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How to mix plaster
Prepare the wall for plastering.
Before you get started, make sure the wall you're finishing has already been, and any seams have been touched up with a base coat. That way, all you'll have to worry about is spreading the plaster, which will require your full attention.
Plaster is best applied to wood or metal lath, or bare walls stripped of paint and wallpaper. If the wall has semi-gloss or gloss paint on it, you should prime it before adding plaster.