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What tools do I need for plastering a wall
- Thread starter ive
- Start date
rlitman
Well-known member
Sandable 90 IS plaster. It has lime and other chemicals added to slow its cure time to 90 minutes, and has perlite added to make it sandable and lighter. It's a great product, and easy to use. Faster mixes get more difficult to work with.I can use the sandable 90 on plaster? Do I use a hawk or a trowel for that?
A hawk is used to hold onto extra plaster while you work, and help you work with a trowel (though I like to use one with a spackle knife). You don't touch the walls with the hawk.
Just a nit: the hot mix drywall compounds are gypsum ( plaster of paris (calcium sulfate hemihydrate)) based. they contain limestone (calcium carbonate) powder as a filler, but not lime (calcium hydroxide). The plaster of paris reacts with water to form gypsum (calcium sulfate dihydrate), with the limestone and other fillers glued together with the gypsum. That forms a reasonably monolithic surface, which can range from almost rock hard to scratch with finger nail soft, depending on what fillers are present. t'he lack of lime makes them easier to work with (lime is very caustic.)Sandable 90 IS plaster. It has lime and other chemicals added to slow its cure time to 90 minutes, and has perlite added to make it sandable and lighter. It's a great product, and easy to use. Faster mixes get more difficult to work with.
A hawk is used to hold onto extra plaster while you work, and help you work with a trowel (though I like to use one with a spackle knife). You don't touch the walls with the hawk.
Traditional white coats are lime based. The lime reacts with carbon dioxide from the air, and turns into calcium carbonate. That's slow (days, potentially), so they usually are mixed with plaster of paris (in the form of 'gauging plaster') for faster setting. These finishes are rock hard, and if applied well, glass smooth (I've scraped paint off them with a razor and not damaged the underlying surface).
Have a case in my fridge.Your gonna need a big can of moxie.
rlitman
Well-known member
Agreed. The amount of lime I was referencing is quite small. Probably a few tablespoons per bag, but enough to adjust the working time, where the 90 has more than the 45.Just a nit: the hot mix drywall compounds are gypsum ( plaster of paris (calcium sulfate hemihydrate)) based. they contain limestone (calcium carbonate) powder as a filler, but not lime (calcium hydroxide)...
You're absolutely right that the lime isn't "filler". Yes, the filler is largely powdered limestone and talc. The more perlite (what I mentioned) they add, the rougher the surface texture, but perlite makes it super easy to sand, and lightens it quite a lot. It's why these hot-mix compounds make for a crappy top coat. Structo-Lite in the brown bag has quite a lot of perlite, making it much better if you're starting from scratch on the lath and need to put up that first 1/2" or more, but the surface ends up as rough as brushed concrete.