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masonry heater plaster question  RSS feed

 
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I am finishing up rebuilding my masonry heater. There are multiple reasons why I don't believe I can plaster it with lime. Mainly time: I need to start using the stove in the next week or so here in Ohio. Would using a gypsum plaster be a reasonable thing to use? I can't find much info on it. If so, would I simply go to the hardware store and buy it in the bucket? The same stuff I would use to cover taping when putting up drywall?
 
gardener
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Location: Upstate NY, zone 5
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I don't see drywall spackle being a good finish, it's soft enough that it would take damage easily. I think gypsum plaster takes time to cure properly too, maybe not as much as lime (not sure) but still probably longer than you want to wait for heat. What is the prospect for leaving the plastering to spring? Would there be domestic mutiny?
 
Ian Schwartz
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I should mention that my heater is double skinned, so anywhere the plaster will go won't get terribly hot. I didn't put a thermometer on it last year, but I'm guessing it won't be over 200 degrees F
 
Ian Schwartz
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Haha well, my family is forgiving, but I really want something on it. I could maybe do an earthen plaster. I have enough lime wash in the garage that I could paint it with that to clean it up and limit dusting. Then maybe lime plaster in the spring. Main time constraint I see is making the lime putty. I know you should let that soak for as long as possible. But, would I regret only soaking for a night or two? If I could do that, maybe I could get it done in time. I saw a story on the mha website that said lime plaster was often applied to a warm stove historically. But, that seems to go against any other advice I can find online. Any suggestions of how to get a lime plaster on it within about a week time constraint would be really appreciated. Any other ideas also, of course. Thanks
 
Glenn Herbert
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The first bag of hydrated lime I got had full instructions, and didn't say that a long wait was necessary. I did let that one sit for several months before using it. A day seems to be acceptable, from what I read, even if longer slaking is better. I think one thing it does is give a finer finish, which is not relevant for a scratch coat. Putting plaster on a warm stove would minimize surface cracking, as the stove would have expanded a bit and would put the plaster under slight compression.

I have read that a month of dampish curing is best for lime plaster, but don't know how much strength you would lose by only having a week before heavy heating and drying.
 
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A thin (less than 1/2") layer of gipsum plaster will be dry in a week.
 
Ian Schwartz
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Peter,

Any advice on a gypsum plaster recipe?
 
Peter van den Berg
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Gypsum plaster of Plaster of Paris consists of dehydrated gypsum and probably some additions as well. What I would do is buy the stuff, in Europe I would use Knauf Redband or a similar brand. I am unsure about what is available in the USA, maybe it is branded as drywall plaster or something like that. I wouldn't dream of making the composition myself.
 
Glenn Herbert
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I have seen it in the US as skimcoat plaster, basecoat plaster, possibly veneer plaster. You just want to avoid anything labeled spackling compound which dries rather than sets.
 
Ian Schwartz
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Great thanks for the help guys
 
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