The best paint to cover and block a stain

Updated Jan 18, 2024 | Posted Aug 28, 2019 | Professional insight, Product Advice | 15 comments

There are several different types of stain block on the market, each of which has attributes that suit different situations. In this blog, I’ll talk through the best paints to cover and block a stain based on my experience as a Decorator.

 

The Different Types of Stain Block Available

 

I thought I’d begin by taking you trough the different types of stain blocking products available and explain why you might use each of them. Further down the blog, I’ll choose the best stain block for each.

Water-based stain blocks – These tend to be quicker and easier to use than the other options, with less smell. They are more environmentally friendly too. The downside of using a water-based stain block is you may find it less effective on difficult stains such as water marks and grease.

Stain block and emulsion in one – These are innovative products designed to reduce the number of coats of paint needed to cover and block a stain. These can be quite effective, except on very difficult stains.

Oil-based stain blocks – These are probably the most effective stain blocks available, so you might use them on very difficult stains like water-damage and mould. The biggest downside is the smell, which can be quite overpowering in a confined space. Extended drying times can also be an issue.

Shellac Stain Blocks – I like using shellac. It’s too brittle to be used outside, but inside it is as good as any oil-based stain block. You can normally paint over shellac-based stain blocks in 45 minutes too.

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The Best Water-Based Stain Block

 

Each of the main paint manufacturers have their own water-based stain block. These are quite simply labelled “stain block” and are by far the easiest option, however, a lot of them are not very good. The only one I have used that I really rate is the new Zinsser BIN Aqua.

Even though it’s water-based, Zinsser BIN Aqua is genuinely one of the best paints to cover and block a stain. You’ll find it easy to apply, blocks odour, has fantastic opacity, and you can paint over it again after 45 minutes.

I have tested this paint as a stain block extensively on grease, lipstick, red wine, nicotine, coffee, felt tip and water-damage. It isn’t very good on water damage and certain felt tips still bleed through, but for everything else it’s fantastic. I tend to apply two coats of Zinsser BIN Aqua 20 minutes apart, then wait an hour, then paint over with my topcoats. This is a really good product.

The Best Stain block and Finish Coat in One

 

As paint technology advances, “all-in-one” type stain blocks are starting to pop up. As a paint geek, I’m always chomping at the bit to test products like this as soon as they’re launched. There are two products on this section I’d like to talk about: one matt emulsion and one eggshell paint.

 

Johnstone’s StainAway

This is a durable matt emulsion that can also be used as a stain block. The important thing to remember if you’re using this paint is to adhere to the drying times, otherwise it will fail.

It isn’t the best paint to block water stains or other difficult marks, and it can ‘flash’ on large light-critical areas.

However, it works fantastically well on most stains, it’s very easy to use, has fantastic opacity, and you can get it mixed into any colour.

This was the first product of its type on the market. Some Decorators I know use it as a normal emulsion, simply because the opacity is so good. This is the best paint to use for covering light stains such as smoke damage or nicotine over large areas like whole ceilings or walls

Bradite One Can Eggshell

This is the other “all-in-one” product I wanted to mention. Bradite Once Can Eggshell can be used as an adhesion primer, stain block, and a finish coat. You could use it to paint your woodwork, or as an emulsion.

It’s a very good paint for blocking a stain. As with other water-based paints, I wouldn’t use it to tackle water damage or server marks, but it will work in most other cases. It’s very durable too, so perfect for painting a bathroom ceiling.

The Best 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 well ventilated. Otherwise, the fumes are a bit much.

Zinsser Cover Stain

You’ll find Cover Stain easy to use, available in different colours, and very good at blocking stains. The official recoat time is 2 hours, but I tend to dilute it with white spirit, apply two coats in quick succession, then wait 2 or 3 hours before applying my topcoats.

I like using Zinsser Cover Stain for blocking stains and odour. As a Professional Decorator, it’s a product I keep in the van and use often.

Oil-Based Undercoat

Genuinely the best paint to cover and block a stain. If oil-based undercoat doesn’t work, then nothing will. Undercoat is also readily available and cheap as chips.

Undercoat does stink when used over large areas, and you will need to wait 24 hours for it to cure properly before you can paint over with a water-based product. For this reason, I tend to stick to Cover Stain or one of the water-based products unless I’m dealing with a really bad stain.

The Best Shellac 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. It works just as well as oil-based undercoat.

Any shellac-based primer will do a job, but the best I have used is HB42 PS1 (Primer, Sealer, Stain Block). It has better opacity than the others, seems to take less coats, and is easier to use.

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.

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FAQs

 

What is the best stain block for damp stains?

No stain block will stop water from coming into a room, so you need to fix the root of the problem before painting. But even when that’s done, there are not very many products capable of dealing with water stains.

My advice would be to stick with good old-fashioned oil-based undercoat, or a shellac-based primer. Avoid water-based stain blocks for this particular task.

 

How many coats of stain block do you need?

It depends on the nature of your stain and the product you’re using to cover it. One coat of stain block is often enough, but I always apply two anyway. I only do this because there is nothing worse than finishing a room, only to encounter problems further down the line.

 

Can I use PVA as a stain block?

No, you cannot use PVA as a stain block.

 

Will stain block stop mould?

Stain block will prevent the stains caused by mould from bleeding through your ‘finish coat’, but it won’t prevent mould from returning. For that, you may just need an anti-mould paint, or you may need to investigate why the mould is there.

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What do Other Decorators Think is the Best Paint to Cover and Block a Stain?

I do like Zinsser Cover Stain 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 for stains, 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-based paint 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 when people rush the recoat.

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.

Rob Mitchel

If you have the time to wait for your stain block to dry, then oil-based undercoat will beat any fancy Zinsser product.

Kevin Baird

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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

I’d give the stain a good coat of oil-based undercoat. Allow plenty of drying time before giving it a coat of Armstead pure brilliant white emulsion. Again, give it time to dry and see if the stain comes back. If it doesn’t, go ahead and final coat it in your chosen paint. if the stain does come back, source where it’s coming from and solve the issue, then repeat the process to cover the stain.

Stephen Russell

I find that oil-based undercoat is the best paint to cover and block a stain. As a decorator, if I get the job, then I arrange to go round a few times in the evenings to apply multiple coats of undercoat. Then when I start the job, if the stain has come through again, I know that the source of the stain is still active. Maybe the client has water leaking into their house, or maybe there is a different problem that needs sorting before I can paint.

I find that once applied, oil-based undercoat covers well with the first coat of emulsion and then I have total piece of mind before the final coat. Sometimes with Coverstain and shellac I find there is a shiny patch that worries me.

Lee Robinson

Blockade beats Zinsser BIN to block a stain. Great product and easier to apply.

Mandy Penman

I’ve always used Coverstain and it never fails, great stain blocker 👍

John Sweeney

Crown PX4 is the best paint to block and cover a stain…1 hour, job done. No stains will ever get through.

Vaughan Dibble

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Oil-based undercoat usually does the trick when blocking stains is time isn’t an issue. I tend to carry a spray can of polycell stain block for occasional water stains. It’s just easier and it dries in 30mins. Much better than the Zinsser alternative which gets clogging issues after the first use.

Clive Hamilton

Oil based undercoat is the best paint to cover and block a stain for me. Yes, takes longer to dry, but for larger areas it’s a cheaper and more effective than the Zinsser products. Undercoat also doesn’t flash/shine through the emulsion. Pliolite is another good alternative, these products are also great over smoke/nicotine.

Ian Haveron

I always use one Cover Stain then one coat of 123plus on any nasty stains. Only because emulsion will sit on the Cover Stain and take ages to dry.

Matthew James Rees

PS1 for me. It’s a fantastic primer for blocking stains.

Fred Mercer

Just use oil-based undercoat. That’s how we did it years ago and it still works better than any of these water-based stain block products.

Kevin Shortman

Zinsser Cover Stain or B.I.N for stain blocking👍

Dave Molyneux Professional Decorator

Zinsser Cover Stain

Or

Johnstone’s StainAway

Alan Moloney

Updated Jan 18, 2024 | Posted Aug 28, 2019 | 15 comments

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15 Comments

  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.

    Reply
    • Mike Cupit

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

      Reply
      • 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??

        Reply
  2. Casey

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

    Reply
  3. Stuart Hart

    Dear Decorators forum UK,

    The word in UK English is mould.

    Reply
    • Chels

      Gold medal for you!

      Reply
  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.

    Reply
    • Mike Cupit

      Try Johnstone’s Trade StainAway

      Reply
  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.

    Cheers
    Joe

    Reply
  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?

    Reply
  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.

    Reply
  8. D Horn

    New to the market getting great reviews BEDEC ALL PRIME- All Surface. Stains, Rust, Tannins, all surfaces and water based.

    Reply
  9. Jeff King

    Alkaline resisting primer is the best product I have know for covering stains… I’ve been using this for over 30 years

    Reply
  10. Adrian T.

    I have a few stains on my bedroom ceiling which I used to think were water stains so applied 2x coats Zinsser. After a year or two the stains came back. Then, I painted over them with oil based gloss. Stains returned a year later. The ceiling has two layers of plasterboard. (Also had some re-roofing and chimney stack work done twice in 5 years but it came back).
    I stuck a couple of screwdrivers up through the ceiling, left them there whilst I went up into roof space. The plasterboard (covered by loft insulation) in the roof space all around the screwdrivers was bone dry!
    I also have a small 2” diameter patch on a wall at waist height that keeps returning after painting over it.
    Any ideas what the stains are? I’m thinking some type of oil used in the manufacture of the plasterboard. Thanks

    Reply
  11. Adeymcr

    We have used smith and rogers blockade on internal woodwork, to block traces of lead paint in the wood left after stripping using peelaway. Blockade is relatively high in voc content, is there any low voc product we can put on the blockade to reduce vocs in the atmosphere, before applying the top coat of acrylic eggshell?

    Reply

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