Getting rid of Watermarks

[Exige77]

Looking for help with a painting question.

I know if you get watermarks in an Emulsioned ceiling etc they are difficult to remove. You can paint it endlessly and they still come through.

If you paint over the marks with oils based paint and then paint again with emulsion they dissapear.

My question is, why do they keep re-appearing when you emusion over them ?

Thanks

Ex77

[shirt]

no idea, but you can buy a small tin of barrier paint to use as a basecoat, works a charm. only point to watch is tht you can't sand it after application else it peels off as one piece of film.

[cinque]

Exige77 said:

Looking for help with a painting question.

I know if you get watermarks in an Emulsioned ceiling etc they are difficult to remove. You can paint it endlessly and they still come through.

If you paint over the marks with oils based paint and then paint again with emulsion they dissapear.

My question is, why do they keep re-appearing when you emusion over them ?

Thanks

Ex77

Emulsion is water based, therefore water will penetrate and mark.

To prevent water marks, decorators use bog standard oil based paint to base coat / cover the marks and then emulsion over the top, therefore creating an oil barrier. This is how decorators stop damp/condensation etc coming through.

I'd be more inclined to find out why you have water marks on the ceiling i.e. leak from roof or floor above and fix that first before you go prepping and finishing a ceiling.

[Simpo Two]

cinque said:

Emulsion is water based, therefore water will penetrate and mark.

Agreed, but if the water has now all gone leaving just the stain, I can't think why it would come through successive coats.

It's rather like knots coming through gloss paint on architraves, only in reverse

[cinque]

Simpo Two said:

cinque said:

Emulsion is water based, therefore water will penetrate and mark.

Agreed, but if the water has now all gone leaving just the stain, I can't think why it would come through successive coats.

It's rather like knots coming through gloss paint on architraves, only in reverse

What you got above the ceiling ?

[rsstman]

cinque said:

Simpo Two said:

cinque said:

Emulsion is water based, therefore water will penetrate and mark.

Agreed, but if the water has now all gone leaving just the stain, I can't think why it would come through successive coats.

It's rather like knots coming through gloss paint on architraves, only in reverse

What you got above the ceiling ?

dont think that matters as long as he has stopped the source of the water, but it is very strange how these completely dry staines come through the emulsion, i suppose it just gets re-wetted by the emulsion and mixes into it.

[jas xjr]

the op is correct.even if you rectify the cause of the stain and dry it out,the stain will appear through the new paint.

[B17NNS]

One of life's great mysteries to which I have no answer.

However as has been said, a coat of oil based undercoat or a spray of 'stain stop' topped of with your emulsion of choice should deal with the pesky blighter.

[cinque]

Not if you put an oil based paint up there first it wont


1. Sort out any probs with regards to leaks/drips/bathrooms/piping etc These can come from the most unlikely sources. you'd be surprised.

2. let the ceiling dry out pref. with a humidifier in the room.

3. Once dry prep. the surface base coat with an oil based paint (trade names like stainblock etc are only oil based paint, some with mould inhibitors).

4. top coat with water based emulsion IT WILL NOT COME THROUGH

The only reason the water marks will come through, is if the source of the problem hasnt been rectified, it hasnt dried out properly, the moisture is still present in the wall, or you havent used an oil based paint as a barrier.

Edited by cinque on Monday 18th May 17:02

[rsstman]

cinque said:

2. let the ceiling dry out pref. with a humidifier in the room.

is the a machine to spray humidity around the room or did you mean a dehumidifier?

[Exige77]

The original water mark was from a long since repaired leaking roof.

Been bone dry for more than 5 years.

Just curious why the waterstain, even though now no water present, still comes through.

Reading the above posts maybe the waterstained surface is some how different and absorbs th water from the emulsion in some way thus creating a new water stain each time.

One of lifes mysteries.

Thanks

Ex77

[rsstman]

Exige77 said:

The original water mark was from a long since repaired leaking roof.

Been bone dry for more than 5 years.

Just curious why the waterstain, even though now no water present, still comes through.

Reading the above posts maybe the waterstained surface is some how different and absorbs th water from the emulsion in some way thus creating a new water stain each time.

One of lifes mysteries.
Ex77

thats all i can think that does it.

[Exige77]

Just had a chat with our Chemist at work. Once a surface has been wet and dried this treatment acts as a kind of surficant. When this surface is wetted again the previously wet area wicks better than the previosly dry area. Moisturwe is then absorbed into the old water mark from the new paint and will take longer to dry than the normal surface thus creating another water watermark.

Now let's get onto Climate change, world hunger, why people buy Prius's etc.

Ex77

[Simpo Two]

Exige77 said:

Once a surface has been wet and dried this treatment acts as a kind of surficant

Surfactant, or wetting agent. Good answer though

[cinque]

rsstman said:

cinque said:

2. let the ceiling dry out pref. with a humidifier in the room.

is the a machine to spray humidity around the room or did you mean a dehumidifier?

[Exige77]

Yes Surfactant and not surficant ?? Spelling is not my strongest point. My Daughter has her English GCSE today. Hope her spelling is better than mine!!

Ex77