MDF top - to seal, or not to seal?

[Bill in Buena Park]

I took inspiration from JoeyGee's outfeed table, and began cutting up an old hollow-core door to build one of my own. My old door was painted and dinged, however, so want to top it with MDF, then edge band it.

My question is - should I try to protect the MDF from moisture/chipping by sealing it with something, or should I just leave it unfinished? If seal, what's the best product? (that would not mess up the smoothness of the MDF surface)

[cabinetman]

You could just leave it bare. If you want to seal it, several applications of waterbase polyurethane (sprayed if you can) would work well. Or if the MDF is 3/4" use it just as a substrate and top it with 1/4" hardboard (tempered Masonite). It's more damage resistant than MDF, its cheap and easily replaceable.

Leave the edge band wood high enough to cover the hardboard. When it gets to the point of needing replacing, just pop in a new one.
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[Uncle Cracker]

If you do seal it, seal both sides so that the moisture barrier is bi-planar. Helps prevent warping in high humidity.

[Bill in Buena Park]

...top it with 1/4" hardboard (tempered Masonite). It's more damage resistant than MDF, its cheap and easily replaceable.

Leave the edge band wood high enough to cover the hardboard. When it gets to the point of needing replacing, just pop in a new one.
.

Mike, I've been playing with the hardboard topper idea as well.. The "cheap" and "easily replaceable" parts are appealing, and think it will be the way I go. Thanks for the input.

[Bill in Buena Park]

If you do seal it, seal both sides so that the moisture barrier is bi-planar. Helps prevent warping in high humidity.

Thanks UC - I think I'll pass on sealing this time, but as I do not use MDF often (some crazy preference for plywood) - if I do seal on future projects, I'll keep this in mind.

...bi-planar...

That is not how I roll.

[JR]

You should apply at least a coat or two of wax, even if you choose to forego a coat of poly. The wax will obviously make the surface slicker, but will also make cleanup of glue and stain much easier.

If your table will be folded up from time to time you'll want to use a thin panel of MDF. 1/8" or 1/4" will work fine and be much lighter to maneuver.

JR

[docrowan]

I recently experimented with a few different sealers including paste wax on MDF and hardboard. A couple of very thin coats of paste wax makes a very cheap, quick, and slick surface on both materials. If you sand down the edges a bit, then apply white glue, let it dry and sand it a bit again, the paste wax does a good job on the edges as well as the surfaces. Only one coat of white glue, I tried two coats and this built up and didn't perform well.