Calcamine...unless completely removed try the following recipe: Scrape all loose paint and chalky areas, wipe clean with TiteBond, prime with shellac based pigmented primer such as BIN. Once you have primed with shellac, recoat with a high quality alkid/oil primer such as Ben Moore's FreshStart UNDERBODY sandable primer. Then apply two coats of a high quality 100% acrylic finish paint. Good luck...this extra work will insure years of trouble free ceilings.