Prepping old bare plaster

[jc2001]

I am in the process of stripping wallpaper done about 20 years ago over the original emulsion finish.

I am finding that in most places the emulsion pulls off too, so much so that I am having to strip it off as well - it's hard work but it does scrape off fairly easily after 20 secs under the steam stripper. So I am now left with bare grey plaster in fairly good condition (it's about 25 years old).

Can anyone suggest how to prep it for painting. Should I treat it like new plaster and apply a mist coat first? My main concern is why the original paint adhered so badly - it has happened elsewhere in the house and I've got another wallpapered room to strip after this.

John

 

[beano1939]

I have used diluted pva sealer in similar situations. This provides a good base for more plaster or Emulsion paint or wallpaper. It is particularly good if you need to spot repair the old plaster before finishing.

 

[jc2001]

Thanks beano1939. I got all the paint off today and the plaster seems in good shape. It wetted ok with the steam so I was planning to try a mist coat as per misterhelpfuls recent general post.

 

[misterhelpful]

The reason it didn't adhere properly in the first place is probably because the mist coat was done incorrectly. (I see you read my post on the subject. )

If you have scraped as much of the loose paint off as you can and it appears sound, you can now apply a mist coat to the bare areas. Once this has been done, it may be necessary to apply some fine surface filler to any proud edges of the old paint to 'feather in' the ridges where it meets the bare plaster. Then, sand it all smooth, apply a mist coat to the filler and you can continue with your painting.

If you find that the remaining paint begins to lift and peel when you mist coat to the bare areas, it may be necessary to apply a coat of Zinsser Gardz (or a similar product) to bind the paint down before continuing. This can be done as a precaution before misting, but may not be necessary. PVA really isn't the way forward.

 

[jc2001]

Thanks MH for the advice. I suspect you are right about the mist coat not being done properly - if at all.

The old paint scraped off quite easily after a steam blast and by last night I managed to get it all off apart from a couple of inches next to the coving where the ceiling paint had been used and a largish patch in the middle of one wall where it looked like some white paint (perhaps the ceiling paint) had been rubbed on with a roller. A bit of filling holes and these edges followed by sanding gave me a nice smooth surface.

And this afternoon I applied a mist coat of thinned Dulux matt emulsion (not vinyl) which seems to have gone on ok. I am hopeful the main coats will go on fine now. One of the walls will be wallpapered and I plan to size this with paste first.

 

[Snacker]

To prepare bare plaster ready for emulsion I'd use a proper plaster sealer like Beeline or one of the Zinsser products. I'd NEVER use PVA as in my experience (and from what many other people have also said) your emulsion won't adhere to it properly and you'll end up with cracking and/or flaking paint.