Ok- I know this is a really tacky question to ask in this forum… I do most of my work in good quality solid woods, like most FWW subscribers, I suspect.
However, now I am making a subwoofer, and it’s going behind the sofa so I want to take the quick and dirty approach. 3/4″ MDF box. Painted with a short-nap roller to get an “orange peel” finish that hides small surface defects.
However, I’ve noticed that the inner core of an MDF panel is a different, coarser consistency than the surface, which is quite smooth and polished. Even if I run a router with an edge trimming bit over it and sand a bit. And I found that if I just prime and paint the boxes, this coarser texture comes right through. I don’t want to mess with a lot of sanding and multiple coats of paint on this project. Is there a grain filler that will smooth out the end “grain” of the MDF so it takes paint the same as the face of the panel?
Thanks in advance.
– David
Edited 3/9/2003 3:22:22 AM ET by David B
Replies
There are special heavy bodied primers made for sealing the edge of MDF H-D carries one other wise a couple of coats of shellac on edges , some Dap spackling ,sand it back and paint.If I am spraying I use a lacquer base product that is high building made for MDF.BY the way MDF is ideal for speaker boxes because of the mass
glue size-50/50 mix of white or yellow glue & water. brush it on the mdf edges, let it dry and sand it smooth.
Bob Lang
http://www.craftsmanplans.com
Hi Bob,
Your suggestion is what I've read in the 2 Commercial Magazines that I receive.
this was in the forum last week for sealing the milled edges of m.d.f. it was i believe, sherwyn/williams vinyl sealer cut with lacquer thinner 50/50 mix. it's probably meant to spray , i cant see where a brush, with a sanding with 320 grit sandpaper. why that wouldnt work... good luck.. bear
Edited 3/9/2003 10:12:42 PM ET by the bear
Fast drying drywall compound (spackle) does a good job under paint. It fills the voids and sands very easy. A couple coats of pigmented primer (like Zinsser), applied to the edge with a brush and sanded between coats, should work as well.
When spraying an MDF shelf, I use a high solids primer and spray the edges with 2-3 passes as I spray each side of the shelf (total of 4-6 passes on the edges). Vinyl sealer will work as well, though I would not thin it at all, and it will take more passes as it doesn't have as high a solids content as a pigmented primer.
Paul
F'burg, VA
In the past 15 years I have built hundreds of cases for a museum out of MDF, (well med-x, basically the same thing) and we seal the exposed edges with spackle. Lay it on, sand it smooth and you're good to go...
Thanks to everyone for the great suggestions. I'm off to the store!
I've had good luck with giving the whole thing a coat of shellac and then using either spackle or Durham's Water Putty to fill in the "end grain". Also, another finish I've used for MDF speakers/subs which is pretty forgiving of surface defects is Rustoleum's Hammered Metal Paint - gives a nice textured surface.
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