My wife is an artist, so when we needed an interior wall plastering she did it, using her pottery plaster (not plaster of Paris). When we told a friend he laughed and suggested we get some wall plaster from a shop. What's the difference? Just cosmetic/cost/ease of use, or is it actually a bad thing to have on our walls?
How dose it look? Probably a little more expensive your way but I doubt there is much difference once dry.– Ed BealJan 17, 2018 at 23:21
Is it for plaster veneer, or building up a base coat on lath? Either way I think plastering a wall is art form. How do you think it turned out? Regardless of what your friend says?– freshopJan 17, 2018 at 23:22
1I bet the wall mud is a lot cheaper than what your wife usually uses.– Paul LoganJan 18, 2018 at 3:23
@freshop we took our internal chimney breast back to bare-brick (although there was also some very powdery old plaster there too), and she pva-glued it all then plastered over that.– simonalexander2005Jan 18, 2018 at 13:05
@EdBeal it looks fine, if a bit rough-and-ready. I just wanted to make sure there wasn't any difference in the plaster that would cause problems later on– simonalexander2005Jan 18, 2018 at 13:06
Up until the turn of the twentieth century, lime plaster was always used for interior applications. Gypsum plaster, which is what plaster of paris is, was only used in decorative applications, but gradually replaced lime plaster as it was much faster to put a house up with it. Lime takes some time to cure, as it cures by chemical reaction with the carbon dioxide in the air. Gypsum cures by evaporating moisture (drying).
Lime is by far the superior material. Gypsum plaster has neither the beauty of lime plaster nor the durability, nor the alkalinity to repel mold, mildew, and other house ailments. If you cover it with latex paint, you can't tell the difference, if you want something truly gorgeous use lime wash to color it. An unpainted lime plaster wall feels like polished marble and is very hard. Gypsum is very soft.
Now to more directly answer your question, compound bought from Home Depot, etc. has a lot of binders, drying agents, and other material in it. Straight gypsum does not. I'd not expect it to last very long.
1Gypsum crystalizes it cures also, you are thinking of all purpose joint compound... which just drys. May 3, 2021 at 18:39
The finish layer of plaster early 1900's was lime and gypsum (gauging plaster), and pottery plaster is actually very similar to gauging plaster. If you combined water mixed pottery plaster, with equal part lime putty, you'd have something very similar to the existing plaster. Though it would take at least 3 weeks to cure, because of the lime.
The main difference between gauging plaster, pottery plaster, and plaster of paris is the coarseness of the mill. So the setting time, is the majority of the difference. There are also differences in quality of gypsum of course, which effects the harness. In the case of pottery plaster, the quality would likely be superior, and produce a harder surface.