Water-based paints for woodwork have grown enormously in popularity in recent years, for a number of reasons:
- There have been huge improvements in their quality
- They are non-yellowing, so whites stay looking good for longer
- They have quicker drying times than oil-based products, and are lower odour
- Environmental issues – much lower VOC level than oil-based
- Brushes can be cleaned in water rather than white spirit
But given that the majority of existing woodwork in Britain’s houses would have historically been painted with oil-based paint, we need to ask ourselves, can you use water-based paint over the top of oil-based paint?
How Can You Tell If Existing Paint Is Oil-Based?
The first question to answer though is whether the existing paint is oil-based or water-based. Fortunately, there’s an easy trick to find out the answer, and as with most things decorating related, it involves alcohol! Simply pour a little methylated spirits (or rubbing alcohol, or acetone) onto a cloth and give a patch of the surface that you want to paint a good wipe with it. If some of the existing paint wipes off, it’s water-based; if none of it comes off, it’s oil-based.
Why Does It Matter if You’re Painting Over Oil-Based Paint?
You know the old saying that oil and water don’t mix? Well, it’s true when it comes to paint as well. It all comes down to how well subsequent coats stick to the existing paint. Very few things adhere effectively to oil-based gloss because the surface is so smooth and shiny. So, if your existing paint is oil-based you will need to take a couple of simple but necessary steps to help your new water-based paint stick to it.
How To Paint Over Oil-Based Paint with Water-Based
Step 1 – grease, grime, furniture polish…. None of these are going to help promote great adhesion, so as a first step I’d always clean the surface to remove these contaminants.
Step 2 – abrade the surface with sandpaper (or similar product). The aim is not to remove all the existing paint (assuming that it’s sound, and not chipped or flaking, in which case additional prep would be required). The aim is to take the sheen off the surface, to make it less glossy and therefore easier to adhere to. So, give it a good rub down with a suitable grade sandpaper, and then wipe off the dust with a dusting brush and/or tack cloth.
Step 3 – adhesion primer. These days there is a massive choice of adhesion primers available, and most of them are excellent. These paints are specifically designed to stick to difficult surfaces, and can then be painted over with your choice of finishing paint, while feeling confident that it won’t be chipping or peeling off in the near future.
Most adhesion primers are water-based too, so quick drying and easy clean-up for your brushes.
I’ve used loads over the years, from traditional favourites like Zinsser Bulls-Eye 1-2-3 to recent introductions such as Bedec All Prime (available online by clicker here). Crown Trade PX4 is a bit of a favourite of mine, as is Benjamin Moore Stix; I know a lot of Decorators favour Caparol Haft Primer and Tikurilla Otex Akva. They all do a similar job, and like the abrasion, it’s a step that I wouldn’t risk missing out.
Step 4 – your choice of water-based finish. Again, most manufacturers these days offer water-based finishes, whether it’s gloss, satin or eggshell. Some (such as Johnstone’s and Crown) recommend a coat of their water-based undercoat before applying your topcoat(s), others (such as Benjamin Moore Scuff-X or WRX) simply specify two coats of the finish product, no undercoat. Check and follow the instructions for your chosen system, and as long as you’ve followed the steps above, you should be fine.
So yes, in summary you can use water-based paint over oil-based paint, as long as you follow the process. But then, in the days before water-based paints, you wouldn’t have painted gloss straight on top of gloss – you would always have given it a good “key” and a coat of undercoat first. It’s the same kind of idea – follow the right steps and you’ll get the right result!
The Best Water-Based Paints
Benjamin Moore Scuff X
This is probably the best water-based paint on the market, and you don’t need a primer when painting over oil-based paint. It is expensive, but it’s a case of ‘you get what you pay for’ sometimes. Awesome to use, goes for miles, great opacity and looks fantastic. If you don’t mind spending more money to get your woodwork to a better standard, than this is the water-based paint to go for.
I have included this paint, simply because it is reasonably priced, and you can go over the top of oil-based paint without a primer. Opacity isn’t great, so expect to need an extra coat. However, the finish is fantastic, it’s easy to use, and it’s very durable.
Bedec Aqua Advanced
I love this water-based paint! It comes in satin or gloss, and you will need a separate primer when painting over the top of oil-based paint. But Bedec are experts in water-based paint. It’s a British brand, not too expensive, is easy to use, and looks fantastic.
Johnstone’s Aqua Guard
This paint was recently voted the best water-based satinwood on the market by Professional Decorators on DFUK. You will need to use Johnstone’s Aqua Undercoat, or a similar primer when painting over oil-based paint. It can also ‘run’ a little bit, but it’s still an amazing product, and one I use on a regular basis.
Can I put water-based paint over oil-based primer?
Primers aid adhesion, seal a surface, and generally create the perfect base on which to apply other paint products. You shouldn’t have any issue painting over an oil-based primer with any paint, including water-based.
The only thing you need to do is ensure that your primer has fully cured. Otherwise, you may experience adhesion issues.
Do painters still use oil-based paint?
Some Decorators in the UK still use oil-based paint. I ran a survey for Decorators in 2015 and I found that less than 10% used water-based paint. Now it’s closer to 70%! I think a some of the old-school Decorators are stuck in their way and may never stop using oil-based paint unless pushed.
Legislation will probably continue to get tighter around the use of oil-based paint in the coming years. They already restrict the use of certain chemicals in this type of paint. At some point soon, I think oil-based paint will be outlawed all together.
Can you still buy oil-based paint UK?
You certainly can. It isn’t the same oil-based paint that we could buy pre-2010. They now regulate the amount of VOCs a manufacturer is allowed to use in a tin of oil-based paint, which diminishes the performance somewhat.
Can you use water-based undercoat over gloss paint?
One of the qualities of undercoat is superior adhesion, so using it on oil-based gloss isn’t an issue providing you get the prep right. However, don’t get your undercoat mixed up with acrylic primer, which is used on bare wood.
Can You Use Water-Based Paint Over Oil-Based Paint? – by Robin Gofton