Sealing MDF Edges

drywall compound. its messy but it works. make it a little watery, slather it on with a finger, let it dry, buff it smooth. got it from FWW, i dont remember which issue.

-- "Democracy is by far the worst system of government. Except all the others that have been tried." ~ Winston Churchill

I thin some solvent base or water base wood filler and spackle it on all the edges (very time consuming). You don’t have to put it on thick, just enough to fill. Or I use a thickened type of sealer ( something compatible with your top coat paint). Once both methods are dry (using either-or), sand smooth and paint(seal) the entire surface. Let dry, sand, and refill any areas that need it again. Now move to the first top coat. Check for imperfections, fill and sand, then apply finale top coat. I use Lacquer, and I use this method on high gloss finishes. Of coarse there is wet sanding and buffing in that process also. Painting MDF to a flawless finish takes time and patience and a lot of filler or numerous base coats and sanding. Good luck. Bob

-- Built in a Barn Bob

to be honest, it wasnt worth the hassle for me….i did the trim in my kitchen like that, and then swore i’d stay away from mdf and just use poplar from now on, to hell with the cost. thats just me tho. i love to cut, love to install…hate hate HATE to finish.

-- "Democracy is by far the worst system of government. Except all the others that have been tried." ~ Winston Churchill

I have not had that problem at all with MDF. Could be that my projects are finished with conversion varnish or lacquer and not paint.

I second what sean said. 5 minute hotmud is what I use and it works pretty good

-- Childress Woodworks

A painter I know showed me how to seal the edges of plywood and mdf with latex painters caulk if you are painting it.

-- Dan, Sterling Alaska, Before you criticise some one, walk a mile in their shoes...then you will be a mile away and you have their shoes!

Have you tried using glue sizing? Basically watered down glue. Sand your edges really well, put the sizing on and let it dry then lightly sand and add another coat and let dry and sand again. You should now be ready to finish.

I sealed the MDF on the project below using this process and it is 90% MDF.

-- //FC - Round Rock, TX - "Experience is what you get just after you need it"

cool shelf

-- Dan, Sterling Alaska, Before you criticise some one, walk a mile in their shoes...then you will be a mile away and you have their shoes!

yes, maybe painting is good , (this is not in line of my business , i just work at plywood manufacture in china)

-- Everything is possible!

I read in one of my wood rags that this guy uses water putty (same as plumbers putty?)to seal it but he was gonna spray paint his project so not sure if that will work for you.

-- Pie

I’ve used the drywall mud method. Definitely works but as stated very messy. Next time I’ll try the glue sizing method using watered-down yellow glue.

-- You're a unique and special person, just like everyone else.

This is what I’ve used, you can mix as little or as much as you want, Durham’s Putty, this is what we used in woodshop at school. http://www.waterputty.com/

-- Only the Shadow knows....................

Durham’s Rock Hard. Great stuff. Works well to seal MDF edges.
Spackle, right out of the can, is faster for edges, IMO.

-- Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton

there are several sealants made…but the best i have ever found is using BIN primer sealer…it is a white shellac base, several coats and give it a good scuff sand with some 320 and you are good to go…works well…as well shellac in about a 3 lb cut does well…

SHELLAC is awesome for sealing mdf and easy to apply. I have used all kinds of fillers and muds and pastes and other junk I had heard of but shellac is hands down the best solution. In fact I’m about to use it on some cabinet doors I’m building for a client. GOOD LUCK!!!!!

-- Jed,Ala,jmwoodworks057.com