orange/red dust on old plaster ?

butterfingers

Hi,

I'm in the process of stripping wallpaper off old (20+ yr) plaster. The plaster
itself seems fine, no cracks or damp etc, but in places there are patches
of an orangey-red powder on the surface of the plaster. It nearly looks
like chalk dust. I'm not sure if its coming from the plaster itself or from
the wallpaper. Anyone seen anything similiar ? As the plaster seems fine
I'm not that worried, but I am curious as to where its coming from.

I'm planning to paint the walls after I've stripped them. As this is oldish
plaster is there anything special I need to do to prepare them ?

Thanks all,

Butters.

backboiler

My house is just over 50 years old and the plaster sounds similar. After stripping the wallpaper, I gave the walls a light sanding and then a coat of polybond (5:1, water : pva). That salmony coloured dust goes everywhere though so cover up furniture and your bodily breathing openings.

butterfingers

Thanks backboiler, I'll give that a go. You didn't have any problems then
later with painting over the polybond ? People seem to be really
divided over whether its best to use diluted matt coat first instead of
the polybond.

Thanks,

butters.

backboiler

No, no problems at all. Wall just slurped it up. Just don't make the mix too glue-heavy.

butterfingers

Great, thanks a lot.

Butters.