Should first coat of paint on freshly plastered ceiling be watered down?

Hi, Yes first coat on Plaster should be watered down approximately 50/50 if you use quality emulsion (Dulux / Crown) for example. For cheaper paint 60% paint 40% water. Thanks Tom

Yes he is correct, the 1st coat should be thinned with water, depending on the quality and thickness of the paint IE: Dulux, Crown is quite a thick paint and will need to be diluted by up to 50% or more. So only dilute enough to cover the new area plastered, it's called a mist coat, this will then act as a primer for the remaining 2 coats which again if Dulux or Crown will require 10% of water. If you don't thin down the 1st coat and it is applied too thick it WILL flake and peel. Hope this is of use, I used to lecture painting and decorating at the local college. Feel free to ask any questions. Best Wishes Andy.