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I recently bought a workbench with a 900x1500x12mm MDF top and it doesn't appear to be sealed.

What should I apply to seal the edges from leaking and seal the top from absorbing? Indoor use, subject to humidity.

I've been told and read many contradicting advice from being paint ready, requiring primer, do and don't use oil/water based products. None of which have managed to instil any confidence in their advice.

I don't care what it looks like, I just want it to not leak glue fumes and resist humidity/light spillages. Preferably for cheap and without requiring sanding.

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What should I apply to seal the edges from leaking and seal the top from absorbing? Indoor use, subject to humidity.

Technically you don't have to do anything to it, many people have MDF benchtops with no finish on them. The moisture in the air is basically a non-issue for MDF, it's only liquid water that you need to be concerned with.

On a separate durability issue however, the edges of MDF are fairly friable and prone to damage. If you're OK with your bench taking its licks and showing it that's fine, use it as-is. But many people edge their MDF benchtops with strips of wood (hardwood or softwood, your preference):

MDF workbench tops

As I think you can see the MDF in these benches appears to be without a finish.

In addition to adding durability to knocks and scrapes solid wood edging strips effectively cover the cut edges of the MDF and hence add quite a bit of water-resistance at the same time.

light spillages

If you do expect you'll spill water on the bench then it is a good idea to apply a finish. Many people use a traditional workbench finish: a couple of coats of oil (usually BLO or tung oil), but you'll be better off if you use varnish as it is far more waterproofing (and the MDF far more prone to damage from water than the traditional solid wood).

Dilute at least the first couple of coats of your varnish by about 1:1 with added spirits to improve penetration, then two full-strength coats if you want very high levels of water-resistance.

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I always wear a mask when I cut it. I would sand it myself so it would adhere better but you don't have to it just won't look as good. I myself wouldn't paint it as the MDF will stay flat without finishing because it's got all that glue holding it together. I have pieces unfinished laying around for years and it's fine.

Some say the formaldehyde is safe and can't leak because of the glue it is in case in. I won't go into that but it is better to be safe then sorry.

  • Yeah, I'm not sure why there would be any issues if you aren't cutting it. – Raystafarian Sep 11 '15 at 17:43
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The simplest finish is to apply a coat or two of paste wax. I have an assembly bench with a MDF top which I have treated with paste wax and the wax is very good at repelling wood glues and water. It requires a fresh coat of wax every year or so.

  • Wax is great for shrugging off glue but in thin layers is doesn't do much against water. The beading on the surface that you can get is misleading, it's actually very poor at resisting the penetration of water. – Graphus supports Monica Feb 17 '16 at 10:47

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