Newly plastered ceiling???

Miss_Laid

27col wrote: »

What is the fascination on this forum for putting pva everywhere?

I was told to mix up a solution of 4 parts water 1 part pva and 1 part paint and do 2 coats with that, it was the plasterer that said it

andrew-b

Then your plasterer doesn't know what his talking about and should really know better!

Plasterer's use diluted PVA on the walls BEFORE plastering which is one of the acceptable uses of PVA...AFTER isn't. The only time PVA on fresh plaster would be acceptable is if your papering on top of it - though then really you should be sizing the wall with wallpaper paste..not PVA.

The reason you shouldn't use PVA is when PVA gets wet it converts back to liquid form (why it's used as glue for kids as it can be washed off hands, clothes, furnishings etc!).

It's all about surface chemistry..when you paint over it the paint will be adhering to the PVA which the diluted PVA solution will have left over the surface. Any moisture content left in a freshly plastered wall/ceiling has to go somewhere and heads to the surface..PVA sucks it up and the adhesion of the paint to the wall is broken and your paint comes flaking off (like washing it off your fingers!). If that happens it's alot of work to make it good again and your freshly plastered surface may never be as good a finish again.
Similarly if it's in a room that suffers alot of condensation such as a steamy bathroom or kitchen the moisture may go the other way and again off comes your paint!

If the wall is totally dry and not in a room subject to condensation you might get away with it but not recommended to risk it! This time of year it could take months for plaster to fully dry so it's even riskier. Bearing in mind how much it cost for plastering, a tub of the right type of paint for a couple of mistcoats is generally a small price to pay!