Hi everyone, I am working on a large (24in x 34in ) shadow box that needs to be painted gloss black. It needs to be done cheaply so I used some MDF that I had laying around. I'm using cheapo spray paint from WalMart and am having trouble with the rounded edges not taking the paint. The flat surfaces are fine but where I used a round over bit the MDF is behaving like end grain-it's just sucking up the paint. I shot a primer coat and three top coats and still cannot get a nice finish. Before painting I also sanded to 220 grit so it should be smooth enough. Can anyone shed light on this problem? Thanks, Gene
Problem painting MDF
Jun 18, 2005
16 Replies
Think sponge.
You need to seal the porosity. I use lacquer-based automotive finishing putty.
The spray paints (Pressure Packs) are just to thin for MDF edges. Get out a brush and give them a coat of acrylic Black or undercoat-sealer. Sand back nice and smooth and then spray. All should be OK. Regards John
"Gene T" wrote in news:j9Mse.63118$ snipped-for-privacy@tornado.socal.rr.com:
An article in FWW and/or FHB showed sealing the cut edges of MDF with thinned drywall taping compound. Fills, smooths and pretty much seals the edges. Use before priming.
Or so I'm told. I use very little of the stuff, personally.
Patriarch
When ever I finish MDF with paint I prime the hell out of it. I use Krylon spray primer and lay it on until it looks like it will run, then I let it dry, and put on one or two more heavy coats, with a light sanding in between. Keep laying on the primer until it quits absorbing into the MDF. Greg
Now I wish I had used polar instead!!!
...working with that stuff can give you a disorder. . . . . . . . . . . . . . . . . I seldom make fun of a typo..sorry 'bout that.
You can also buy special primer for MDF too :) Most big box tool stores should have it.
-- Regards,
Dean Bielanowski Editor, Online Tool Reviews
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Unfortunately I work with MDF all too often, I find no joy out in working with it whatsoever.
I make a light wash of PVA and water and "pre-prime" (hey, did I just invent a new term?) the MDF edges with that, let it dry and then prime & paint normally. Occasionally I may also need to do some filling but I do that after priming and usually add a second coat of primer over the filler.
It works for me, anyway.
- Andy
I used shellac for this purpose and found that it did a good job of sealing the surface. After each coat (did several) I sanded the surface to make it smooth. Has anyone tried shellac as a primer? Have you found that the other methods mentioned did a better job?
I have used it ith success.
I like shellac for it's quick-drying, and it "sandability".
Oh yes, I forgot that you can add some sandarac (about 10% or so) to shellac and it makes it less "gummy" and more friable so it sands a lot better. Sandarac is a gum resin that can be purchased from some finishing suppliers.
I haven't used plain shellac, but I have used Zinsser BIN primer, which is a shellac based primer with white pigment added. It worked very well for me.
A.K.A. "Glue Size".
I know the feeling.
Ah. Thank you. Terminology's one of the problems with being self-taught...
- Andy
Lessee... glue sizing isn't about wallpaper, tenons go in mortises instead of chucks, and if a plane flies you're doing something wrong? Next I'll be told a jig is not when you hit your thumb and lathing doesn't involve plaster.
No. No, I'm not getting the hang of this. I'm going back to pointy sticks.
- Andy
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