Painting over flaking wallpaper primer

13 May 2014
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United Kingdom
I'm painting a previously wallpapered room. Stripping old ugly embossed wallpaper was surprisingly easy, but it left a thin layer of white stuff underneath, which I assume is wallpaper primer or sizing? There's a shiny layer of wallpaper paste visible on top of this.

This white layer is intact in most places. And covers about 90% of the wall. But it has come away with the wallpaper in several places, particularly in one corner of the room where its really patchy and flaky (see pics) It doesn't seem to wash off easily. I tested a small area and the wallpaper paste residue washed off but the sizing didn't budge.

I'm confused as to how to deal with it. Removing it looks like it would involve stupid amounts of washing/scraping. but likewise painting over the flaky bits doesn't seem like a good idea, and the height difference where there's bare bits would surely show up.

My current thinking is to:
Wash off the remaining wallpaper paste
Sand (hopefully smoothing the flakes)
Wash again
Apply a high build primer to take out the patchiness

Can anyone comment on this or add give any pointers? Recommendations for a primer would be welcome, preferably a low solvent one as we've got a young kid and my wife's pregnant.

EDIT: Thanks to responses below I have realised that the white stuff is the mist coat that was on the plaster which has come off with the wallpaper because we dry stripped it.
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Is it sizing for sure? If so, you could get a wallpaper steamer and melt it off - if it is made of glue, it should work. Not sure on primers, but if you want the easy option, then put up lining paper then paint.
Good luck, lots of work!
Well, the reason I asked is sizing tends to be clear, transparent where as mist coat would be white (most folk use white paint). It looks more like a mist coat to me.

I don't think washing it off will help, scraping & sanding is probably the best bet. I think zinssers do all sorts of good paint solving things, but am not sure if anything will stop the paint looking patchy when you repaint it. If it were me I'd rub it down as flat as poss then line the walls and paint over those, or remove all the white paint/mistcoat and start again - including another mist coat for bare plaster left behind. If you don't remove the white patches, when you paint they could very well lift off.

Best of luck!
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Thanks for the reply, I think you're right, it is the mist coat. Regrettably a bit more care in taking the paper off might have left it intact. Anyway, sounds like I've got more than I bargained for! This is just the box room, I've got the other bedrooms to do too, might just have get used to the awful 80s embossed wallpaper!
My guess is that you stripped the wallpwer DRY and not with a steam stripper, you have removed the original Emulsion Wall finish in patches.

Wash down the walls, sand off, fill and feather off with a fine surface filler apply a blinding coat, apply a second fill, and rub down, it may need another blinding coat, size and hang wallpaper. job done.
Your guess is absolutely correct there! In my defence it was the other half that did it :rolleyes:

Will try the advised, was hoping to paint rather than paper though. Pardon my ignorance but can you explain what a 'blinding coat' is?
Your guess is absolutely correct there! In my defence it was the other half that did it :rolleyes:

Will try the advised, was hoping to paint rather than paper though. Pardon my ignorance but can you explain what a 'blinding coat' is?

A thinned down coat of TRADE Emulsion,

I find this problem all the time, people think by stripping wallpaper (Dry) it will cut the cost of a Decorators bill for the rest of the job, it ends up making the job more expensive with filling and preparation to make the job passable. All good intentions though .
Gotcha, thanks.

You live and learn, eh? Interestingly, two of the walls are pretty much OK, even with the dry stripping. They are internal walls. It's the two outside 'brick' walls that the underlying paint has come off.
Personally I would go for Trade Polyfilla Fine Surface filler and a good flexible filling knife

assuming that it is water based paint, why not just use a steam stripper to remove the rest. far quicker than filling and sanding. Just ensure that you don't keep it on one spot for too long, otherwise you may blow the plaster.

Additionally you will need a decent stripping knife, I would go for the ones that have replaceable glades. The best I have found are the Japanese Olfa ones cheaper versions are available though.

If the paint were oil based you could use a heat gun (which will also work on the WB paint as well)
Many thanks for all the replies so far.

OK, so I have spent the weekend successfully realising that filling and sanding is going to take me forever and a day, longer if I want to get it 'right'. Steaming off the paint seems about the same, with added mess and the risk of blown plaster.

I'm now considering lining paper, which someone described above as "the easy option". The walls are now clean, sanded, no loose flakes but still with patches of paint and bare plaster. How should I best prepare these for lining paper? A coat or two of thinned wallpaper paste? Or should I give it another blinding coat to seal the plaster before the wallpaper paste?
It was built in 1980. The wallpaper I stripped had been up since the house was built (or shortly after).

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