Painting MDF - what works?

L

lamarth

Limp Gawd
Joined
Sep 22, 2004
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376
Hi-

As part of a case mod I'm using MDF (medium density fiberboard) to create a new front panel for my PC case. I realize that the surface will need to be prepped for painting, but what to use? What works good- just plain primer for wood or is there something special I need to use on this stuff?

Thanks!
 
I tend to coat all my MDF with fibeglass resin as it hardens to a paintable surface and doesn't soak in. A good primer will still soak in, so use several coats, then paint. You could consider using a furniture-grade plywood instead. The price difference won't be too much in a small piece like that, and you may even save money without the need for multiple coats of primer.
 
Kil4Thril said:
I tend to coat all my MDF with fibeglass resin as it hardens to a paintable surface and doesn't soak in. A good primer will still soak in, so use several coats, then paint. You could consider using a furniture-grade plywood instead. The price difference won't be too much in a small piece like that, and you may even save money without the need for multiple coats of primer.
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Well I thought of using plywood, but went with MDF because it was 'grainless' and seemed easier to carve/cut. The cuts seem to be a lot cleaner too than what I've experienced with plywood.

So I'd probably be better off with fiberglass resin then? Would I need to thin it out or just use it straight?
 
You're right in using MDF for "carving" since plywood will splinter if you use a router on it and are not experienced in doing so. If you want something solid like that, you could even go with a piece of solid wood like Cherry or Poplar. Poplar is very cheap and is easy to work with. Although I dont know your exact plans so I can't direct you too much. As far as the painting, you can use any sort of primer on it. It will soak in at first but 3 coats should do the trick.
 
Plywood is a lot easier to cut than MDF. You'll need special tools for working with MDF as standard wood cutting tools dont work that well. Good luck with your project!

--
Cheese
 
Yea the one thing I'm finding out with MDF vs. plywood is that it doesn't cut well. Drills great but it's slow to cut. I'm using a fine-blade on it though so that might account for some of it- but it gives a smoooth finish to the cut. But I will be doing a little routing on it to shape edges, so splintering is the last thing I need :)

I need to get a worklog up, I realize that would help. I need to sit down and get all the pics uploaded to a host, first....

Thanks for the tips!

David
 
K here's your advice:


Polyprimer.


I've never done it over mdf alone but I'm sure it works.. Usually I use mdf as framing, then fiberglass (and bondo), then polyprimer. The polyprimer is thick as heck but it'll cover almost any holes in the bondo or fiberglass. Then you do the regular painting and blam.


It's like 60 bucks a gallon though and it takes a big paint gun tip to use.
 
Qtip42 said:
It's like 60 bucks a gallon though and it takes a big paint gun tip to use.
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Ow.... don't suppose it's available in pints and can be thinned and brushed on?
 
you might could use a latex primer and paint, but i dont know what kind of look you are going for. i dont know if you could use a water or oil based paint on top of a latex coat.
i just know the latex wont soak in as bad, and will stick to the surface better.
 
Use oil based - water based will swell up the MDF. Also, plan on multiple coats since the end grain will soak it up like crazy. Be prepared to do lots of sanding. A few coats of wood sealer before primering will help. Some people have used Bondo or wood fillers to help seal the edges.
 
I build custom beerpong tables out of MDF (www.theliquidconcept.com), and the best way in my experiences to go about painting MDF is to sand it down in increments, 80 on edges, then (120-2xx-4xx), put a sealer-primer on it, then paint primer, and then paint. You want to make sure each step is the same base (oil or water) . I usually use a roller, because you will get brush lines with a brush, and it's hard to get even coverage on decent sized pieces with spray paint. With latex paint the panel will dry pretty smooth with a roller. If you're going for a perfectly smooth finish (like a car), you'll want to look into a spraygun setup
 
jojor512 said:
I build custom beerpong tables out of MDF (www.theliquidconcept.com), and the best way in my experiences to go about painting MDF is to sand it down in increments, 80 on edges, then (120-2xx-4xx), put a sealer-primer on it, then paint primer, and then paint. You want to make sure each step is the same base (oil or water) . I usually use a roller, because you will get brush lines with a brush, and it's hard to get even coverage on decent sized pieces with spray paint. With latex paint the panel will dry pretty smooth with a roller. If you're going for a perfectly smooth finish (like a car), you'll want to look into a spraygun setup
Click to expand...

Ok, so before priming I would need to 'break' the surface by sanding everything down before applying the primer. But it sounds like I wouldn't be able to do any sanding after the primer's been applied? I was planning on using enamel paint as the whole PC (along with the MDF faceplate) will be painted the same color- would this still work (as long as the primer is compatible base-wise with the paint) ?

BTW I'm not looking for a perfectly smooth 'gloss' finish if it helps. Something more of a flat to semi-gloss at the most....
 
sand down any surface imperfections, then put on a sealer, preferably a sandable sealer. After that just follow the instructions on the can - they'll probably say to use something like 400 grit. do that, wipe it down with a tack cloth, then put on the primer matched to your paint, and then paint. You probably won't have to sand the primer, I usually don't even let it dry all the way with the paint I use.

All of this might be a little overkill for what you are doing, but if you just primer and paint your MDF piece, the flat part will look fine, but the edges will look different because they will soack up more paint and primer. Using a sealer will give it a consistent look.
 
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