visionset wrote:
In the archives this subject is pretty well covered.
It seems an equal spilt between water and oil based primers.
My inclination would be to opt for oil based.
We all know MDF swells after water contact, so for that reason I'd not go
for water based.
This is to prime the bit of mdf that I've exposed by routing another profile
over an old one, on some skirting that'll eventually get white gloss.


I've built loads of (kitchen) projects with MDF. I use this formula to
paint them: One coat of water-based wood primer (cheap as possible -
B&Q's is OK), then rub down with 120 grit, pay attention to the edges
and routed features - maybe reprime if the rub down exposes too much.
Undercoat appropriate for the top coat colour as recommended by the top
coat manufacturer, rub down with 320 grit. First top coat, rub down with
400 grit with a hand block, then the final top coat. The result looks,
and feels, like gloss melamine.

If there are holes to cut, say for hinges, I cut them first, so that the
primer gets into them too.

What matters is a complete film of water-proof paint over the whole
piece, not what the solvent is.

R.