A.Ron Webber, owner of Prime Plastering in Irvine, Calif., responds: In the center of the ceiling, where there is no particular need to be fussy, you can beat out the plaster fairly quickly. When you get to the edges, use a large screwdriver or chisel to chip away the plaster more carefully, so as not to damage the adjacent surfaces. You want to leave a clean edge in the corners, if possible. Where necessary, use metal snips to cut the lath.

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