Joe in Edmonton and Pat in Vancouver both asked if they could change their stippled ceilings to smooth ceilings.
This is a real tough job and my standard response is to scrape off the high points and simply put drywall over the stipple rather than trying to do a full wall plaster job. But it can be done.
In fact we went to one house with curved ceilings and large plaster moldings that would get lost of you tried to cover anything with drywall.
First a rough sanding of the stipple to reduce the easy to sand high points. Extra sanding over cracks to make room for fibreglass mesh.
Second a rough coat of plaster applied in one direction, followed by a good sanding at 90 degrees to the plaster application direction.
Third a levelling coat of plaster applied 90 degrees to the first coat, followed by good sanding across this application.
Fourth a finish coat applied 90 degrees to the second coat, followed by a final sanding. Lots of elbow grease, lots of sweat, lots of dust -- but beautiful smooth ceilings.