We're moving some stuff around at work, and there's patches of paint
need touching up.

Someone i'm guessing has painted fresh plaster and not prepared the wall
first,

So while the paint looks OK as it stands, where we are painting, it is
as if the new paint is wetting the old stuff and then the whole lot
wants to come off the wall!

So we scraped the loose off, sized the parts that look like bare
plaster, but as we go back and paint more of the same is happening.

So whats the solution here? It's looking like all the existing paint
needs to come off, the best way of doing this appears to be put ####ing
new paint on it!

Sand it all off?

On 14/05/2020 13:18, R D S wrote:
We're moving some stuff around at work, and there's patches of paint
need touching up.

Someone i'm guessing has painted fresh plaster and not prepared the wall
first,

So while the paint looks OK as it stands, where we are painting, it is
as if the new paint is wetting the old stuff and then the whole lot
wants to come off the wall!

So we scraped the loose off, sized the parts that look like bare
plaster, but as we go back and paint more of the same is happening.

So whats the solution here? It's looking like all the existing paint
needs to come off, the best way of doing this appears to be put ####ing
new paint on it!

Sand it all off?

Old property? Potentially damp wall? Has the plaster been sprayed with
silicone? Does it have to look "good"? If not maybe undercoat with SBA??

On 14/05/2020 13:54, newshound wrote:

Old property? Potentially damp wall? Has the plaster been sprayed with
silicone? Does it have to look "good"? If not maybe undercoat with SBA??

It's an old property but was refurbed a few years ago, beyond that I
don't know. There's no damp.

It doesn't have to look amazing but needs to not look a bag of..... but
i'm not spending 10 quid per litre on acrylic based paint!

I'll get as much off as I can scrape off and attack it with PVA* before
painting, or would lining paper be better?

* Suggested by a decorator in the family, but I thought that was a no-no?

On 14/05/2020 13:18, R D S wrote:
We're moving some stuff around at work, and there's patches of paint
need touching up.

Someone i'm guessing has painted fresh plaster and not prepared the wall
first,

That's what Leonardo /should/ have done, or the Last Supper wouldn't be
such a mess.

--
Max Demian

On 14/05/2020 14:12, R D S wrote:
On 14/05/2020 13:54, newshound wrote:

Old property? Potentially damp wall? Has the plaster been sprayed with
silicone? Does it have to look "good"? If not maybe undercoat with SBA??

It's an old property but was refurbed a few years ago, beyond that I
don't know. There's no damp.

Is the plaster actually plaster or an alkaline lime material. I have had
bother with that in places in my old Victorian building. But it was more
that the paint would cure OK at first and then gradually blister off.

pH test or litmus will show if the surface is strongly alkaline.

It doesn't have to look amazing but needs to not look a bag of..... but
i'm not spending 10 quid per litre on acrylic based paint!

I'll get as much off as I can scrape off and attack it with PVA* before
painting, or would lining paper be better?

* Suggested by a decorator in the family, but I thought that was a no-no?


--
Regards,
Martin Brown

On 14/05/2020 13:18, R D S wrote:
We're moving some stuff around at work, and there's patches of paint
need touching up.

Someone i'm guessing has painted fresh plaster and not prepared the wall
first,

So while the paint looks OK as it stands, where we are painting, it is
as if the new paint is wetting the old stuff and then the whole lot
wants to come off the wall!

So we scraped the loose off, sized the parts that look like bare
plaster, but as we go back and paint more of the same is happening.

So whats the solution here? It's looking like all the existing paint
needs to come off, the best way of doing this appears to be put ####ing
new paint on it!

Sand it all off?
I had a similar problem painting a modern extension. No idea what caused
it (maybe the (crap!) plasterer over-polished the plaster) but the
solution was to spray the problem areas with stain stop and then paint
them normally.

On Thursday, 14 May 2020 14:33:14 UTC+1, Martin Brown wrote:
On 14/05/2020 14:12, R D S wrote:
On 14/05/2020 13:54, newshound wrote:

Old property? Potentially damp wall? Has the plaster been sprayed with
silicone? Does it have to look "good"? If not maybe undercoat with SBA??

It's an old property but was refurbed a few years ago, beyond that I
don't know. There's no damp.

Is the plaster actually plaster or an alkaline lime material. I have had
bother with that in places in my old Victorian building. But it was more
that the paint would cure OK at first and then gradually blister off.

pH test or litmus will show if the surface is strongly alkaline.

It doesn't have to look amazing but needs to not look a bag of..... but
i'm not spending 10 quid per litre on acrylic based paint!

I'll get as much off as I can scrape off and attack it with PVA* before
painting, or would lining paper be better?

* Suggested by a decorator in the family, but I thought that was a no-no?

and red cabbage juice can be used as a pH indicator.

For problem surfaces you can always paint a layer of oil based undercoat on first, solves most problems.


NT

On 15/5/20 9:23 am, wrote:
On Thursday, 14 May 2020 14:33:14 UTC+1, Martin Brown wrote:
On 14/05/2020 14:12, R D S wrote:
On 14/05/2020 13:54, newshound wrote:

Old property? Potentially damp wall? Has the plaster been sprayed with
silicone? Does it have to look "good"? If not maybe undercoat with SBA??

It's an old property but was refurbed a few years ago, beyond that I
don't know. There's no damp.

Is the plaster actually plaster or an alkaline lime material. I have had
bother with that in places in my old Victorian building. But it was more
that the paint would cure OK at first and then gradually blister off.

pH test or litmus will show if the surface is strongly alkaline.

It doesn't have to look amazing but needs to not look a bag of..... but
i'm not spending 10 quid per litre on acrylic based paint!

I'll get as much off as I can scrape off and attack it with PVA* before
painting, or would lining paper be better?

* Suggested by a decorator in the family, but I thought that was a no-no?

and red cabbage juice can be used as a pH indicator.

For problem surfaces you can always paint a layer of oil based undercoat on first, solves most problems.


NT

Or try shelac alcohol base as a first coat then ucoat