by rosebery »
Wed Jul 08, 2009 10:16 pm
Its patchy for one of two reasons:
1. The plaster wasn't properly dried out before you painted it. It doesn't dry evenly so some paint on dry stuff and some on not so dry - hence patchy. How long after the plasterer had finished did you leave it before painting? Was it just a skim?
2. You don't have an even layer of paint over the whole ceiling. Because you used the paint neat then it went on too thickly making it difficult to get an even coat.
Silk finish doesn't stick too well to new plaster anyway so a coat of oil based undercoat won't solve any potential adhesion problems that you may have had because the substrate was still wet/damp or paint was too thickly applied.
Paint For New Plaster as a retail product is marketing hype. A mist coat of matt emulsion (though NOT rich matt) would have been fine first.
SBs suggestion has some merit as if it is a plaster issue the patches may disappear as the plaster completely dries.
If it were me (which it isn't and so not my decision) I'd scrape the whole lot off before it cures fully (about 30 days), mist coat with supermatt or vinyl matt, second (but still diluted) coat of matt then on with the silk.
Cheers