Try priming first and then patching over the primer. It could be that the patching itself isn't adhering well to the walls underneath. You also want to be sure the walls are clean and dull before applying primer.

1) What "speed" of joint-compound did'ja use?

2) What exact primer brand/series?

Another possible issue:
>>> Many people seem to "over-roll" the paint or primer...meaning-going back over the SAME area too many times.
* After a couple minutes, many primers have SLIGHTLY skinned over and wetted joint-compound areas (if latex primers used).
* If this area is rolled into again, it hasn't even remotely bonded to the wall yet, and will get pulled off by the pressure and fresh primer going back over this area.
* Solution-
Roll on a FULL COAT of primer. Don't even remotely push it too thin!
* After 2 or 3 hrs., primer should be dry enough to apply paint.
* Your compound felt "muddy" after priming because it was "re-wetted" by the primer. Compound may also have still been a little wet.
* FULL bonding of primer AND paint-layers to themselves AND the wall takes a couple weeks!!!

Faron

Thank you both for your replies.

paintguy - I don't think that's the problem because the joint compound seems to be sticking very well to the walls. It's that the primer is pulling away from the jc.

Faron - I used 45 for the top coat (joint compound) and the primer is Zinsser Primecoat2 Primer Sealer. I suspect that your "possible issue" is dead on. I have been trying to roll the primer on "not too thick" and find myself pushing it and spreading it. I tend to go over the same area over and over to "even things out." The peeling actually never happens after the first pass, but I have definitely noticed that if I try to fix a peeling area by going over it again, I only make more of a mess. Your description of the problem and the solution sounds like my answer! Thanks.

I finished priming a bedroom. It looked fabulous! Then, I noticed a hairline crack in one of the corners where the ceiling and wall met. I picked at it with the corner of a drywall knife. I started to scrape and noticed that the knife could go under the primer and very easily peel away big pieces! I figured this was a problem that needed to be dealt with before applying paint, so I started spot checking the room by gouging the primer with a sharp putty knife and then seeing if I could scrape it off the wall. I noticed that especially over areas where there was joint compound, the primer would peel off very easily. I also noticed that the back of the primer was "dusty." The jc on the wall was now also chalky, but was not that way before I primed. So, now IÂm thinking that I did something wrong with the jc, or maybe there was a problem with it or the primer. I went down to the paint store and they told me that I should never have dust under the primer and it will never hold. He told me to scrape all my walls and ceiling and start all over again, this time using an oil-based primer. Then I started wondering, what if this is actually normal for a water-based primer. I have to admit, I never in the past tried slicing and scraping a freshly primed wall before. Today I called the primer manufacturer. They told me that I should have left it alone. They said that the primer never would have peeled on its own and of course it will come off the wall if I stick a putty knife under it! Am I a totally neurotic dunce who is only looking for trouble?

Is it, or is it not normal for joint compound to feel more chalky after applying primer and then removing it (maybe no one will know because who the hell picks brand new primer off the wall when it looks good)?

Does the primer just form a "skin" over the walls or is it supposed to actually fully bond with the wall?

How long does it take for the primer to fully bond to the wall (or cure)? The support guy from Zinsser said that it may take a week, but it has been at least a week since I put the primer on.

What are the possible causes of little cracks in the primer almost exclusively in the corners? I am thinking that maybe it was applied too thick since I was using a rather thick brush.

Yes, paint will crack in corners if it is applied too heavily. Primer will also grip better as it cures, but this doesn't mean that you have to wait until until it cures before you can topcoat. Sometimes in bathrooms or older houses with poor insulation or some other issue, paint drying can take a long time. If it can't dry, then it is not going to bond as quickly. Drywall compound is basically a big pile of compressed dust when sanded, so it is pretty normal for there to be dust on the back of the paint chip if you peel it off.

Paintguy -
I don't want to put words in your mouth, but it looks like you are saying that there is nothing abnormal about the fact that I was able to slide a putty knife under the primer and easily peel away large pieces. If I just left it alone, probably everything would be okay?

I'm not saying that there isn't a problem. But, it could be that the paint is not cured enough for it to be adhered as well as it should be. Does that make sense? What happens during the curing process (which could take up to a month even in good drying conditions) is that the paint grabs hold better and better the more cured it is. I am certain that if I painted a room, I could peel that paint off an hour later if I wanted to. Now, I realize that your primer has dried a lot longer than that, but if there is some reason the primer is not drying, then the primer could act as if it was recently applied.

Yeah, I understand what you are saying. The room is a just a regular bedroom - low humidity (in fact lots of forced hot air coming through the heating vents) - so I don't know of any reason why the primer would not dry or cure as it should. The walls look perfectly fine (other than the hairline cracks that I saw in a few places in the corners and the "testing" that I did). So, it's been at least a week - is there any way to know for sure if the primer is adhering as it should? I really feel stupid, because I suspect that there was nothing wrong to begin with and being able to peel the primer off doesn't necessarily prove anything.

You could take a chip and have it tested, but I know that would be a huge pain. One way to tell for sure if the primer is stuck is to paint over it with your topcoat. Just do a small test area at first. The new paint will put stress on the primer layer, and any primer that is not adhered will probably bubble.

I have experienced the same thing many times. I think one of the earlier commenters got it right. When you apply the primer to the joint compound you can only do a once over, you can't go back and forth or the primer will pull itself off along with the joint compound.

I've experienced this too. It's frustrating for sure. I suspect it's a combination of all the above described causes, back rolling areas with joint compound and dampness with joint compound, PVA-based primer, etc.

Were you "skim coating" the entire wall? If so, you would have been better off with a drywall primer, rather than a general wall primer such as 123 or Kilz2. Drywall primers are designed primarily to wet down and bond to the drywall and mud. To this extent, it has much less pigment than a full bodied, general purpose primer.

Would have been better off using Gardz