On Sun, 03 Apr 2011 01:01:43 +0100, Tim Watts wrote:

wrote:


Thank you. My only problem is identifying what is "loose". Nothing is
obviously lifting. I was planning on using PVA to seal the plaster
incidentally but will certainly look into this SBR.


Running over with a steel (regular) wire brush will probably show you - also
an advantage as it will score the paint and give the adhesive some extra
mechanical keying.

So far I have tried a combination of sanding and scraping using an
Aldi palm sander. This removes the paint extreemely slowly. I have
tried a chemical paint remover and oddly enough in small quantities it
actually improves the paint / plaster bond to a remarkable degree. [I
am loath to paint the entire wall with with it though as it probably
has drawbacks as a bonding agent]. Used in standard bubble and scrape
quantities, it is fine, but far too expensive for an entire room.

I didn't think chemical strippers worked on water based paints, and
was a little dubious when I read the label [Some blue gel type stuff].
It works though but in exactly the same way as Nitromoors. i.e very
effective, but dashed expensive if you want to keep the physical
labour to a minimum.

I think I'll go for a bigger sander. Screwfix advertise an Erbaur or
similar that takes 1/3 sheets, and the correct sanding sheets are
available, unlike the Aldi device which seems to require some kind of
sheet that is not generally available within this solar system.

I think the wire brush stands more chance - for tiling, a roughed up (even
badly) surface is a good thing (TM).

I suppose this SBR doesn't penetrate through to the plaster/ paint
interface? I have assumed anything laid on top of the paint [ Which
if it is still on the wall is of an uncertain bond strength] would not
penetrate and reinforce the overall bond. Obviously my blue gel paint
remover must penetrate to the bond and indeed reinforce it, so would
you think that this SBR might do the same?

SBR has very good penetrating powers if the surface is not waterproof. IIRC
the BAL instructions were to dilute it 1:1 with water which makes it
thinner. You need to saturate the surface in one go as it cures fairly
quickly and then becomes waterproof limiting the penetration of any further
applications.

The one thing it does not do is gap fill - so it won't help paint that is
loose with a gap behind (even a tiny gap). But if the paint is stuck on,
even if it - or the surface of the plaster underneath - is weak, it should
make it most of the way through the skim coat of plaster and it will be
noticebly more solid when dried. If any of the surface was fiable, it won't
be afterwards. It is unlikely to help if the skim coat os loose though - you
should tap the wall and sound it out and deal with any serious bits in the
usual way.

One warning though - if spilt on any good finishes, eg floor tiles, bath,
etc, wipe up immediately with plenty of water and a cloth - I have still got
a layer of SBR on my stainless bowl I use for mixing various liquids and
even wire wool won't shift it except in conjunction with white spirit.

It's difficult to guarantee success without seeing your wall, but if you do
a test area, leave a day, then take a scraper and a wire brish to it it
should be obvious if it has had the desired effect. But based on what you've
said and the relative amount of work to try to strip the paint or knock the
skim off and replaster, it would be the first thing I'd try.

Cheers

Tim

Thanks Tim,
Actually this paint seems fairly waterproof. I tried
spraying a mist from a Hozelock bottle but it had little effect
penetration wise.

I have tried a wire brush ( a cup attatchment for my drill), it seems
to effect a slight improvement in some patches. If I turn the drill on
I get grooves.

The surface of the paint is quite resillient, the only weak bit is the
bond between plaster and paint.

My current plan thanks in part to this NG is a matrix of steel blades
to groove the paint, followed by a good scrubbing with a Screwfix
sander [if in stock].


Come to think of it I'll pick up a wire brush tomorrow, maybe a wire
cup attachment isn't the best for scrubbing walls.




HN