One word: Calcimine! Not the end of the world, but a fairly common problem in old houses. It is an old fashioned lime-based paint that stays up pretty well, until you apply one too many (and that can be single one or x+1 coats, never can tell) coats of paint over it. After that it just sheers off, exactly as you described, with all the layers put on after it. Of course, if it sheered it completely off, that would be better, but it has a nasty, patchy way of departing which leaves the need to scrape the rest of it off. Surprisingly, and most annoyingly, the unsheered-off parts can be a bear to clean up.

Sorry to say you probably have to remove it all, and start painting, again, from scratch. I've had the best luck with using steam to get the recalitrant patches of calcimine off. There are some proprietary removers and coaters, none have really done the trick for me, but YMMV!

The good news is that it sounds like there is nothing essentially wrong with your plaster. Repaint jobs are a pain; replastering is also pain, but an expensive one, as well.

If you google up the world calcimane you'll have a barrel-full of info to noodle on. Good luck!

Molly~

Sorry, I was in a hurry before. You mentioned your plaster wasn't in the best shape. What's it like? Sometimes older homes don't have finish coat plaster, but stopped after the rougher grey coat if they intended to paper the walls. (The rougher coat makes it easier to stick on wall paper.) Occasionally people see the grey stuff and assume they've lost the finish layer when they never had it in the first place.

The other possibility to consider, if the peeling is in one area only, is whether you have some kind of concealed leak, instead of a calcimine problem. Usually, though, with a leak you see some water stains.....

M

We had the same problem. I don't know the exact source, but it may have been that adding moisture in the form of water-based paint, seeped through to loosen the under layers.

The plaster and oil-based paint in the area looked sound, but after we added a layer of latex primer, the next day, it began flaking off in huge sheets. That area was right under the bathroom, where there had been a leak, now repaired. This may have been a factor, but it didn't damage the paint.

We just removed all the flaking paint, sanded down the remainder, fethering the edges so they wouldn't show a sharp ridge. Then we used a paster primer, and painted. It held up fine.

I would make sure that there is no hidden moisture source above the wall.

(By the way, Molly, that grey scratch coat plaster makes it harder to wallpaper, not easier. We have some under the area where the wainscotting was and where a doorway was covered over. It is a real PIA to get paper to stick.)

Do scrape off all of the old paint. It will be messy and time-consuming, but you already know that everything in an old house is somewhat frustrating. Easy test for calcimine: it's water-soluable, so if the junk comes off with water, keep scrubbing! After scrubbing, let it dry for a few days, come back and prime with an alkyd primer, then do any point-up necessary. Sometimes for unforseeable reasons, the final coat of paint is too much, and it starts peeling. It can be seasonal, rising damp (if plaster is over brick), chimney-related (if the problem is near the chimney- water can enter from the top and soak the brick), or the type or brand of a previous paint job.
Casey

Here is a link that might help.

Here is a link that might be useful: calcimine

I had to chuckle when I saw the heading to this post, because I knew the answer... Yesterday, hubby and I started tackling the calcimine-coated walls in our study with putty knives, scraping off all the old peeling paint. Talk about a dusty, sweaty mess... I'm glad it's a "cheap" process, but it certainly is not easy or quick!!

The surface paint is coming off quite well in come places, but in others, we just cannot seem to get the surface layer off. (It seems to stick tightest where the surface paint is thinnest.) Tomorrow we're going to get some plastic sheeting to lay down, so I can start washing down the walls while hubby continues to scrape; I'm hoping that the water may help to loosen the remaining paint so we can get to the calcimine underneath.

Does anyone have any good suggestions for a brand/style of primer to roll on after we've gotten as much of the calcimine off as possible? I'm planning on stopping at a Sherwin-Williams store tomorrow to see what they might have or suggest, but I know some people that post here are probably more knowledgeable than their clerks might be!

As I recall, someone does make a primer just for calcimine. Google to the rescue, I bet!
Yep, "Benjamin Moore Super Spec Calcimine Recoater 306"
Casey

Well, we've been tackling the paint/calcimine dilemma for two days now, and this is where we're at:

Hubby and I have been going at the surface layer of (peeling) paint with 3" putty knives, and we've gotten about 85% of the paint off... the remaining stuff JUST WILL NOT BUDGE. This morning we went to HD and I picked up a jug of TSP, which (according to the label) is good for removing chalky substances. While hubby was up on the scaffolding, scraping near the ceiling, I started scrubbing a section of the wall with full-strength TSP and an abrasive sponge (like one would use for drywall finishing), being sure to leave a good sudsy layer on for 2-3 minutes before rinsing with a different sponge and clean water. Two scrubs/rinses seemed to cut down about 90% of the chalkiness, and it did help lift the surface layer of paint somewhat, but there are still patches of paint here and there that no amount of scraping seems to want to take off.

My question is, do we absolutely NEED to get every speck of surface paint off the walls before priming/repainting? I found the above-mentioned Benjamin Moore product via a Google search; has anyone used it before, and do you know how much wall prep is required before applying it? I am wondering how much of the calcimine it penetrates...

Whoever said this wasn't an easy project sure wasn't kidding... It's a cheap project as far as materials costs go, but BOY is it grueling...