Paint Stains

Paint stains can be frustrating to deal with if you don’t understand the cause. The natural inclination is to add another coat but this often doesn’t work and can be a huge waste of time an money.

Most stains occur when a surface is contaminated with something which is water soluble. This contaminant, on contact with a water-based paint paint, work its way through to the surface and be just as prominent as it was before.

The solution is to cover the satin with an oil or solvent-based primer or stain blocker.

In some cases you can also get solvent soluble stain where the same effect occurs. For these, you’ll need to use a water-based primer to block the satin.

Then, there is annoying third kind of stain where neither of the above options work you’ll need to use a shellac-based primer which will work in most cases.

Here are a few problems that people have encountered…

I have read u shouldn’t paint sandstone mullions. Mine were painted and rust is coming through. Should i leave to breathe or have repainted? READ MORE…

It’s common for stone mullions to be painted and small deposits of iron below the surface will react with water and cause the rust staining regardless.

If the staining is unsightly then I would advise spot priming with either an oil or spirit based stain blocker, or a general purpose metal primer, and then paint as normal with a water-based masonry paint.

If the staining is widespread then a pliolite-based masonry paint can help.

Cupboard doors, 2 coats of primer/undercoat & 2 coats of satinwood and they still look patchy orange in places… READ MORE

We have pine doors on our wardrobe – about 30 years old! Can’t get anyone to replace them so decided to paint them ourselves. Put 2 coats of primer undercoat on, then 2 top coats of satinwood and they still look patchy orange in places. When I painted the inside of the doors they came out fine! Help – please. I don’t know what to do? Dee

There have been multiple posts regarding similar issues and the solution is always to use a different base of paint to block out the stain. So, if you used a water based paint switch to an oil-based one and visa versa.

The reason it didn’t happen on the inside is very likely because they have not been stained?

I painted a water based varnish on to emulsion to create a stripe, I have painted over the varnish as I don’t want it anymore but the varnish keeps bleeding through any suggestions? READ MORE..

Use an oil-based undercoat to cover the stripe; leave for a week and then emulsion over it. If it’s only a small area you could use a stain-block aerosol which will be easier and you could to paint over it the next day.

The handrail going up my stairs is mahogany and I want to paint it white. I rubbed it down and have given it 2 coats of primer and undercoat but it hasn’t covered very well. READ MORE…

The handrail going up my stairs is mahogany and I want to paint it white. I rubbed it down and have given it 2 coats of primer and undercoat but it hasn’t covered very well. I gave a small area a coat of satinwood but it was very streaky and in fact looked awful so I wiped it off with a damp cloth but it all came off – undercoat as well. Please advise, Heather

Sounds like the mahogany stain is migrating via the primer and undercoat? If you used oil-based paints then switch to water based and if you used water-based then switch to oil; the stain will be one or the other.

Just to complicate matters, if you have used oil-based and now need to use water-based you’ll find it doesn’t adhere very well to oil based paints that have recently been applied. If this is the case you’ll need to leave it a couple of weeks for the paint to fully cure.

If you need to sue an oil-based finish it’s ok to use 2 coats of water-based primer/undercoat just to kill the staining first.

I need to paint some MDF and Softwood which after it was put in place was contaminated with dog urine. What Primer should I use. READ MORE…

I think the best option would be a standard oil-based wood primer which will seal the surface and prevent any possible staining? With MDF especially, you will probably need to give 2 coats (both thinned 10% with white spirit).

Use an oil-based undercoat and top coat to finish. If you want to use a water-based finish I’d suggest waiting a week to allow the primer to fully cure before application.

I have sanded down my hardwood door gave it 2 coats of undercoat, 2 coats of Dulux Low Sheen Eggshell and the next day yellowing started to come through... READ MORE…

Hi, I have sanded down my hardwood door gave it 2 coats of undercoat, 2 coats of Dulux Low Sheen Eggshell and the next day yellowing started to come through, so next day i gave it another coat and the same thing again and next day gave it another coat and after 4 coats of eggshell the yellowing is still coming through. Please can you advise, thank you, Kind regard, Robert

As a general rule, a stain that migrates (or bleeds) its way through a water-based paint can be blocked with an oil-based paint. As you’ve found, using multiple coats of the same coating just doesn’t work.

You don’t say which yours is but if you are switching from oil to water you’ll need to let the surface fully cure (this can take a couple of weeks) and then lightly rub-down before applying the next coat. An acrylic primer/undercoat is usually the best option and you might want to give it two coats just to make sure.

There are proprietary ‘stain-blockers’ available but are not really suitable in this situation since you’ll need to cover the whole door.

Painted ceiling brilliant white matt emulsion, but it’s come out patchy yellow… READ MORE…

I am currently redecorating a bedroom in my house. The ceiling was painted white, I’ve repainted it white to refresh it, but it’s gone really patchy yellow and white, all over, partly in line with the direction I was rolling it. I have a photo if that would help.

Above the ceiling is the roof space, just insulation above it. The ceiling is the original 1930’s lath and plaster, it’s been papered at some point and painted white. I was painting white on top of this. I was using a pretty standard pure brilliant white matt emulsion, but it’s come out patchy yellow. To a lesser extent it’s also done the same on the top of the wall above the picture rail, also papered and white.

Any advice on how to get it white all over appreciated! Georgina

It’s a fairly common problem Georgina. Usually it’s where there has been a problem with damp.

In both cases you can usually stop the stains from coming through by using a stain blocking primer, such as Polycell Stain Stop, or some white oil-based undercoat first. This will often be enough to prevent any further discoloration through subsequent coats of paint.

In severe case, where stain-blocking doesn’t work, it can indicate an ongoing damp problem that will need to be addressed. It could be water getting into the roof through a broken tile or can be just a build-up of condensation which happens a lot when loft insulation hasn’t been fitted correctly.

However, since you don’t mention any other problems, I think it’s worth trying a coat of Stain Stop on the affected areas. Allow to dry and then paint as normal.

I should point out that there are two kinds of stain block on the market at the moment. I recommend the aerosol type since it is spirit based, dries quicker and tends to more effective even though it can be a bit smelly.

The other type is water-based which means you can apply with a brush or a roller and there is a lesser odour problem. It doesn’t work as well though, particularly with water-based stains (for obvious reasons) so I’d avoid this type if you can.

Stone window sills painted with Sandtex masonry. After a week it blistered and yellow stains came through… READ MORE…

We burnt off the old paint on the window sills back to the stone. We used dulux stabiliser then painted with Sandtex masonry. After a week it blistered and yellow stains came through.

This didn’t happen on the door way areas, lintels or mullions. So we rubbed it down and tried again. The yellow stains are worse now. What have we done wrong? We would appreciate any advice on how to fix this. Max

The sills will have absorbed moisture over the years and this is likely the source of the problem. Even though they were painted before, water will have penetrated via hairline cracks and around the margins. Capillary action does the rest, drawing moisture deep below the surface.

The fact the paint is literally bubbling off so soon suggests a high degree of moisture that needs to escape naturally and this isn’t exactly the best time of year for that to happen either.

I would leave the sills for now and, in the Spring, scrape off as much paint as you can and then leave through the summer for the sills to have a chance to dry out. If they can be covered in some way to protect from further rainfall, all the better.

Our recently painted chimney shows up with streaks after using the log burner. Any advice/recommendations on how to solve this? READ MORE…

As you describe it, the obvious answer is smoke contamination from the burning logs. Not sure how that could be solved to be honest?

I have a few water marks showing through from a leak in the ceiling, would you paint the entire ceiling with the blocker or just the impacted area? READ MORE…

Just beyond the affected area, no need to go further.

See Also
Painting over a stained surface
Stain Blockers
Damp wall at window reveal causing staining and blistering of paint covering
Damp Problems