Smooth finish on MDF

That rather depends upon *which* stuff. International make a primer that is the best I have ever seen (for your purpose). It was originally formulated to fill the grain on Phillipine mahogany in marine applications...dries fast, sands very easily. Don't recall the ID# but the last time I checked (couple of years) it was running about $80/gal.

-- dadiOH ____________________________

dadiOH's dandies v3.06... ...a help file of info about MP3s, recording from LP/cassette and tips & tricks on this and that. Get it at

The only product I could find here in the UK was "International MDF Primer".

I used it to prime some MDF loudspeakers I built (with a brush). I left the primed boxes for a couple of days (at roughly 68 degrees F and low humidity). When I tried to sand it the primer clogged the paper, and came off in little rolls - basically it hadn't fully dried and was still slightly plastic.

I (tediously) sanded all the primer off with a powered sander, and bought another batch (with a different batch code).

This time I used a roller, then left the boxes in a drying room (around 80F) for a week. Guess what happened when I sanded it again? Yep. Same result.

I did contact International to work out what went wrong. They sent me a catalogue. Thanks.

What was the primer you've seen?

Sploo.

Sorry, but as I said I don't recall the number. Been too long. "International #62" sticks in my mind but I have no idea if that is right or not.

I used to use it a lot when I had a yacht, both on it and other wood projects, but that has been a while back. Nowadays, I just use auto body primer if I want one that sands well.

-- dadiOH ____________________________

dadiOH's dandies v3.06... ...a help file of info about MP3s, recording from LP/cassette and tips & tricks on this and that. Get it at