NH,
I have used it before. But just on repairs on our house. I never really bothered to measure the coverage. I also used it to make a bread oven, made of dry stacked bricks and sealed with plaster.
So I am aware of the need to build it up in layers.
But here I am making a room of certain dimensions, and for figuring costs I need to know how much plaster it will take to cover the walls and ceiling.
My plan is to have a base coat, at least one build coat with the final build coat given a wet sponge rub to make it even -this also gives it a grainy texture. It will then be finished with a lime wash to make it smooth, because this will be a comercial cheesemaking room and Indiana law requires that such facilities have smooth walls that are easily cleaned. I chose to go with lime plaster for its antibacterial properties.
I will try a test patch to estimate coverage, that is a good idea. I have some old plaster I can use. Hydrated lime works well, provided you use it quickly. It will break down over time once exposed to air and no longer make good plaster.
For Hydrated lime, I use a 3:1 ratio of sand to lime, mixed on a board with a shovel.
