Paint staining problem

[regsmyth]

I wonder if anyone can help me understand and solve this problem I have.

I have stripped out the room, removed the wall plasterboard and fitted kingspan between the studs.
I used polythene behind the plasterboard and skimmed it all.

The room was unheated but ventilated during the works and while decorating.

I even painted onto the bare plaster over the window beading with an oil based primer.

I used lining paper and a b&q emulsion.

There was no indication of staining on the lining paper, but when I applied the emulsion - well you can see the results. No amount of additional coats has an effect.

I tried a bit of oil based undercoat on a small area, and once dry, found the staining was blocked, but the area of undercoat is visibly different.

I have decorated this way so many times before, this has really caught me out, and as well as not being sure of the best way to resolve this now, I am also looking for an understanding of what caused it.

Anyone help please?I wonder if anyone can help me understand and solve this problem I have.



I have stripped out the room, removed the wall plasterboard and fitted kingspan between the studs.
I used polythene behind the plasterboard and skimmed it all.

The room was unheated but ventilated during the works and while decorating.

I even painted onto the bare plaster over the window beading with an oil based primer.

I used lining paper and a b&q emulsion.

There was no indication of staining on the lining paper, but when I applied the emulsion - well you can see the results. No amount of additional coats has an effect.

I tried a bit of oil based undercoat on a small area, and once dry, found the staining was blocked, but the area of undercoat is visibly different.

I have decorated this way so many times before, this has really caught me out, and as well as not being sure of the best way to resolve this now, I am also looking for an understanding of what caused it.

Anyone help please?

[img]http://i298.photobucket.com/albums/mm273/regsmyth/stains2.jpg

 

[joe-90]

When using oil undercoat as a stain block you need to thin it down. Maybe 10% or more. If you need two coats it dries pretty quick so don't put it on too thick.

As far as what has happened I can only guess because I've not seen it before.

My guess is this:

The staining has appeared over the galvanised clouts and trim.
Galvanising means zinc coating. Zinc + moisture will create zinc oxide. Zinc Oxide is white. The white oxide has combined with the red paint to make lighter spots.

I may be wrong but Professor Dec will be along shortly.

 

[Robbie uk]

Sort of looks like it was painted on wet plaster. I doubt you have done this, but just looks like it. If its thoroughly dry then use some Zinnser Bin on it to seal it and coat it again.

 

[TheDec]

Professor Dec indeed, you cheeky monkey.

Dec

 

[regsmyth]

I think the moisture in the room must have been a factor. The stains are 99% on the external walls of the room, I guess these were colder so attracted more condensation?
Although at the time, it didn't seem like the walls were damp though.

However they did take a long to dry out after plastering - perhaps over a week.

But isn't it a bit crazy that the stain came through the oil based primer, and the lining paper?

So Joe are you suggesting I should thin the undercoat, then do the whole wall with it, before going out and spending another £30 on paint?
I fear if i just go over the stain bits it'll always show.

Is Zinnser bin so much better than an oil undercoat/primer?

I'm going to try a spot of knotting solution, will let you know if it works.

This is such a drag - never had a problem like this before.

 

[joe-90]

I don't think I've seen this fault before so I wouldn't like to say. You'll have to try a test area first.

 

[deanibusmaximus]

On the Zinsser point regsmyth. I swear by Zinsser coverstain as it is easier to use and cheaper than Zinsser bin. It still dries fairly quick.

Like Joe, I would suggest a test area first rather than go straight in with recoating the whole room.

As a side point, I run a dehumidifier 24/7 at home, and I take one to my jobs with me at this time of year. It really helps to stop moisture from interfering with my work. At home it does not cost me the earth because it switches itself on and off as it maintains the desired setting.

dean

 

[joe-90]

 

[dcdec]

Pigment in paint can change colour or become lighter when applied to chemically active substrates. I think thats your problem, it could be the primer you used on the beading etc or some sort of chemical contamination from the materials. I think the only way you'll get to the bottom of it would be to send a sample to the paint company and they may be able to identify something in the paint that shouldn't be there.

Check that the beading you used was galvanised and if it could have come into contact with any chemicals during storage/transportation, you said you bought the paint from B&Q, my local store often has materials sitting out in cold wet weather in their yard and the packaging is often damaged and ripped so again this could be a source of potential contamination.

I'd agree with the coverstain comment to try to seal/block the problem but it would be nice to know the root of the cause as i've not seen this before either. Its got nothing to do with drying time thats for sure

 

[regsmyth]

Ok well thanks for the tips. I used knotting solution over the stained areas and it covered pretty well with the emulsion. You can see a very slight patchiness to the uniformity of the colour, but only if you look really hard.

I think it must have been excessive humidity that prevented the plaster from drying out normally. I wasn't aware that galv and damp would produce zinc oxide, but it makes sense.

The photo shows the left side of the reveal treated with knotting and repainted with emulsion. I am just starting to apply knotting along the top edge, to cover the undercoated area which is visible through the emulsion.

[/img]

 

[opps]

For what it's worth both, BIN is basically knotting solution with pigment. Both are shellac based and cleanable with household ammonia.

 

[RonnySanders]

Hi dedec! I agree with you that the problem is only pigment in paint that can change color or become lighter when applied to chemically active substrates. Thanks for providing your informative post.

 

[opps]

Why do spammers such as Ronnie think that no one will notice that they are just copy'n'pasting previous answers???

Go away, muppet...