How to rectify paint going straight on to plasterboard

Zinnser is excellent but expensive 99% of the time an oil based undercoat will do the same thing by sealing the substrate and applying a seal over the stain professional painters like to use zinger as it dries quick and can be painted over in under an hour but if you have the time ,save money and buy a litre of undercoat ,thin slightly with white spirit and apply over the affected areas following day just re apply your emulsion or if you really want a durable finish apply a satin oil based paint

hello Reason it occurs is when the initial coat of paint on the new plaster is bog standard silk applied undiluted directly to the plaster. Solution: On old plaster doing this – give it a light sanding and apply a thinned coat of matt paint – thinned with water to make it sloppy. Allow to dry thoroughly and then paint as usual. On new plaster – the plaster should be given plenty of time to dry. Don’t rush this process. Once dry, the first coat of paint on the new plaster should be matt (preferably white) and it should be thinned with water so that it is sloppy. Paint all the plaster with this mixture. It is your undercoat. It will sink into the surface of the plaster and give you a sound base for painting. Allow to dry. Won’t take that long because it will soak into the new plaster. Paint on another coat and leave to dry – Overnight. Now, you have prepared the plaster for painting and will avoid bubbling and peeling in the future. Paint in the colour of your choice. Very good and the lasting solution is to use Zinsser BIN. First remove all peeling of paint and sanding surface before use the Zinsser with two coats.

Hi you will need too scrape as much paint as possible off the ceiling only leaving the bits that won't come off then use white Matt paint and mix with water and pva to help seal the bare plaster and bond the edges of the bits of paint that won't scrape off . You will need to use filler to flush off the edges of the bits of paint you couldn't get off after filling give the filling a sand . Then use any kind of oil based paint to seal the yellow water marks or a product I like to use is zinnser cover stain it comes in a convenient spray can or you can get tins of the stuff you can apply by brush . After this 2 coats or vinyl Matt emulsion of the colour you want