Flaking paint on a newly painted plaster wall

Question:

Wonder if you could help me, I am trying to first coat a newly plastered wall with a good brand emulsion and using a good finish roller.  I have watered the emulsion down but as the paint dries the paint just peels off.

What am I doing wrong, could it be anything to do with the roller I am using as I normally use a paint pad??

Hope you can offer some advise.

Thanks

Answer:
There are two issues to consider with new plaster. The first is a high PH level. You may have heard of this in concrete. Plaster is very similar. As the plaster dries there are a lot of chemical reactions going on that make it very alkaline. This makes normal paint unlikely to stick well if at all.

The second issue is moisture in the plaster. Just because it’s dry on the surface doesn’t mean it’s completely dry in the middle or back. Perhaps you have noticed a little extra humidity in the room?

Here is what you can do. Put a couple fans in the room with the door open for a few days to help the plaster dry. The PH level will slowly dissipate and stabilize over the first month. After that normal paint will work just fine. Prime with a PVA. If you don’t want to wait that long you can buy an alkali – resistant primer from your local paint store. Don’t forget to use a low nap roller to keep that plaster looking smooth.

Happy Painting,
Tim Hoeffel