New plaster emulsion is not taking the ****. Normally you have to wait 4 to 6 weeks after plastering before you paint it so that it's totally dry. If you don't, you trap the moisture in the plaster and get efflorescence or mould.

New plaster emulsion is special (microporous, I believe) and allows moisture to evaporate from the plaster through the paint. So you don't have to wait the 4 to 6 weeks. Nice.