Picture framing

Black emulsion.

That's an interesting idea, I'd expected the MDF to be too porous for emulsion but will experiment - have you actually tried it?

Emulsion onto MDF? Yes - many times. Very successful even without using special MDF primers. Just takes several coats (which I usually apply with a roller). I have almost always applied a topcoat of some water-based lacquer/varnish.

Black emulsion onto routed MDF? No. I'd experiment. :-)

Not much on MDF per se, but on various other surfaces, mainly for theatrical sets. Primer on MDF might help to reduce uneven absorption.

Actually you might think that theatres would go for MDF in a big way - however stage floors are often covered in good old-fashioned hardboard (usually partially or wholly covered with carpet/mats), 'flats' (sort of sections of wall surface) are normally of plywood (it's an acoustic thing) , and there's still a lot of _real_ wood used for doors, window frames et. al.

You might have to go to a real paint store to get black emulsion - I can't say I've really noticed it in the sheds (although I haven't searched for it in such establishments - we have an account with a proper locally-based (no pun intended!) paint merchant).

I've emulsioned MDF many times with good results. Never black though.

Is your theory that absorption will vary on the routed/un routed surfaces? I think you may have a point. The cut edges of MDF do absorb more paint than the smooth faces thats for sure. Black might well show up more?

Er! chalk board paint

Someone suggested black emulsion this will gather dust in no time so I would think its best to use an emulsion as a primer and a semi gloss(Satin Black)as the finishing touch.

No such thing as black emulsion paint. At best it comes out dark grey. You really need an oil based paint for true black. Painting the mdf moulding with a slurry of filler, and rubbing down when dry should make the suction uniform

Shouldn't you be informing MrErskine that not me? I have suggested elsewhere Chalkboard black paint which dries matt. ;-)

Exactly so - may even cause slight swelling of the MDF - this has not been obvious when just doing cut edges, but a larger section might absorb more water and so be more prone to swelling.

You can buy black mouldings from here :-