Painting over pre-painted MDF

[Tinkjon]

I've got an old MDF dressing table that is painted - I'm not sure what the paint is, it's neither matt nor gloss but has a very slight sheen to it. I want to paint over this, preferably with gloss paint. Can I just lightly sand the paint and go straight over it with the gloss or do I need to do anything first? Presuming that I don't need MDF primer as it's already painted?

Thanks!

 

[stevewestern]

My feeling is to wash it down to remove any polish or grease, then sand down to key the surface. Then I would use a primer like zinsser coverstain or 123 which will ensure the new paint bonds to the old.
Then my choice would be something like Johnstones Aqua undercoat and 2 coats of gloss - this is waterbased so dries fast, doesn't yellow and is very food. A splash of water will help reduce brush marks but even better is some Floetrol as this helps the paint level off and keeps a wet edge for longer. If the room is warm then but some damp cloths on the radiator to increase the humidity - this too will help.

If you don't use a primer you MAY find the top coat doesn't bond well, and either way a coat of gloss really needs an undercoat but you may find the zinsser primer will suffice so no undercoat is needed.

Since 2010 oil based paints have lower levels of all the stuff that made it dry well, and it yellows quickly - however, it won't kill you as fast. It can take a long time to dry properly so many have turned to water based paint.

It sounds like the old paint is an eggshell from the way you describe it.

Hope this is of some help even if a bit long winded !

 

[Tinkjon]

That's great, Steve - many thanks! I have got some Zinsser BIN in the cupboard - would that do instead of the Coverstain?

 

[stevewestern]

I am not sure if bin would be ideal but guess it would do. However it is hard to paint and getting a decent finish would be hard plus it stinks. Another thing to think about is a decent brush...