Best Way To Seal MDF?

[Jerome]

It has been 4 weeks since I ordered my PRS alpha. They said it would be 5 weeks so I am hoping to hear something this week. Now for the question

I picked up some Trupan for the bleeder board. I plan to us regular MDF for the vacuum plenum. Has anyone ever used Thompson's Water Seal for sealing the MDF?

If not, what would you suggest.

Thank You
Jerome

[cabnet636]

i would think thompsons would be too thin and cause some swelling, i shot mine with sanding sealer/ sanded a bit/ finished with a clear acrylic, two yeas old and seems to have worked well

[dlcw]

I used two layers of 3/4" baltic birch for my plenum and sealed it with 4 coats of shellac. Works really well. I'm at 2500 foot altitude and pull 8 inches of vacuum.

[knight_toolworks]

the fastest method is yellow glue thinned a bit. it will dry very fast as it does not soak in deep lt does not stink is dirt cheap and it usually does the job in one coat.

[garyb]

I'm with Don, the shellac is hard to beat
Gary

[Gary Campbell]

I agree with Don & Gary. I used lacquer sanding sealer on one and the last had 3 coats of urethane. I never put water based product on wood. MDF swells from the moisture in the glue at a glue joint, I would be hard pressed to cover a large area with it.

[knight_toolworks]

of course it will swell but then it will shrink and it is not a problem. I did the last one with just a 3" paintbrush and went at it. not a big deal I let it dry overnight.
I laminated mdf all the time and it is not an issue. I know a guy who builds nice furniture out of mdf with 45 mitered corners and never has an issue.
I just replaced my spoilboard I sealed the edges with yellow glue 30 minutes later I am up and running.

[gundog]

I used fiberglass resin to seal my MDF plenum I would never do it again. The finished product came out OK but the fumes where awful never again.

Mike

[cip]

My last two plenum boards have been with Extira. It's water proof, won't swell, cuts easy and no sealing because it's made with resin glue and is as close to air tight as needed. Why waste time sealing when the product does it automatically?

Trupan is good for a spoil board because it's a little more open then regular MDF and allows more vacuum to the surface but you must seal the edges well.

Mike

[Jerome]

Thank You for the advice
Looks like water seal is out (I had some left over and was trying to save a few bucks)

It looks like the sanding sealer and shellac have the most votes.

Thanks again

[wberminio]

Jerome

Your best bet would be to seal with shellac or sanding sealer and top coating with a lacquer or varnish.The shellac will seal the porous MDF and the top coat will give added protection from moisture.

[harryball]

Shellac, but let the first coat dry very well. I found if you recoat too soon it softens the first coat again. I use the amber shellac, cheaper than clear, at least it is here.

/RB