Do I need to prime mdf before painting it?

So you’re just about to embark on the quest of painting some MDF and are not sure if you need to prime it before painting. Can you get away without priming? Or is it essential? Let’s find out!

The short answer is no, you don’t need to prime MDF before painting it. Most paints can be applied to MDF without any need for a primer.

To demonstrate this I have a few pictures to show you. As part of my regular testing of all things paint I have painted lots of different paints onto MDF. Things like gloss and Hammerite.

When I apply these paints to MDF I always do two samples, one primed and one not. This is to test whether priming the wood before makes any difference to the paint finish.

I always find it makes little, if any, difference to either the paint finish or the durability of the paint.

There has, however, never been a downside to priming. So if you have the primer and the time, there is no real reason not to prime. After all, it would make your father proud.

Painting MDF With Gloss

So it’s all well and good me saying you don’t need primer, but where is the proof. Well, let’s get into that, as I do have plenty of proof to show you. I think we should start with some MDF painted with a water-based gloss (Leyland Trade).

Above you can see the painted MDF samples. The first thing you will notice is that there is no difference in colour. The paint has not soaked into the MDF on the unprimed sample, leaving a patchy finish like some people say it will.#

In fact, I would say there is very little to tell these samples apart, hence the need for the masking tape note!

So we know the finish looks the same, but what about durability. Now until these samples have been lying around for years I have no real way to test the ageing of the paint. I will hold my hands up here, this is the only hole in my meticulous experiment.

What I can test though is how well the paint has stuck to the MDF, also known as the adhesion. For this, I like to do a scratch test.

Scratch Test

So now the Gloss paint has had time to dry and properly cure it is time to see how well it has adhered or stuck to the MDF.

For this test, I grabbed a large price of rough-cut c16 timber and rubbed it across the melamine surface. This is a really tough test to see how well the paint has adhered to the melamine.

I feel that rough cut c16 timber is a good test medium as it is not too hard but not too soft. If I used something really hard like metal then not much would stand up to it and the test would be pointless.

On the other hand, if I used something too soft it would never scratch anything and again it would be pointless.

So here are the scratch test results. The unprimed sample has held up just fine, if anything even a little better than the primed sample.

Still not satisfied? Well, let’s try another paint, this time Hammerite. I know, Hammerite is metal paint, not wood paint. But I did an interesting experiment where I painted Hammerite on lots of different wood types, including MDF.

Painting MDF With Hammerite

I did this test a long time ago now, which means I actually have some results over time to show you. Let’s have a look.

So here we have two images. The top has been primed, the bottom has not been primed. They have been painted with Hammerite on the left and gloss on the right.

You can see on the bottom photo that the gloss has actually dried a little patchy. So if you are painting a dark colour then this may be an issue. It is definitely nothing two coats of paint wouldn’t fix though!

Then these samples were then moved outside to see how they would hold up over a British winter, time to see the results. These photos are 6 months later.

This shows that the priming has really made no difference to the paint!