BLO on MDF--How much is enough (or too much)?

[Dan Case LR]

I'm finishing my new bench top with BLO. The top is three layers of 3/4 MDF with a maple skirt.

Several of the resources I've seen for using BLO say to apply multiple coats until the wood won't absorb any more. I've done three coats and the Maple seems to have had enough (no surprise), but the MDF just keeps sucking it in (not a surprise either). I know the MDF will be thirsty, but I find myself wondering if continuing to add oil to it is counter-productive. I did a third coat last night, and when I went back to wipe it off the MDF had sucked it all in. This morning, I put another coat on just the MDF, slathering it on thicker than usual, and an hour later the MDF was as dry again.

I worry that continuing to support this bench top's drinking habit might land it in a skid row drunk tank.

Should I call it done, or keep adding BLO until it's had enough?

D.

[Jamie Buxton]

I'll bet the MDF can suck up a huge amount of oil. You might consider sealing it with varnish, or with a varnish-BLO blend.

[Prashun Patel]

The problem with it drinking so much is that it can take forever to dry properly. I would first give it some time to dry as is. After this, I would switch to an oil/varnish blend. It will do a better job of sealing the porous mdf.

[Bill White]

No BLO on MDF. That stuff is like a blotter, and too much will cause it to swell. I just use shellac on MDF as a sealer. Then, add whatever finish you choose.
All that being said, there is an exterior grade MDF (Extira) that is not as "hungry".
Bill

[John Coloccia]

In my opinion, spar varnish is a much better choice on a utility piece made out of MDF.

[Matt Mackinnon]

I used a water based varithain on mine. It took in about 3 coats and now is rock hard.

[David Helm]

No BLO on MDF. That stuff is like a blotter, and too much will cause it to swell. I just use shellac on MDF as a sealer. Then, add whatever finish you choose.
All that being said, there is an exterior grade MDF (Extira) that is not as "hungry".
Bill

+ 1 on the swelling. You'll never be able to reflatten the mdf.

[glenn bradley]

I mixed BLO with Mineral Spirits 1:1 and rolled it on with a little disposable roller. At first there were stripes where I rolled but, the MDF absorbed and spread the BLO till the appearance was even. I left it at that. The flooding technique where you give it till no more will soak is is used for hardwoods. I was confused by the post in your other thread where someone said MDF would not soak up BLO like other woods(?). Obviously you see, as I did, that it will soak it up like a sponge if you let it. I would say you have plenty already. If you keep adding it you will end up with a hump in the middle of your top :D.

[Dan Case LR]

Fortunately, knowing the sponge-like qualities of MDF, I haven't flooded it, just applied three or four good wipe-on coats, mostly a day apart. I'll give it another day or two and then decide if I want to leave it as-is or hit it with a little varnish.

I'd read somewhere that if you let the first coat of BLO on MDF cure well it will help prevent subsequent coats from over-absorbing. Go figure.

D.