How do you "edge seal" your MDF enclosures?

[The Paulinator]

I've heard of people using wood glue, but that seems to be alot more of a hassle than it needs to be. Does anybody have any tips? I try to do it with watered-down wood filler, which seems to work ok, but I don't know if that's the difinitive way to do it or not.

[Cloth Ears]

Do you mean sealing the cut edge of the MDF where it's exposed to the 'outside world'? Or sealing the edges where they join to other pieces of MDF?

For the first, I veneer, using thick veneer and glue so there's nothing exposed.

For the second, I don't have any gaps to seal.

[jackinnj]

you need a filler which will shrink and expand at the same rate as the MDF -- apply a good sanding sealer, dry per instructions, wet sand, apply another coat, then finish. Zinser works reasonable well.

You can also coat the edges with bondo diluted in a polar organic solvent.

[mlammert]

I have not tried this before, but the magazine - The Family Handyman - had an article about using (I beleive watered down) drywall compound to do this...

Good luck,
Mark

[jackinnj]

Originally posted by mlammert
I have not tried this before, but the magazine - The Family Handyman - had an article about using (I beleive watered down) drywall compound to do this...

Good luck,
Mark

that stuff will fissure -- cracks --

[GM]

Greets!

Drywall joint compound or spackling paste is my filler of choice when it's going to be painted or veneered. For more durability, two part epoxy. In some cases, depending on the finish you want to achieve, a product like gesso is applied and then sanded smooth to fill and seal in the MDF: http://en.wikipedia.org/wiki/Gesso It's used both as sealer and a primer. In other cases a thinned wash coat or two of Shellac or similar. Glue sizing (equal parts white glue and water) can also be used for toners, stains, shading stains, glazes, sealers.

GM

[AIA]

The process is called "glue sizing." Dilute yellow PVA wood glue with tap water (or spike tap water with yellow glue) until it is the consistancy of chicken noodle soup without the chicken and noodles. Brush the mixutre on and let dry. It will seal the very porous edge of MDF so that the edge will take paint the same way the face will take paint.

[pinkmouse]

I'll go with Jack, Sanding sealer is the stuff.

[Curmudgeon]

If you mean an exposed edge, I'm in the veneer camp. Iron on, precut to width type is handy.

For a joint; the new polyurethane glues, of which Gorilla is best known, expand as they cure, ensuring an airtight seam.

[Cloth Ears]

Originally posted by Curmudgeon
For a joint; the new polyurethane glues, of which Gorilla is best known, expand as they cure, ensuring an airtight seam.

That's what I use for edge joints. So I never need to worry about any extra sealing measures. You gotta have pretty good clamps, though, as it's fairly agressive in it's expansion. I use the Selleys version of the same thing.