What is the best way to paint mdf?

[stevev]

Just using spray paint on mdf is hopeless, so I was advised to use a brush on oil based paint, your own choice of color, and then sand, coat again and sand, coat again and sand, on and on until you get a completely sealed and uniform finish. The end grain of mdf seems to be the most difficult to finish using this method and the multiple coats and sanding between each coat seems a lot of work for the results. Is there a better way to use paint on a mdf cabinet, like maybe coating the mdf and end grains with fiberglass auto body filler before painting? It seems that might reduce the number of paint layers used to seal the end grain and surface. What is the best approach to a painted, or spray painted cabinet?

[evilskillit]

Re: What is the best way to paint mdf?

I haven't tried this yet but from seeing what everybody else has done it seems like your best bet might be to skim the whole box in bondo first then lay down some paint. Or get some "high build" primer specifically made for applications like sealing mdf end grain, something like this: http://www.idealtruevalue.com/servlet/the-55931/Detail

As for the actual paint, well after that do whatever you were going to do anyways.

[fastbike1]

Re: What is the best way to paint mdf?

There are a number of threads about painting mdf on this forum. Several "favorite" methods.

In general you need to seal the surface first. A sealer/primer such as Kilz, Zinsser, etc is a start. The edges will print through unless you cover them with something like spackling, bondo, etc. You can't paint enough to cover the end grain.

While Taterworks has recently commented that he thinks veneer is passe, painting mdf is just one of the many hassles of working w/ the material.

[jerryanderson]

Re: What is the best way to paint mdf?

You need to seal the MDF before you do any painting!! Methods differ from person to person, but a good way to start is with diluted wood glue! Elmers wood glue or Tite Bond are good brands to work with! Some just rub straight glue into the end grain and and brush on diluted glue over the rest of the project! Dilute glue somewhere between the consistancy of milk and cream and brush on with a foam brush. Personally , I just brush on diluted glue over the entire project, let set a bit and go with another coat.

I usually let this dry overnight, then lightly sand with 220 grit sandpaper for a smooth finish! wipe down then go over the project with a coat of clear poly. Let dry good then lightly sand with 440 grit. Check for runs and sags and rough edges. These may need sanding with 220 to smooth out. Wipe and clean good and you should be ready to prime and paint.....

[DIYNut42]

Re: What is the best way to paint mdf?

It is possible to get a good finish just using rattle can paint. I've had good luck with using a primer/filler before painting. I lay down a few coats, then sand that down with the finest sand paper you can get your hands on. Repeat till you get a nice smooth finish, then spray with several light coats letting each one dry between coats. Spend a little extra on the higher quallity paint if you're going to spray can it. You will appreciate the difference.

[NickS]

Re: What is the best way to paint mdf?

Sheetrock joint compound works good for sealing the end grain and sands pretty easily. Always use an oil, alcohol, or lacquer base primer. Water based primer will swell up the grain on mdf. After that, latex or oil based (preferred) paint will work over the primer.

[evilskillit]

Re: What is the best way to paint mdf?

My only complaint about sheetrock joint compound is that it chips and digs easily, its fairly soft and brittle. I used it on one of my projects and it works ok, but especially on small speakers you might take with you on the go to show off to people it seems a lot more susceptible to damage if you build up any thickness than some of the other options would be.

[Paul Carmody]

Re: What is the best way to paint mdf?

I've tried a host of things, always looking for the simplest solution. I can definitely get nice results with a rattle can, but prep work is a must. I have learned that you HAVE to seal the endgrain of MDF somehow. My personal preference is to go over the joint with Bondo, then sand that down until the seam is no longer visible (no guarantee that it'll never return, but it's the best I've found so far).

Once the endgrain is sealed, then you gotta seal the whole cabinet before spraying paint. Here are three things I've tried

1. You can go over the whole thing with Bondo. (I did this on one project; my arm still hurts from all the sanding, when I think about it) Some may suggest Bondo mixed with Plastic Honey (sp?). I believe this is what Aaron Hero does, along with heating the cabs methodically to "force" the joints to move until they stop telegraphing.

2. I have tried automotive primer in rattle cans to prep MDF. It's OK, but it takes several coats, which then have to be sanded down before using color. THe dust created by sanding primer is very messy (ever gotten xerox/laser printer toner all over?)

3. The simplest, most reliable method I've found to paint MDF is to thin wood glue with water until it's about the consistency of wet paint, then brush it on the entire cabinet with a foam brush. When that's dry, I sand it down to 220 grit sandpaper, apply another coat of water-thinned wood glue to the whole cabinet, sand that down to 220. After those two coats, the surface is hard, uniform, and ready for action. (It looks like crap, though.) I apply the rattle can of my choice.

[Æ]

Re: What is the best way to paint mdf?

Just using spray paint on mdf is hopeless, so I was advised to use a brush on oil based paint, your own choice of color, and then sand, coat again and sand, coat again and sand, on and on until you get a completely sealed and uniform finish. The end grain of mdf seems to be the most difficult to finish using this method and the multiple coats and sanding between each coat seems a lot of work for the results. Is there a better way to use paint on a mdf cabinet, like maybe coating the mdf and end grains with fiberglass auto body filler before painting? It seems that might reduce the number of paint layers used to seal the end grain and surface. What is the best approach to a painted, or spray painted cabinet?

I kind of did something like that, brushed on some oil based paint over a small area as a test. Will definitely have to sand it quite a lot. Maybe next I'll try some heavily thinned oil based. Personally I'll never ever use anything water based on MDF. MDF and water are a no-no!

[davepellegrene]

Re: What is the best way to paint mdf?

I have found using oil based bin 123 works really well for sealing the end grain and also the rest of the sheet. It takes several coats. This is sprayed with a rattle can of satin bronze over top.







If you are trying to hide the seams from telegraphing through the paint the trench method seems to be the only one of all my experiments that has worked. A few of them worked pretty well but the trench is the only one that shows no signs at all after about 9 months. See Trench Method in my links below for the seam method and my Picasa link below you can see all the methods I experimented with. Just scan to the bottom of the Picasa page once you click on the link.

I have also found heating the MDF is not that critical. Moving it to a controlled environment for several weeks before finishing seems to work fine.
Dave

[fastbike1]

Re: What is the best way to paint mdf?

All of the required prep work is one of the reasons I don't use mdf.

Add the dust, some unfavorable material properties, and increased cost.

Not worth it to me. If I'm not using plywood or hardwood, Chris Roemer has converted me to the new particleboard.

[lunchmoney]

Re: What is the best way to paint mdf?

MDF and water are a no-no!

Simply not true, but I'm weary of this debate. Wood glue cut 50/50 with water is a far cry from water.

I prefer wood glue diluted with water (yes, I've also tried shellac), and I have the results to back it up.

[r-carpenter]

Re: What is the best way to paint mdf?

dave, I hate to be a party popper here and believe me then I am critiquing you, it's only out of good intentions.
MDF expends and contracts differently thickness wise and lengthwise. This is why, then **** joints are used, ghosting takes place after a while. Instead of **** joint, use 45 miter or lock miter. Problem gone. Glued up edges of mdf now expend and contract at the same rate. Now, you can round over and glue size or veneer without much consequences.
Bondo and MDF do not have same expansion and contraction properties and while you have seal your channels in with the finish, it's a potential problem (and I hope I am wrong). Besides it's very time consuming.

[r-carpenter]

Re: What is the best way to paint mdf?

Simply not true, but I'm weary of this debate. Wood glue cut 50/50 with water is a far cry from water.

I prefer wood glue diluted with water (yes, I've also tried shellac), and I have the results to back it up.

glue sizing with 50/50 mix is a very common practice among pros.
All tho one could use Ranger board instead of MDF and it's designed to take finish on the edge without glue sizing.

[tech9_79]

Re: What is the best way to paint mdf?

has anyone tried just laminating the whole box with something like masonite?

Dave that bronze satin looks great, ive been wanting to move away from black gloss..ugh.. what brand is that?