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The best paint to cover and block a stain

Updated Nov 9, 2022 | Posted Aug 28, 2019 | Product Advice, Professional insight | 11 comments


The best paint to cover and block a stain


There are several different stain blocking products on the market which are all good in a different ways, or for blocking and covering up different types of stain. I’ll take you through the main paints in this article, which will help you make the right choice. You can research each product on the Decorators Forum UK.


Generic Waterbased stain blocks


Each of the main paint manufacturers have their own water-based version of stain block. These are quite simply labeled “stain block” and are by far the easiest option, however, may not be as effective on harder stains. This doesn’t mean they don’t have their uses; a ceiling which is affected by nicotine from cigarette smoke for example. Just don’t expect miracles, any heavy stains need to be dealt with by something a bit more robust.


Stain block and Finish Coat in One


As paint technology is advancing, we now have all these new “all-in-one” products that are really quite impressive. Johnstone’s StainAway is a white, durable matt emulsion which blocks out stains quite affectively and leaves a nice finish, eliminating the need for more than one product. This product works well on pretty much any type of stain, except maybe water marks. It is important to leave the first coat for at least 4 hours before applying your second.

Another fine example of this is Zinsser Perma White. Again, it will block out mild stains, doubles up as an emulsion and has mold inhibitors, meaning it will combat mould and mildew growth in the future. It is the perfect product for a bathroom or kitchen.

The other advantage is Zinsser Perma White is durable enough to use on ceilings, walls and woodwork and it can also be tinted. Note, this product will not block a stain as effectively as some of the products listed below, but if you want longevity in a room susceptible to mold growth then this is the product for you.


Oil-Based Stain Blocks


Now we are talking!! These products are the most effective at blocking and covering stains such as grease, water marks, heavy nicotine and graffiti. Just make sure if you are applying it inside over a large area, you keep your work area nice and ventilated. Otherwise the fumes are a bit much. Look out for Zinsser CoverStain, or any oil-based undercoat. I personally feel these work very well. You can buy coverstain from loads of trade outlets but unless you have a trade account it may be better to purchase it online.


Shellac Based Stain Block


Shellac is a material made by beetles and used in both nail varnish and paint The beauty of using shellac-based primers to block a stain is the effectiveness and speed of which the product dries. There is probably no paint more capable than shellac to block any stain.


The best product of this type I have used is HB42 Primer Sealer, which is available online. You’ll find the opacity and ease of use better than most other shellac-based products. It will hold any type of stain back, and you can paint over it after around 40 minutes. Unlike other shellac, or oil-based primers, there is very little smell from it.


You will have problems washing your tools out afterwards, so I suggest using cheap painting equipment, then throwing it away after use. This product is for interior use only.

What do Other Decorators Think?

I do like coverstain in a spray can for small areas. I’ve always got one in the van in case I have any stain bleeds. Shellac is good for larger stains like whole ceilings. Nothing is better than oil-based undercoat, but it can’t be healthy because of the fumes.

Ryan Micheal Foulger

The cheapest and best way to cover and block a stain has always been oil-based undercoat. All you need to do is loosen up the product with some white spirit, double roll, leave to cure and you’re good to go. Shellac is good, but it can lead to adhesion issues between stain block an emulsion if you’re not careful. You can’t use contract matt emulsion if you want to paint over shellac.

Mike Farrington

If drying time is an issue then use Zinsser BIN, however often it dries as an amber colour. If drying time isn’t an issue and you never want a call back for a stain then use oil undercoat, any will do. Never fails and dries white. Coo-Var also has a good product which is a stain block and finish in one. Perfect for a small ceiling. Johnstone’s Stainaway is good, however I have seen it fail a few times in other people’s experiences.

Jamie Wakeford

In my opinion, The best paint to cover and block a stain is oil-based undercoat. It’s just a shame about the drying time and paint fumes. PS1 primer is a great alternative, dries quick and doesn’t stink. That’s all I use now.

Sean Danes - The best paint to cover and block a stain

Depends on want the stain is. For water mark or if just a small stain normal use bin as well hold it back quick drying time. For large water stain again a Zinsser product, coverstain primer sealer .

Alan Shorney

Smith and Rodger blockade for me. It’s like Zinsser BIN but better. I haven’t tried PS1 yet.

Stooie Walker - the best paint to block and cover a stain

Of you have the time, oil undercoat will beat any fancy Zinsser product when it comes to stains.

Kevin Baird

Back in the day we used to use pliolite masonry paint to block a stain, but thinking back, I’ve no idea how we put up with the fumes!! It is horrible inside!! Absolutely kills stains though. Same with oil-based undercoat really, but that is still a good option.


Johnstone’s StainAway is a good product providing you leave a good 5 hours in between coats. For large areas I’ll either use Zinsser Coverstain or the PS1 Primer, which is also good.

Mike Johnstone

Why fix something that isn’t broke?? We have been using oil-based undercoat to block stains for years and it is still the best paint for the job. It is cheap, you can dilute it and it blocks stains better than anything else on the market.


Just loosen the paint a little with white spirits, then double roll. Providing there isn’t an active water leak, it will work every time. You need to let undercoat dry over-night before you paint over it.

John Jones

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Updated Nov 9, 2022 | Posted Aug 28, 2019 | 11 comments

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  1. Ms Doreen Elcox

    There are shiny caulking stains (the caulking was used to stick down paper edges) on newly painted, papered walls. The paint is dark mustard-coloured emulsion. Further coats of paint have not covered them.
    Can you recommend a cover that I can just paint over.

    • Mike Cupit

      You could use coverstain, oil-based undercoat or zinsser bin

      • Tracey Sharp

        I’ve got a job to do – I am not a professional – part of the ceiling and walls have soot stains from a previous fire. I know that not matter how I clean this it will leach through the emulsion – what’s the best stain block to use please??

  2. Casey

    What is the best Stain block for soot after fire damage…ceilings mainly

  3. Stuart Hart

    Dear Decorators forum UK,

    The word in UK English is mould.

    • Chels

      Gold medal for you!

  4. Sandra

    i would like to find a stain block that doesn’t have a strong smell and suitable for use in homes with people sensitive to smells or have breathing problems.

    • Mike Cupit

      Try Johnstone’s Trade StainAway

  5. Joe

    Hi all

    Just wondering you could help is there any type of paint or type of pva that will work over water repellent.


  6. Ellie D

    Hi, We have a few persistent spots in our bathrooms where condensation keeps coming through. What’s the best produce to use to stop it being visible and is it as easy as painting on top of what’s there or is there prep work in the areas needed first?

  7. John Rose

    Jow many professional decorators go back and look at their work after a few years. A couple of coats of a hood oil based white gloss…plenty of opacity and good film forming properties impervious to water based stain bleed always works for me.


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