure -- and painted 30 minutes later. No failures to date.
The sealer keeps the alkalai in the plaster from messing with the paint.
Mike HennessyPittsburgh, PAEverything fits, until you put glue on it.
Edited 6/5/2009 12:49 pm ET by MikeHennessy