[OP]
Member
OK,
I have essentially a box built out of MDF. The screw holes have been filled with drywall mud & sanded. I'm going to paint the entire thing, then I need to clear coat it for a nice hard finish.
Can someone offer some advice on:
What kind of paint do I should use?
What kind of clear coat I should use?
Will waterbased paint (latex?) + waterbased varathane work?
I haven't done this type of project before, so I appreciate the input.
Thanks.
Member
I would stay away from latex and use an acrylic or enamel.
If you use either of these, I am not sure why you would need a clearcoat. Just use a few coats of a decent acrylic or enamel, and make sure to use an adequate primer.
By adequate primer for MDF I will toss Zinsser's B.I.N. into the ring. Covers almost anything uniformly and almost anything sticks to it. Lowe's has it. Others too I'm sure.
"A hen is only an egg's way of making another egg".
– Samuel Butler
[OP]
Member
sweet. Thanks. No Lowes up here, I'll see what the Borg has...
Contributor
My experience with waterborne finishes and MDF is not good. The water in the finish raises the "grain" of the MDF, and gives a very rough surface. I'd prime the MDF with a solvent-borne sealer -- shellac, lacquer (real lacquer, not waterborne "lacquer"; Deft is a brand of brushing lacquer), or even varnish. The advantage of the first two is that they dry faster than varnish.
Member
I've had success with Kilz over MDF. I don't bother to sand first. I'll put the Kilz on, let it dry good, then sand. 2 coats of Kilz, sanding after each, and you'll be good to go. I too would stay away from Latex. An oil based paint with an acrylic clear should be ask. As at the professional paint store where you will buy the oil based paint.
Member
Steve, I don't know what quality of finish you are trying to achieve but if you are looking for something with a flat, uninterrupted surface I would pay particular attention to that drywall mud covering the screw holes. That stuff has a tendancy to shrink. If your surface is to be leveled and rubbed out you likely can't build up the cement above the hole. If you can't build it up the screw hole is likely to telegraph through the finish - maybe not straight on but examine it under raking light to be sure. MDF can finish beautifully but I agree with other poster(s) to lay down a coat of shellac to seal it before applying topcoats. It might take a few coats of shellac as it is pretty "thirsty" stuff, especially on the ends and any routed profiles.
[OP]
Member
Yes - I've had good results with Kilz over OSB, so I think I'll prime with Kilz, then apply an OIL based paint over that. Then I'll decide if I want to add a varathane to toughen it up.
Thanks for the input all, I really appreciate it. I'll show you the result when done - hopefully by the wknd.
s!
Member
I've used Varathane's Diamond Interior water based over acrylic on MDF with great results and no problems. Just like suggested earlier 2 coats of good primer and sanding leaves a good smooth base for your finish coats
Moderator
Ditto on the drywall mud as a filler. I'd dig that out and use a wood putty filler. Then prime with an oil based primer; sand between coats.
If the box is small, the easiest, best looking finish will be spraying. If you don't have a sprayer, I'd use a can or two of an aerosol enamel. Rustoleum or better.
I've used some Minwax polycrylic and Cabot waterbased poly over latex paint. Regardless of everyone's experience, I've seen them yellow with time. I've also used Target USL over paint and it did NOT yellow (gotta spray it though). However, something's always not felt right about applying a 'hard' finish over the 'softer' latex.
Member
Dry wall mud is perfect. I've posted this technique for years. You can use your mud straight or cut it a little with water. Trowel it on with a broad knife and trowel it slick. Let it dry to a haze and sand with 220. Bin pigmented shellac is a great undercoat or you can use a high build lacquer, sanding between coats. Use lacquer, oil, latex, poly, whatever. Joint cement is a great filler for MDF. You can make MDF look like fine china.
Phil in Big D
The only difference between a taxidermist and the taxman, is that the taxidermist leaves the skin. Mark Twain
Moderator
I'll defer to Phil's experience, but my experience with drywall mud as a HOLE filler for screws has been bad. It shrinked on me. I haven't had the problem with putty.
If yr gonna do drywall compound, I humbly suggest you use it as DRY as possible; the more water you add, the more it'll shrink.
I have used drywall compound to seal unfinished edges of mdf. It works ok for that.
Member
I don't know what product you mean by "Varathane". Varathane is a brand name for a family of products. Some are waterborne finishes and some are oil based.Originally Posted by Steve Canada
No waterborne finish will be as "tough" as an oil based paint. Even an oil based clear will not add any further protection. After all, oil based paint is basically oil based varnish with opaque pigments added. The paint itself is as tough as it gets. Plus, any oil based clear finish will be amber in color to some degree. The amber color will somewhat change the color of the resulting finish.
Just go with the paint and put on a couple of coats.
For the future, I have found the best way to fill MDF is to use a two part polyester filler like Bondo. It will not shrink over time. It's also a good way to seal the edges of MDF.
Howie.........
Member
Exactly, Varathane is the brand name and the line is Diamond then in that line they have interior and exterior products. I know most oil based products are tougher but just passing along that this water based product did work well if you are leaning toward a water base.
Contributor
Avoid the drywall mud.
Instead, use Bondo (they sell a home projects grade). It dries right now, does not shrink, takes paint very well, sands easily, and can be machined. (I routed the stuff after I filled a boo-boo...no blowout.)
Prime with oil base, then two top coats of oil base enamel.
kreuzie
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