Sealing MDF

I've just bought a cheap bench - all fine except it has untreated a 5mm MDF shelf and top.

As it's in the cellar, which isn't bone dry, I thought it best to seal it. I've got some PVA (just normal evostick, not the waterproof variety)

- would a watered down version of that work?

A google search suggests that it might not - contact with moisture would make it return to liquid, or somesuch, and to use specialist MDF sealant. But a lot of differing opinions.

Reply to
RJH
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On a woodwork forum they advised wax it then 2 coats of polyurethane ... I questioned applying PU over wax and they confirmed that was the correct approach.

Reply to
rick

RJH laid this down on his screen :

5mm for a workbench?
Reply to
Harry Bloomfield

Just what I was thinking!

Reply to
Davidm

PVA is water soluble, and mold will love it.

Even EVA (waterproof PVA) is water soluble - it's only waterproof when used in cement mortar mixes (although SBR is even better for that).

Whilst you can use something like wax or polyurethane to provide some surface protection against an occasional spill, nothing will protect it against long term high humidity. You'll need to make a new piece when it decays. Plywood would last longer.

Reply to
Andrew Gabriel

I can see why you queried it. Are you sure they weren't pulling your leg? :)

Seriously, does the wax sink in, or how does it work?

Reply to
GB

My feeling would be that, unless it is *really* wet, the OP would be much better leaving the MDF untreated. It would then be able to dry out to an extent rather than having the damp sealed in. I.e. like a house, good drainage and ventilation, not hermetically sealed.

Reply to
Chris Green

Yes, surely not. But if it is, just plonk some 18 mm shuttering ply on top of it. Plus a few coats of polyurethane on top if you want to be smart.

Reply to
newshound

But they were still wrong. TW

Reply to
TimW

Ah, hadn't known that, thanks.

Many thanks Chris and everyone.

I think I might leave it. The cellar floor might become damp a few times each year, but I've stored wood down there for years with no apparent ill-effect.

It was just the blotting paperyness of mdf that had me thinking, together with the 5mm.

On which, it really is surprisingly sturdy - it's one of these:

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I bought it for storage/light use, but it's strong enough to support a vice once I've added some leftover kitchen worktop.

Reply to
RJH

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