Yes you need to prime this surface before a finish paint is applied.

You will need to go to the paint store and ask for an acrylic primer, sometimes it is called acrylic undercoater but it will great for this type of wall surface. You need 100% acrylic rather than just latex because of the alkalinity in the plaster. Then you are ready to apply the finish paint og you choice.

plaster must be allowed to fully cure (at LEAST 30 DAYS) before priming.

Personally I wouldn't use a water-based product for first prime.

Hi Guys,

100% Acrylic Latex is correct for priming; and yes, waiting a month is appropriate.

Also, because plaster mixing ratios vary a little, DON'T rule out 2 full coats of primer!!

* Those walls can be very thirsty with some plasters.

* Even with 2 primecoats, TWO coats of actual paint are required.

Faron

I might be wrong but I doubt that plaster is realy used over the blue board but it most likely is just wallboard compound applied over the entire surface.

I have no idea what was used in this case.

But the whole purpose of blue board is to be used as a base for veneer plaster systems.

I've just finished a skim coat of Diamond Finish Plaster. This is my third room, so I've made most of the mistakes already noted and would like to get the priming/painting part right the first time. The USG technical notes say I should use an 'alkali-resistant primer/sealer'. Great...looks like there's lots of good product available in the U.K. and Europe. How about here in the States? My local paint store said Z-Prime II should work over plaster, but I'm not convinced. Suggestions?

You will want to use an acrylic primer as that is the most alkali resistant. A good choice would be the Ben Moore Regal Acrylic First Coat # N216. I would think that one coat of primer follow by two coats of finish paint would work very well and you can't go wrong with the Ben Moore regal finish paints.

Thanks 5slb6. Always appreciate a specific suggestion. My prior experience was that the plaster sucked up a bunch of primer, and due to inadequacies in the product or with other mistakes of my own, the result was paint lift-off and ongoing adhesion problems. So, any primer that allows me to do fewer coats and does the right kind of chemical sealing would be great. Will head on down to my local Benjamin Moore store next week.

You are very welcome.

The Regal line of finish paint will be a good choice for a topcoat, and it comes in flat,matte,eggshell, pearl and semi-gloss.

Hope all goes well with your project.