6 / 10
Sand, Prime, Sand
The face of MDF is smooth, but the edges are fuzzy like the skin of a peach. If you just slap paint on the fuzz, it will look and feel like sandpaper. So you have to get rid of the peach fuzz before you paint. I have two recipes for smooth edges: one for “good-enough” edges and the other for edges that will get a high-gloss finish.
Here’s the good-enough process I apply to most projects, including trim: First, lightly sand the edges with 100-grit paper. Foam-backed sanding pads work great on routed profiles. Then prime the MDF. Use a solvent-based primer only. Water-based primer can raise small blisters. My favorite MDF primers are KILZ and Cover Stain because they’re easy to sand. When the primer dries, sand off the fuzz with 100-grit pads.
A couple of light passes is all it takes. You can sand KILZ or Cover Stain after a couple of hours, but let the primer dry overnight for smoother results. After sanding, wipe away the powdery dust with a damp cloth and you’re ready to paint.
7 / 10
Don’t Drop It
The face of MDF is harder than most woods, but the inner layers are soft. So edges, and especially corners, are easy to crush. That means you have to handle it with more care than lumber or plywood. Also, avoid scratching the face. Light scratches stand out like a sore thumb on the ultra-smooth surface, so you have to sand them out completely before priming.
And wear gloves when handling MDF wood, especially when carrying heavy sheets. MDF edges can be sharp enough to cut skin—I’ve got the scars to prove it.
8 / 10
Don’t Let It Get Wet
MDF stands up to moisture about as well as graham crackers. A few water drops will raise small bumps on the surface. A long soaking will make it swell to twice its original thickness. So MDF is a risky choice for baseboards in entryways and trim near tubs or sinks. My all-time greatest MDF mistake was using it for windowsills in my own home.
If you use MDF as baseboard, be sure to paint the lower edge before installation. That will provide short-term protection against occasional spills. Also install the baseboard about 1/4 in. above the floor and then cover the gap with wood base shoe molding. There are moisture-resistant versions of MDF, but they’re hard to find. To find manufacturers and dealers, search online for “moisture resistant MDF.”
ncG1vNJzZmivp6x7p63MoqOyoJGjsbq5wKdlnKedZLmqv9Noq6Koo2KzsL6MrqqippdiuqWyjLCmqJxf