Medium-density fiberboard, or MDF, is a building component used for so many things in the home: kitchen cabinets, bathroom vanities, bookshelves, baseboards, interior doors, nightstands—the list goes on. With so many pieces made of MDF, it follows that they will eventually wear down and become chipped, dingy, or just dated-looking.
Fortunately, you can paint MDF and bring these pieces back to life. You can even build new cabinets, shelves, and furniture from MDF and paint them—resulting in a smooth, glass-like finish.
Before You Begin
With its porous surface and flaky edges, MDF may not seem like a good candidate for a successful paint job. It's true that paint applied directly to MDF can cause the surface to become swollen and distorted. Edges siphon up paint, no matter how much paint you apply.
But by treating the MDF with conditioner products first, you can paint MDF just like you would other, less-porous surfaces.
The large, flat surfaces of MDF are easier to paint than the edges because the compressed wood fibers form a tighter bond across the surface. It needs less sealing. Plus, you shouldn't encounter large pits on the surface.
Use a one-step clear sanding sealer to condition the MDF before painting. Oil-based sanding sealers work well, but you can also use a water-based sanding sealer if you prefer.
The edges of MDF can be conditioned with the same sanding sealer as you used for the surfaces. Because the edges are so porous, you'll still need to apply multiple coats of sanding sealer and sand between each coat.
A better method is to fill the edges with an acrylic polymer-based filler. This filler requires only one or two applications and it takes care of the large pits that you sometimes encounter in MDF edges.
Always work in a well-ventilated area when using paints, fillers, or coatings. Wear latex gloves. When sanding, use breathing protection.
Equipment / Tools
- Roller and foam roller covers
- Putty knife
- Sanding block
- Tack cloth
- Sanding sealer
- Polymer-based filler
- Paint tray and liners
Sand Surface and Edges
With #220 grit sandpaper on a sanding block, lightly sand the surface. If the 90-degree edges are bumpy or flaky, carefully sand those down as well. Your goal is to remove any wax coating and knock down any high spots or other anomalies rather than to achieve a smooth surface. Sanding uncoated MDF too hard will abrade it and make it more difficult to seal and paint.
Apply Sanding Sealer
Stir the sanding sealer to mix. Pour the product into a lined paint tray. Roll the product onto the surface.
Let the sanding sealer dry for at least one hour. The sanding sealer likely has raised the surface of the MDF. With #220 grit sandpaper on the oscillating sander, sand the surface of the MDF smooth. Be careful not to sand through the sanding sealer.
Clean MDF Surface
Clean off the surface of the MDF first with a shop vacuum, then with a tack cloth.
Apply Second Coat of Sealer
Roll on the second coat of sanding sealer, just as you did with the first coat.
Sand Second Coat of Sealer
After letting the second coat of sealer dry for at least one hour, sand the surface a second time. Since the surface should not be raised any longer, you should be able to switch to the finer grit #320 sandpaper.
Apply Filler to Edges
With the putty knife, apply the filler to the edges of the MDF. Press the filler deeply into the holes and cracks. Let dry for two to three hours.
Another way to apply filler to MDF edges is to rub it on with a finger. This application method is messier, so you'll need to do more sanding of the MDF to get rid of ridges.
Sand and Apply Second Filler Coat
By hand, lightly sand the edges of the MDF with #220 sandpaper. Wipe down with a dry cloth. Add a second coat of filler. Let this second coat of filler dry longer—about four hours.
Sand the second coat of edge filler with #320 grit sandpaper. Move the sandpaper to the surface of the MDF again and sand that, as well. Pay special attention to the 90-degree angle between the edge and the surface.
Wipe down the MDF with a tack cloth. Apply paint to the MDF by rolling, brushing, or spraying. Allow for about an hour between recoats. Recoat two or three times, if needed.
Tips For Painting MDF
- When applying edge filler, you can round the edges if you wish. Simply bulk up the filler to about 1/4 inch, then sculpt it to a rounded contour by hand with sandpaper.
- Sanding sealer and polymer filler soak up paint at slightly different rates. To equalize, apply a thin layer of primer to the edges before painting.
- Avoid using drywall compound as an edge filler. Use only a polymer-enhanced product for greater strength.
- Sealed and filled MDF cannot be stained. It can only be painted.