Finishing MDF Doors
Urethane-based paint versus pigmented lacquer for paint-grade doors. August 9, 2004
I am getting ready to finish MDF paint grade cabinet doors. Should I use a urethane based paint or would a pigmented lacquer give me sufficient coverage and durability?
We use pigmented lacquer all the time on MDF with great results. Pay extra attention to the raw edges when priming and sanding because it really soaks it up. I usually prime the raw areas first, then sand lightly. Prime and sand as usual, then two topcoats. When you prime, use as little thinner as possible. The primer will not seal the edges if it is thinned too much.
Rather than priming the edges of MDF, you will find better results 'sizing' them. This is a mixture of wood glue and water at about a 1 to 1 ratio that can be brushed on the MDF edges with a disposable paint brush. This step is done prior to any finishing and will need to be lightly sanded after the mixture sets up. You will need to first remove all machining marks (saw or jointer) before you apply the sizing or else you chance sanding it all away in the process of removing the machining marks. Sizing also works well to seal porous end grain.
We use products specifically for MDF. We have found Campbell makes a product called Clawlock and Chemcraft makes a product called Plastoprimer. We like the Plastoprimer better as it does not shadow when spraying. These products are both catalyzed. Generally two prime coats followed with one topcoat looks great.
You can also use drywall compound to seal the edges. Thin it down just a little, smear it on and sand it smooth, then prime. Works great.