Whatever your reason for wanting to paint mdf you obviously want to get it right. While in general painting mdf with emulsion is a relatively straight forward task there are a few crucial steps you need to follow to achieve the best level of finish possible.
What are the main problems with painting MDF?
The main issue with painting MDF is that it just loves to soak up the emulsion. Due to the nature of MDF being a very fibrous material it can just soak up paint, leaving you wondering where that new tub has just disappeared to.
One way to address this is by using a technique called a ‘Mist Coat’. A mist coat is a thin watered down first coat which essentially works as a sealer. This uses little paint but helps to seal the surface of the MDF. Once the surface has been sufficiently sealed the next coat of paint will not soak into the same amount at all.
To create a mist coat using a water-based emulsion you just need to separate some paint out into a tray or bucket and then add water. I like to mix my mist coat to roughly 60% paint to 40% water. You don’t have to worry about being too exact here. Once you have mixed up your mist coat simply paint it onto the wood using a brush or roller as you would do normally. I talk about mist coats in more detail in my can you paint straight onto plasterboard article.
Sealing the sides
One of the issues with painting MDF is the fibrous edges. These sides really do soak up paint like nothing else and can be tricky to seal. This is because they are constructed of wood fibres heavily compressed and glued together. They also don’t offer the best of finishes so many people like to seal them with something that smooths the surface to lead to a higher quality finish.
Sealing with wood filler
This is my go-to option if I want a really good finish on the edges of MDF. To be honest, though I rarely have an open end of MDF exposed. I will much prefer to cover it with trimming or with a mitred joint. The side of an MDF board has no real strength and is not intended to be exposed at all.
Sealing with wall filler
You can also use a wall filler like Polyfiller or off-brand alternative to seal the sides of an MDF sheet. Do not do this is the MDF board will be under any movement. With movement the wall filler will crack, this is inevitable.
Painting MDF with emulsion
Now comes the painting part. Painting MDF with emulsion is straight forward, just paint it on. The smoothness of your application will show in the final result. So if you are after a really high-quality finish then take it slow. Even with the mist coat, you may need to use a couple of more coats of paint until you get the desired finish. This will be partly dependent on the colour of the MDF you are using. The darker green moisture resistant MDF board will obviously need more coats of a lighter colour than the regular light brown coloured board would.
Can I use oil-based paint?
Yes, oil-based paints will work fine on MDF too. Just remember you will have extra cleaning steps when compared to water-based paints. To create a mist coat with an oil-based paint you will need to use paint thinners rather than water to thin down the first coat.
You will also need to use specialist paintbrush cleaners or turps to clean up your equipment once you are done painting.
What if I need it to be waterproof?
Water and MDF really don’t mix. Neither does water and water-based emulsion. MDF soaks up water before losing all structural integrity due to its fibrous nature. So if you need the MDF to be waterproof you will need to use some sort of sealant. A clear acrylic paint sealer can be sprayed over the painted finish to achieve a waterproof coating.
- Dries clear to create a waterproof seal
- Completely waterproof and corrosion-resistant surface
What is the best primer to use on MDF?
I just like to use a mist coat of the emulsion I am going to use. If you are looking for a dedicated primer though then you can’t go wrong with the Leyland specialist MDF primer shown below.
- Suitable for use on interior and exterior, medium density fibre board
- Low odour
- Quick drying
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