I have an MDF wood mould that I'm going to use for vacuum forming. I was advised that I should seal it with a wood hardener and it would be easy to sand to a very smooth finish. Has anyone had any experience doing this? Any recommended products? I've researched a few, but it seems like they all have mixed reviews for MDF wood. Also, anything water based appears to swell the wood (not desirable since I had the MDF CNC cut for specific dimensions).

Any ideas?

Thanks guys

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Check out my build!
https://www.fiero.nl/forum/Forum3/HTML/000100.html

I always used Fletco Diamond Cote...latex polyurathane....I love the stuff, goes on easy, it works, and cleans up with water (not to sound like a commercial for them)...but it beats the hell out of boat varnish.

We used to use 1 1/2" thick MDF on our vac tables for the machining centers and sealed the unuded top areas and edges with multiple coats of polyurethane, then covered with--duct tape of course. . Took several coats of poly, as it is so porous, but then ya already know that or wouldn't be wanting to use it for vacuforming. Is this by chance part of your new headlight project?
Impatiently waiting....

[This message has been edited by maryjane (edited 01-14-2012).]

Thanks guys.

Yes it is part of my headlight project. I apologize that its taking a while, but one way or another I will be going through with it. At the moment I'm juggling my job in another city and the car being in another location etc etc. Plus this is a learning experience for me and I'm trying to research all options to come out with a product that everyone will be satisfied with.

Is the polyurethane sandable? Would you happen to know how it responds to heat? Any particular brand name to look for? Is the viscosity low enough to brush it on?

Sorry, it's been too long ago. I said "used to use" because I have been out of machining for about 6 years now. Lots of water under the bridge since I left my machinist job in West Texas.

No problem, bump for any other ideas!