What Is the BEST Way to Paint MDF? - 9 Methods Tested

Intro: What Is the BEST Way to Paint MDF? - 9 Methods Tested

Painting MDF can be a real chore. Especially trying to paint the edge of MDF. It just drinks up the paint and takes forever to seal. It seems everyone has a different method and recommendation when it comes to painting and sealing the edges of MDF so I thought I would put 9 of those methods to the test.

STEP 1: Prepping for the Tests

The MDF test pieces were all sanded to 240 grit before applying the different methods.

For the top coats of paint I used spray gloss paint. I chose this because I thought gloss would give the best comparison surface finish between each method. Using spray paint will remove issues like brush strokes and marks left by rollers. I used Rustoleum Mode paint which is actually recommended for MDF on the can.

STEP 2: Method: Iron & Blowtorch

The first suggestion was one I hadn't ever considered before. I was recommended to use heat to seal the MDF before painting. This came in the form of using an iron and a blowtorch. I tried the iron method on the left side of the MDF and the blowtorch was tested on the right side of the MDF.

The iron was set to its highest heat and the steam function was turned off. I applied heat evenly across the left side of the MDF edge. It felt smoother but I sanded it and applied the heat again. This made the edge feel silky smooth.

The blowtorch was used on the right side of the MDF edge. I applied the flame until the MDF was evenly scorched. After sanding it did feel smoother but I applied the blowtorch again for a second coat of heat. After sanding the second coat it felt silky smooth.

Iron

• Cost: £0.00 (only cost being electricity which I can see being fractions of a penny)
• Coats: 2
• Time To Apply: 2m 36s

Blowtorch

• Cost: £15.20 (full 0.4kg canister of gas)
• Coats: 2
• Time To Apply: 24s

Results

After applying 2 top coats of paint sanding between each with 240 grit paper I was really disappointed with the finish. Before paint the surface felt as though it had sealed but the paint just soaked in and made it feel rough again.

The iron side had a flat dull appearance and still felt quite rough.

The blowtorch side felt smoother than the iron side but it was still really dull. It wasn't a great finish.

Overall I would give both these methods 0 out of 5 stars.

STEP 3: Method: Edge Banding

Edge banding has been recommended by loads of people but I've never actually tried it myself.

Applying it was really easy. I cut it to length with scissors.

I could then use the iron to apply it to the edge of the MDF. It sets almost instantly.

There are specific trimming tools you can buy for edge banding but I just used a sharp knife and some sandpaper.

• Cost: £8.95 (7.5m roll)
• Coats: 1
• Time To Apply: 3m 50s

Results

The edge banding was quick and easy to apply. Simple to trim to size and was ready for paint right away. The finish is near perfect!

It gave a silky smooth finish after both top coats of paint. It had a really high gloss appearance too.

Overall I would give this method 5 out of 5 stars.

STEP 4: Method: Wood Filler

I was recommended to use wood filler to seal the edge of MDF but I was also recommended to use car body filler. Rather than buying both to test out I opted to find a middle ground and bought a 2 part wood filler instead. I hope this will offer a good compromise between the two.

Mixing the wood filler is simple. It does have a strong odour to it though so make sure you wear a mask and have plenty of ventilation. It has 10 mins of working time once mixed.

Applying it with a putty knife was simple. I can see it taking some practice to get an even coat over a large area though. It took 30 mins to dry. Once it was sanded it was silky smooth to the touch. The smoothest out of all the methods.

• Cost: £1.99 per 100ml
• Coats: 1
• Time To Apply: 34m

Results

After applying 2 coats of paint and sanding between each the surface felt like glass. But some banding was visible. I think this is where I either sanded too much of the filler away revealing the MDF beneath or I didn't apply the wood filler as even as I thought.

It has a high gloss finish and I would say it is very close to the edge banding in quality.

Overall I would give this method 4 out of 5 stars.

STEP 5: Method: Spackle or Pollyfila

Spackle was another suggestion I had. I believe in the UK we would know it as Polyfilla so that what I got. I hope it's right.

It's really simple to apply with a putty knife. Like the wood filler, I can see it taking some practice to get an even layer though. I took 1 hour to dry and even after sanding it still felt really rough.

• Cost: £0.83 per 100ml
• Coats: 1
• Time To Apply: 1h 2m

Results

After the 2 top coats of paint the surface still felt really rough. I was surprised just how much texture the surface had.

The surface is really pitted and its given a really dull finish.

Overall I would give this method 1 out of 5 stars.

STEP 6: Method: Eggshell Paint

Eggshell paint has always been my go to method for painting MDF. It's really thick which I think is ideal for sealing the edge of MDF.

Eggshell paint is easy to apply with a roller but it can also be thinned down and sprayed too. It took each coat 30 mins to dry and after sanding it felt nice and smooth.

• Cost: £0.76 per 100ml
• Coats: 2
• Time To Apply: 1h 2m

Results

I was actually disappointed with the quality of finish on this one. It didn't have the gloss finish I'd hoped for and it was quite pitted.

The surface is semi gloss but you can see some deep pitting that reveals some of the white eggshell paint beneath. The texture on the surface is similar to orange peal too.

Overall I would give this method 2 out of 5 stars.

STEP 7: Method: Acrylic Primer

Acrylic primer has been a high recommendation from a lot of people. I have used primers and undercoats before but they have always seemed watery and thin. I've never used an acrylic primer though.

Its easily applied with the roller and it can be sprayed too. Each coat took 30 mins to dry and after sanding it felt nice and smooth.

• Cost: £0.60 per 100ml
• Coats: 2
• Time To Apply: 1h 2m

Results

The finish on the surface appeared even but did have some pitting. There was a semi gloss shine to it.

The pitting and texture is quite noticeable. Orange peel feeling like the eggshell paint but no as severe.

Overall I would give this method 3 out of 5 stars.

STEP 8: Method: PVA Glue

I've heard PVA used a lot to seal MDF so putting it to the test will be interesting to see the results.

I was advised to water down the PVA glue to the consistency of milk. So I did that but I also tried to apply the PVA neat to see if there was any difference. Both methods took an age to dry. I had to apply 4 coats of each before I got it to feel relatively smooth.

• Cost: £0.30 per 100ml
• Coats: 4
• Time To Apply: 3h 36m

Results

The resulting surfaces after the paint was applied wasn't great. Both sides, the watered down and the neat PVA looked very similar.

The texture was rough, pitted and raw feeling. It felt like the MDF wasn't sealed even after the 4 coats being applied. I didn't notice much of a difference between the watered down and neat PVA methods.

Overall I would give this method 2 out of 5 stars.

STEP 9: Method: MDF Sealer

MDF sealer is a method I have tried myself in the past and I wasn't impressed by it.

Its a really thin consistency and is soaked up a lot by the MDF because of this. Very similar application to the watered down PVA. It also took an age to apply and dry. 4 coats being needed again. It did however feel smoother than the PVA glue.

• Cost: £1.31 per 100ml
• Coats: 4
• Time To Apply: 3h 36m

Results

After the top coats of paint were applied the surface was smother to the touch than PVA glue but the finish still wasn't as glossy as I'd hoped.

The texture was still quite pitted and while it was smoother than the PVA glue, it still was textured like raw MDF. The gloss was improved with this method though.

Overall I would give this method 3 out of 5 stars.

STEP 10: Method: Control - Just Paint

As a control I wanted to try just paint as both and see how it compares. I used it as the undercoating method and for the top coats.

As you can imagine its really easy to apply. Each coat took 30 mins to dry. I applied 4 coats and stopped at that point. I thought 4 under coats would make it a fair comparison with the other methods. It felt quite rough.

• Cost: £1.98 per 100ml
• Coats: 4
• Time To Apply: 2h 40s

Results

After adding the top coats the finish was better than expected. Still not great, but better than I thought.

It felt relatively smooth although you could see areas where the MDF was showing its texture. The gloss was quite good too.

Overall I would give this method 3 out of 5 stars.

STEP 11: The Final Verdicts

The Cheapest Method

- Acrylic Primer -

On paper, the Iron and the PVA glue where the 2 cheapest methods. When I take into consideration the extra top coats they would require though I have to give the cheapest method to Acrylic Primer. Cheap and relatively quick to apply. It provides a good finish too.

The Quickest Method
- Edge Banding -

The blowtorch and iron where the quickest on paper but taking in to account the extra top coats you would need to apply I had to give the quickest method to edge banding. Fast to apply and gives a fantastic finish.

The Quality Method
- Edge Banding -

I gave it the highest star rating and for good reason. Edge banding gave the best finish. I would like to mention that wood filler gave a great finish too so it's a very close second but I have to give the quality finish to edge banding.

STEP 12: Closing Thoughts

After taking into account all the different methods I will be using 3 in particular moving forward. I'll be using edge banding and/or wood filler when the edge of MDF will be a prominent feature of a project. I'm not a fan of the costs involved but the finish quality would be worth it for important projects. I would use edge banding on flat edges and wood filler on edges that have a profile like a round over or a chamfer as edge banding would be awkward to apply to those edges.

For basic sealing of MDF edges I'll be using acrylic primer. I did hold out hope for my suggestion of eggshell paint but acrylic primer is cheaper and gives a better finish. It will be ideal for the projects that aren't as crucial. Edges that wont be easily seen or projects that don't require such a high quality finish.

But what do you think? I hope you found these tests helpful. Painting MDF is a pain but I think these tests have shed some light different options available and the costs/times involved with each.

Comments

[GottaLoveProjects]

I stumbled upon a great method for sealing MDF edges, chilled CA glue (non-gel). Putting CA glue in the freezer overnight increases the set time for the CA but still retains a low viscosity. You simply spread it on an edge and it will penetrate before setting rock hard. Once set, you simply sand off the 'fuzz' and coat with primer.

[mrscannone4]

I recently sealed a piece of MDF by using Kilz oil-based primer. I brushed it on and it worked great. I had sanded the surface but I used too coarse a grit and it made the surface very rough. For the edges, I wanted a rough rock-edged look anyway, so before I primed it, I mixed up a little Bondo filler and just applied it roughly to the edges by hand. It stuck great and looked great. I then sanded down the sharp points on the bondo and primed the whole thing with two coats of the Killz, using a brush. I could've used a roller but I didn't care so much about brush marks. Sorry, I didn't get a photo of the piece with just the primer before painting. Next I applied multiple coats of spray paint, acrylic paint sponge dabs, and polycrylic. I'm going to be using this for a bathroom vanity top. Cheers!

[onetruegod]

Well executed comparison.
A question; can you get edge banding in suitable colours so you don't have to paint it?

Regarding the chart in step11 you have cost /100mL. It would be better to have cost per unit area or length of edge, as this is a more relevant measure that takes into account differences in application density and layers.

Also the cost of "only paint" should be zero as you have already painted while the other sealants still need to painted.

[lschwartz]

Well done! I'm installing shelving in a closet. Because it is just storage, the finish isn't really important. So, saving all kinds of time and cleanup, I'm using contact paper.

[TechTheaterLifer]

I've been using MDF for scenery elements in opera and stage productions for years and the difference between the face and any form of cut or shaped edge has always been a problem. The best solution we found, particularly for large scale stuff is to use shellac on the edge. You can brush it on full strength, but cut it up to 50% with alcohol if needed to speed application. What happens is that the shellac makes all the little fuzz and points stand up and then harden. They get almost crispy. Once the shellac is dry, in 30-45 minutes, sand lightly with fine sand paper. The shellac penetrates the spongy nature of the MDF and hardens and smooths the edge when sanded. Anything water based just makes the wood fibers absorb the water and swell making the problem worse, but once the shellac has sealed it you can top coat with primer for the best finish or latex paint or anything else if you're in a hurry. Without sanding it still looks as bad as always but if the surface texture is the concern, shellac and sanding has been a reliable solution.

[Rwags]

I concur. Shellac will seal and harden the edges.

[tarpho]

I concur. In my experience, whatever you use, for the best results sanding will be necessary to make the edge as smooth as the face. Other alternatives - cyanoacrylate (superglue) - expensive, fumes are toxic, very hard finish. Epoxy - doesn’t stink, pricey, most not UV stable.

[boffincentral]

I came down here to suggest exactly this, though I have not tested this on MDF.

I do this with timber end-grain; sanding up to 800 or sometimes 1200, depending on the timber, if I am using an oil finish. When it is done right, timber end grain is also beautiful with an oil finish rather than the unattractive muddy mess if you apply oil finishes directly to end-grain.

[charlessenf-gm]

I've never spent so much time watching paint dry ;) !
Good for you!
It appeared that you were only sanding with 240 Grit paper. As well, holding the paper in your hand and pressing with your fingers. No, no, no! Better finishes achieved by using a series of grits that are fixed to a Hard Smooth Surface such that even pressure is applied to (the edge, in this case) of the material. I would suggest getting a tack cloth and using it between grits (to remove loos debris between grits) as well as (in this case) sanding in one direction.
Do not use the sheets that have sanded 'finishes' on the bare MDF and, to be most Scientific, do not use paper earlier employed to sand the primer'ed edges to sand the edges coated with another finish (and visa versa).

You might want to share details of how you cut the sample edges - 32 carbide teeth on a ten-inch table saw? An eighty-tooth Timberwolf blade perchance? Surely not a jig saw!

Admirable job, great detail.

One approach is to avoid any exposed edges of the MDF in the finished piece. This can be accomplished by using the MDF for relatively 'hidden' parts of the project. Another approach is to glue a veneer of 'real wood' (similar to the edge banding approach) or thicker strips of wood to the exposed edges (mitering them at the corners).

I would think, knowing how MDF likes to swell when moist, that a lacquer sealer might be the best first coating of those edges - and two coats at that. A moisture barrier, if you will.

In the one piece that diluted glue was applied to, it appeared that the water had penetrated into the material significantly. All wood and wood products (too, I suspect)

[charlessenf-gm]

Wood is hygroscopic - seal the MDF before applying anything that contains WATER. here are Shellac based primers that can be sanded, shellac itself, of course and the Sandable Primers used in automobile repair shops are all good 'waterproof coatings that can be sanded smooth enough to 'take paint' and show every failure of the preparation.

This was a good project, well presented.

Well, for an 'average joe," of course. ;)

[bpark1000]

Beware edge banding: in time, it falls off! It tends to get caught by objects sliding over the MDF, and "picked" off. It is especially bad on sharp corners. Its bonding agent is basically "hot melt" glue, and that breaks down to powder with age.
If you are that picky about finish, don't use MDF! Use quality plywood, and epoxy bond half inch thick boards (not veneer!) to the edges.
TechTheaterLifer has it right for stage props that are not viewed close-up. Make sure the shellac is fresh.

[LeeL84]

I use a wood hardener the sort you apply to partially rotten wood. It's very thin and absorbed quickly. Several coats and then rubbed down before painting.

[katou]

I made a bunch of trim out of MDF and I used Kilz oil based primer because it is the only paint I've found that truly sands well.

It worked ok, but still took 2 coats.

I decided that next time I did it, I'd use autobody filler, polyester resin thinned out with a solvent, or a thin coat of epoxy.

I'm sure one of those would work very well.

[katou]

BTW, if you've never used Timbermate water based filler, you've got to try it. It is hands down the best filler I've ever tried and sands like a dream.

[rogert0947]

My spray paint supplier suggests grey primer. Not tried it yet so I can't say what the outcome will be.

[ToolboxGuy]

I have to say, this was a very complete examination of the options! Nicely done!
If I had a job which needed a fine finish, I don't think I would consider MDF as my material. If I had to go that route, I'd use a veneer over the top and contact glue it!

[jwilliamsen]

Any preparation that is water-based is going to require more preparation. The water will soak into the fibers of the MDF and cause them to swell and "fur up" - so water-based paints and PVA glue will make more work. It's the same concept as wiping down any project you plan on using a water-based finish with water first, sanding down the fuzz, then repeating until the wood fibers no longer "stand up" - then applying your finish (this is typically only necessary with water-based finishes, dyes, and stains).

It's kind of unfortunate that you didn't get to try the Zinsser BIN primer. BIN is shellac-based and the main solvent is alcohol. It doesn't raise the grain or swell the fibers, it dries very quickly and sands easily (doesn't clog paper). Interestingly, it cleans up with straight ammonia. It's a fantastic general-purpose primer - and it can be tinted as well if you plan on a dark topcoat.

Of course, ALWAYS consider what you plan on top-coating with as some topcoats are not compatible with certain primers (possible bubbling, peeling, wrinkling, etc).

The best putty-based solutions I've found for filling the pitting are 1) Glazing or Spot Putty - this is just a really thick laquer-based primer that comes in a tube. It flows on and sands easily and is generally easy to work with. It's designed for auto-body work, so pit-filling and smooth surfaces are what it's formulated for (just be careful with laquer-based top coats). 2) Finishing Putty - for more robust filling larger areas. Finishing Putty is more universally compatible with finishes and again is designed for filling imperfections and smooth finishes.

The best solution I've found is one that requires a bit more of an investment: Catalyzed Filler Primer (like Keystone #8882). This is another auto-body product and is best applied via spray gun. Filler Primer builds and cures very quickly. It sands very easily and doesn't clog sandpaper. It's compatible with pretty much any finish you would want to use and provides a great bond for pretty much any topcoat (it's a good idea to prime MDF with some kind of primer before painting). Catalyzed primers (urethane and epoxy primers) can often be purchased in a spray can as well. They will have a "squib" or button that you activate to inject the catalyst into the paint - so once activated the paint in the can will have a pretty limited shelf-life - but they are convenient and less expensive.

Oh - one other thing to try (I don't know if this would work) - a combination of two techniques: Apply a couple of heavy coats of PVA glue and once dry, use an iron to smooth the surface (PVA will "melt" and flow when exposed to heat as it never really becomes a solid).

Thanks for putting this instructable together. There were a few things you covered that I was wondering, "Will THAT work?" and my assumption was wrong in a couple of the tests - so thanks for saving me the trouble :)

(Sorry for the novel - lol)

[MikeLamb]

Great video! That was a lot of work!
My advice would be to remember that any type of paint is going to be a film, so it will only cover the surface profile/topography that exists. If you wanted to use paint as a filler, you could roll the edge, then use a putty knife to remove the wet paint film from the highest/raised surfaces. and fill in the texture that way.
It's like paving a road, if the crew doesn't fill the pothole, the fresh layer of asphalt isn't going to help.
Fillers/putties have a much higher solids content (meaning they will shrink less) and will perform better for filling in the potholes & creating a smooth/level surface.
Most people assume a "sealer" will create a uniform surface, when they are only meant to seal the surface porosity to prevent any further moisture wicking into the base material. This will help give a more uniform appearance to your topcoat, but it will not smooth/level the surface.

[Alex in NZ]

Thank you! This is just exactly what I'd hope to find if i searched for how to paint the edge of MDF. I'm surprised that PVA did so poorly, as that would have been my guess for a decent result, but you can't argue with a well-controlled experiment. Thank you for sharing your work :-)