If you have seen any of my posts before, you'll know that I usually
think I know it all but apparently I don't and now I have a few
questions. My domain consists of solid wood and the ocassional ply for
all my finished goods type production. I use MDF all the time for
fixtures, etc. but have never incorporated it in a finished piece.
I am building a fireplace surround and mantel for my new home. It
seems best to build some of the parts from MDF. It will be painted.
1. Is MDF paintable? It ssems the moisture will screw it up. Is there
some priming method required?
2. I seem to recall a variant that has a paper coating. Is that
3. What about edge prep if you are using the papered version.
4. I will have a scenario where I want to use butt joints. I want to
sort of puttey the end grain (or edge) and fill the gap of the butt
joint and sand it out smooth so it won't show once painted. Could I
just use like sheet rock taping compound or is there something better?
Yes, mdf takes paint very well - at least on what I will call the
On the "edge grain", yes, you should prime it. ordinary joint compound
and a light sanding works well.
You're thinking of "MDO". MDO is NOT the same as MDF. MDF is "Medium
Density Fiberboard". MDO is "Medium Density Overlay".
Originally developed for sign painting and concrete formwork
industries, MDO is also used for other applications as a paintable
It is a plywood product, with a paper face overlaid on the plywood
substrate with an exterior grade (usually) phenolic adhesive. MDO is
designed to have a smooth paint receptive surface. One or both faces
can be faced with paper, and is found in 4' x 8' sheets from 3/8" to
over an inch in thickness. MDO is used for short term signs. MDO is
not recommended for permanent sign faces because it is susceptible to
Warping, Water log, Mold Etc.
MDO can be edge-banded or filled. It is plywood.
However you join MDF, take care with the fasteners. Use "Spax" screws
or the like. You need a coarse thread with MDF.
Also, be aware that MDF likes to "mushroom", so use of countersinks on
BOTH sides is recommended.
I have a customer that moves every 5 years or so and insists on redoing the
kitchen each time. He is sold on MDF flat panel doors, which I cut out and
drill for Euro hinges, he spray paints the panels in his garage. He
typically lives in $500,000 homes so I don't get the attraction to this type
of door but it has the look that he is going after. That said, these MDF
doors are the only thing he spray paints and I'll have to say that his
results are pretty darn good. He does use an oil based primer and paint and
lightly sands the primed surface before applying the final paint coats. No
sanding of edges before the primer goes on.
What we have done, with good success, is to fill the edges of MDF and
plywood, which are very absorbent, with lacquer-based automotive
putty. One brand we use is called Green Stuff. It is the last filler/
putty automotive guys use before they spray on the primer. It dries
quickly and sands beautifully.
Now that's interesting. I have been using Durham's Rockhard for years
on that stuff. It dries fast, sands very well, but on occasion there
is an adhesion problem with small fills (like large nail holes) in
materials like MDF that tend to be hard and dusty.
Any adhesion problems? How fast does say, and 1/8" diameter take to
dry before sanding?
Can you put latex coatings on it as well as solvent based?
Have a manufacturer handy?
I am seeing and using more and more of this stuff in different grades,
and frankly, as poor as the wood is that I have been purchasing for
some time I am getting to the point I prefer it. I prefer the end
product, but don't prefer working with it.
Man, I miss wood. If you had asked me 30 years ago if I thought we
would be using modified cardboard for baseboards, finger jointed
nastiness from Chile for trims, sheets of termite leavings instead of
doug fir (which I thought was crap at the time) I never, ever would
have believed it.
I would never have thought about using that stuff on wood. I would
love to find a super fast dry filler. That stuff doesn't look like it
would be good for trim nail holes, though.
I am looking forward to seeing what you actually have. I <love> to
have some trick stuff to make my work easier and faster in the
The downside to using lacquer putty is that lacquer shrinks. It needs
to cure *completely* before you can sand it flush and not expect it to
shrink further into whatever recess you're putting it. Then, if you're
topcoating it with lacquer all bets are off because the solvent in the
topcoat will turn around and soften the putty all over again. Using it
to coat the "end grain" of MDF seems pretty safe though since you're not
really filling any "holes" to speak of.
Free bad advice available here.
To reply, eat the taco.
When my guys were assembling cabinets, melamine on 5/8" PB, sometimes
they'd pop a nail through the side and make a larger hole. We had this
can, with white body putty. It was made by Sikkens. We'd whip up a wee
bit with a dab of hardener and 20 minutes later flush the repair with
a sharp chisel. Fast, white, and tough.
The lacquer putty was never used for larger problems, because it does
shrink when it dries. I am not aware of any problems with the stuff
softening with actual lacquer after it had set up.
I do not know where the cut-off is in terms of hole size. It would
surely be successful in a 18ga nail hole.
I worked on the restoration of an important house in Rochester NY. The
painter there used window putty to fill nail holes and just painted
over it. No waiting or sanding. Worked great. And this guy knew his
Yes, but why would you want to? At worst, three coats of clear poly. Best
would be a shellac and French polish. If you are going to take the time to
make a nice project, don't cover up and hide the material. I use 8d common
nails too and the contrast with the heads is a beauty to behold.
Given your sense of aesthetics, I don't think we will ever see you doing one
of the Designer shows on cable TV.
On Fri, 16 Jan 2009 21:36:21 -0800 (PST), "SonomaProducts.com"
...maybe, maybe not...heh...OTOH, I've built a rather large hearth out
of MDF, with wood plant-on trim, mitered the corners and filled where
appropriate with Bondo...used poplar for the mantle and hired a boat
painter to apply a two-part varnish. Been 10 years and still standing
tall...MDF paints up great!
I thought the only appropriate finish for Cherry was semi gloss latex
paint. Maybe I'm confused.
I am covering an existing brick fireplace and mantle so I am a bit
constrained. I also have a home that is not so upscale so I want to
bring in some class but not so high end that it is over done. I am
using some classic influences and holding the stacked molding down to
a minimum. I am using an MDF backfield to be CNC'd by my buddy to
match the shape of an archway I am constructing betewwn the living
room and kitchen to tie the things together. Here is a link to my
Thanks. Yes my desing, I collected many images of classic designs and
then drummed up my own designed over the existing brick. Yes, white.
The room walls will be some ivory or slightly darker. The bicks,
unfortunately, are already painted white so I think I will try doing
them the same color as the room walls. If I thought it could be done I
might try sand blasting back to red brick. I might try it first on a
portion that will be covered. Maybe even just sanding it off a bit for
a distressed look.
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