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Stain Blockers

At some point in time you’re going to come across the common problem of a stained surface, be it from damp, nicotine or any number of causes, on walls and ceilings.

As you’ll find, simply painting over the stain doesn’t always work as the solvents in the paint you’re using cause the stain to migrate through to the surface. The result being that no matter how many coats you apply the stain still comes through.

The reason for this is actually quite simple – some stains are water-based and some are solvent-based, the same as paint. So if you use a water-based paint on a water-based it’s going to keep coming through. The same applies to top solvent based paints and stains.

The solution, therefore, is to use a different based paint to the stain you’re trying to cover.

So for waterborne stains and nicotine a solvent based (oil-based) paint will usually seal it. And for solvent-based stains such as crayon marks, pen marks, etc a water-based paint will usually do the trick.

And, if you’re not sure what the stain is – a spirit of shellac based primer can often be the answer since it will not allow either to migrate.

Just to complicate matters, because of the move towards eco-friendly water-based paints you will find a lot of general-purpose products which are water based. Although effective against oil-based stains they can be less so with water-satins and nicotine – so only use these if the problem is minor.

You’ll find all manner of different solutions labelled as ‘stain-blocker’ but below are the most popular for every situation…

Stain Stop Aerosol
Polycell Stain Stop Aerosol
(Available from amazon.co.uk)
Ideal for small areas.
Quick-drying, spirit-based aerosol so blocks most stains.
Dulux Stain Blocker
Dulux Trade Stain Block Primer
Water-based for large areas.
A general-purpose primer for walls and ceilings. Can be used to some effect on water and nicotine stains but not ideal. Only use where the problem is minor.
Bulls Eye 123 Primer
123 Bulls Eye
(Available from amazon.co.uk)
Universal water-based primer/stain blocker.
Will work on a variety of stains but, again, for water-based stains like damp and nicotine use only where the problem is minor.
BIN primer
Zinsser B-i-n Primer & Sealer
(Available from amazon.co.uk)
Shellac, spirit-based primer/sealer
Ideal for covering water-based stains in small areas.
Alkali-resisting primer
Alkali-Resisting Primer
(Available from amazon.co.uk)
Not a stain-blocker specifically but a good oil-based sealer for large areas.
Use on walls and ceilings where there is heavy staining from water-damage, nicotine staining, etc

Please bear in mind that when using spirit or oil-based sealers, it is essential you ensure the room is well ventilated during application and for a few days afterwards – particularly when treating large areas.

If you have any questions about which stain blocker to use please get in touch via the contact page.


18 thoughts on “Stain Blockers”

  1. Hi I managed to get some wd40 spray on my emulsion and although tried to remove its still there and looks like water. What can I do so I can then emulsion paint over please

  2. I had a solid fuel Rayburn removed – the chimney off the Rayburn was filled in, sealed and the back wall replastered. An air vent was fitted behind and a cowl was put on the top of the chimney. Unfortunately they did not check the top of the chimney and rain water got in through a small crack in the rendering and the water leached through causing a stain on the replastered interior wall.. That has been repaired and the inside of the chimney is now dry as is the interior wall. The stain keeps bleeding through. I have tried a couple of blockers but the stain keeps coming back. Do you have any suggestions please ?

    • Some stain blockers are water based nowadays and, although they are generally OK, they do not provide adequate defence against very stubborn staining such as you describe.

      First, ensure the chimney and plaster coating is thoroughly dried out. Then apply one or two coats of a solvent based stain blocker.

      The aerosol types (such as Polycell Stain Stop via amazon.co.uk) are often spirit based which is fine. Zinsser B-i-n Primer & Sealer via amazon.co.uk is shellac based and, again, suitable for the situation above.

      The aerosol is ideal for small areas.

  3. We have an issue with staining on a ceiling from tar from an old leaky chimney. The chimney is now sealed off but we think the old plasterboard is leaching through the tar. Will a stain block work and which one? Thanks

    • With tar/bitumen stains a water-based primer such as Zinsser 123 via amazon.co.uk will be effective. A couple of coats, covering at least twice the area affected should do the trick.

  4. I had my kitchen re plastered then a storm took the roof off! A lot of water came through staining the new plaster. Whats the best stain blocker to use? Also would i put the stain blocker directly on the plaster or mist coat it first the block? Thanks!

    • Firstly, ensure the plaster has had ample time to dry out before you do anything. Depending on the type of wall and finish this could take several weeks so the longer you leave it the better.

      I would recommend you apply a mist coat as normal to seal the surface and this will show where the staining is likely to occur. For small patches an aerosol type stain blocker will be easier and most effective.

      For large areas you have an added problem that some brush/roller applied stain blockers these days are water-based and not always 100% effective. You will never really know until after the fact though so it can be an expensive endeavour. For this reason I would suggest a solvent based option such as Zinsser Cover Stain via amazon.co.uk

  5. Hi I have used stain block on my ceiling to block out some water based stains what would be the next best paint product to use as a final coat

    • After the satin black has dried you should use the original finish you intended to use. After the first coat, wait a while to make sure no more stain is coming through and then finish with a second coat.

      It is possible you’ll get a decent finish with your first coat but it depends on the change of colour and type of surface.

  6. I’m using emulsion on lining paper and am left with odd patches which can be seen when looking along the wall. I think this may be due to wallpaper adhesive which hasn’t been removed from the surface when the wallpaper was hung, or maybe a reaction to filler used in the wall (although sealed with BIN). The patches remain after two coats of emulsion. What should I use to get rid of them please?

      • Thanks Darren. The patches are varying in size from small lines to larger rectangles a few inches wide/long. Some have more defined edges than others, which are more wispy. They seem to reflect the light more than the rest of the wall and appear to be a flatter texture. Very difficult to explain. Can I send photos? The patches are white, but a different white to the rest of the wall. I’m using slightly off white paint (Little Greene Shirting intelligent matt).

      • It’s one of two things.

        1)Staining on the original surface which is bleeding through subsequent coats. You can mitigate this by using an oil-based primer to block the stains because the pigment won’t be soluble in a solvent based medium. For small areas the aerosol version of ‘Stain Block’ should work (avoid the the tinned version though as this is water-based and may not work).

        2)You have an irregular surface which is reflecting light in a different way to rest of the wall. This can be difficult to eliminate without resorting to a textured relief finish that twill break up the light.

  7. Hi, I’ve got a small leak in my conservatory which leaks down and damages the paint on the plastered walls. I’ve tried to seal this numerous times but to no avail. Because of this every winter I get some mould and water stains. Is there any paint I can use that will not show up mould and water stains when the inevitable happens every winter? Thanks in advance.

  8. I have washed the ceiling down, but the nicotine still bleeds through what do you recommend? thank you

    • Nicotine will migrate through water-based finishes and, usually, the only way to block it is with a solvent based primer such as Leyland Alkali Resisting Wall Primer or Dulux Alkali Resisting Primer.

      Water-based stain blockers such as Zinsser Bulls Eye 1-2-3 via amazon.co.uk can be effective where the staining is minor but you run the risk of wasting time and money if it doesn’t work.

      When using a solvent based sealer, ensure good ventilation whilst painting and for at least 48 hours afterwards. Once dry, just paint over with the finish of your choice.

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