Sealer for MDF

[Mick4412]

Just finished a CD unit for a family member, who, to reduce costs,asked me to use MDF. As it was for a temporary apartment they were renting , I agreed.
Finished unit, all pieces thoroughly sanded to 320 grit before joining, and sprayed with your El-cheapo paint cans. Four coats later, sanding lightly after each application, the MDF was still absorbing the paint ( or maybe, some paint and whatever was in the can) . I then hand painted it with some decent paint - they are happy, but to me, the job looked S***house
Had it been for something more permanent, I would have stared again.
Did a search of the BB, some suggest sealing MDF with a shellac/talcom powder mix.
1) Any one done this
2) What is a suitable mix of shellac & talc
thanks
mick

[Gumby]

I haven't done it but I wonder if that wall board undercoat/sealer would be a good option as a first coat.

2nd option - lots of paint

[ernknot]

Concrete is pretty good! MDF has to be the worst crap since asbestos. Avoid it at all costs.

[Shane Watson]

HAvn't done it, but you should have tried sealing with a can of the el-cheapo undercoat first, that would have helped.

[outback]

I'm happy to be proven wrong, however I think you'll find that the talc/shellac combo is for sealing grain, prior to french polishing.

Straight shellac oughta help seal the mdf.

I reckon good sealing paint is the go though.

[graemet]

When I HAVE to use MDF, I use Dulux acrylic sealer/undercoat, let it dry for an hour or two and sand it back. If there are any bare patches, another coat, then one or (max) two top coats are sufficient. Saves loads of time and paint.
Cheers
Graeme

[Harry72]

Use some fibre glass resin on the edges to stop them from soaking up the paint. If you coat the whole lot it'll make it water proof!

[maglite]

I used the MDF sealer made by Whiteknight Paints.......it worked pretty well but seemed to me that is was ordinary acrylic sealer/undercoat with most of the water sucked out.

[custos]

When I HAVE to use MDF, I use Dulux acrylic sealer/undercoat, let it dry for an hour or two and sand it back. If there are any bare patches, another coat, then one or (max) two top coats are sufficient. Saves loads of time and paint.

Ditto. I use it for drawer bottoms and Dulux undercoat sealer followed by a light sand and whatever finish coat you like works fine. Actually, it's pretty common to use MDF for skirting boards and window frames these days because you can get a good smooth finish. Typically you would give it two undercoats (water based undercoat/sealer) followed by a gloss finish.