Stain Blockers

Zinnser will block the stain coming through, for now, but it won’t cure the problem. You’ll need to remove the mould with a fungicidal solution and allow the wall to dry out in depth otherwise the moisture will just show up some place else.

I am not familiar with Wickes Stain Block but my first thoughts were that it is likely a water based product and, as a consequence, will have a limited effect on water based stains. It does say on the site that it is solvent based though.

The link to the product data sheet, however, is for another product entirely, so not much help there.

It could also just be the case that you need to give the area another coat or two to cover the difference in colour? Hard to say without being there.

Another coat of the stain block you have might do the trick but, if not, I suggest trying a spirit based stain blocker such as Polycell aerosol stain block or, alternatively, a traditional oil-based white undercoat.

I recently had my utility ceiling skimmed, it had previously been patched after my toilet leaked and caused some damage.

Prior to painting I had a decorator out for a quote and he advised me to use a stain blocker prior to painting the ceiling as otherwise the stain would show through.

I used everbuild stain block aerosol and have now done 2 coats of emulsion but can see a sort of dark patch from what I think is the stain block rather than the water damage. Basically where do I go from here? Tia

Water stains tend to be light brown in colour so it is indeed likely the stain block that is showing through. You can get this when using different kinds of paint and usually a couple of extra coats will do the trick.

Do two coats just over the affected area to ensure it is covered and then do one final coat over the whole ceiling to finish.

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.

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? Gavin

You don’t say what kind of finish you want Gavin but, generally speaking, an oil-based alternative would be an easy solution provided you wipe off any moisture fairly regularly. Traditional eggshell or flat oil finish ideally. Alternatively, a mould-resistant finish such as Zinsser Perma White may mitigate the mould issue.

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? Catherine

Please explain these patches in greater detail Catherine. What colour are they and is the shape uniform?

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.

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.

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

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

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? Pete

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

I had a solid fuel Rayburn removed – the chimney off the Rayburn was filled in, sealed and the back wall re-plastered. 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 re-plastered 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? Wendy

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.

I’ve recently wallpapered a ceiling. There was a water leak in the ceiling years ago. The source of the water leak has been fixed, but there is some yellow staining visible on the surface of the wallpaper caused by the leak.

I’m not sure if the staining would be considered as a heavy stain or not, but it is clearly visible in the day during sunlight. block spray?

And would it be possible just to cover the stained area of the ceiling wallpaper or will the entire ceiling need painting after applying stain block on the stained area? Steve

An oil or spirit based stain blocker will usually be effective for a water-based stain. The aerosol-types tend to be spirit based so that may be your best bet. You only need to go slightly over the edge of the stain, not the whole ceiling.

Whether the entire ceiling needs repainting will depend on the colour and finish. A white matt finish, for example, can usually be touched-up quite effectively whilst some colours will be difficult to match exactly and painting a small area may stand out too much, necessitating a full repaint.

Try a spirit-based stain blocker such as Zinsser Cover-Up [amazon link]