Found this on here:http://www.simplifydiy.com/painting-and-decorating/paint Sealing a newly plastered wall
It is essential to seal a newly plastered wall with either diluted emulsion (50:50 emulsion/water) or PVA adhesive solution (60:40 PVA/water) to bind the plaster surface and prevent future coats of paint from soaking into the wall
this has been covered loads of times before,use acrylic primer,wasting your time diluting emulsion paint if painting on too a solid wall.go too a paint shop and explain your painting new plaster walls and they will give you acrylic primer sealer
We recently had a building job done which left us with a lot of raw plaster. OH bought a primer/sealer in woodies can't remember the name but can ask if you need it. It cost approx 40e but as my OH said most of the plaster in kitchen area and he didn't want paint peeling off the wall in 6 months because we took a shortcut. He mixed with water and slapped on with a pasting bruchy. It was also an undercoat so we only actually used 2 coats of emulsion once it dried