How to Paint MDF
Achieving a Smooth Finish in 10 Easy Steps
Medium-density fiberboard (MDF) is a building component used for items in the home, like kitchen cabinets, bathroom vanities, bookshelves, baseboards, interior doors, and nightstands. With so many uses for MDF, cabinets and furniture will eventually wear down and become chipped, dingy, or dated-looking. Still, you can re-paint MDF professionally, even as a DIY, by following a few careful steps.
First, to get a smooth paint finish on MDF, you'll need to lightly sand it. Then, seal the MDF before painting with primer to assure a smooth finish. Even if you build brand-new cabinets, shelves, and furniture from MDF, you can still use the same protocol—resulting in a professional finish without the contractor pricing.
Before You Begin
Painting MDF cabinets is not as straightforward as you may think. The product's porosity can result in a rough, swollen, or distorted surface texture after painting. Also, the edges of the MDF tend to siphon up paint, no matter how much is applied.
By first treating the MDF with a conditioning product, like a primer, you can paint MDF just like you would a less-porous surface. The type of paint you use on MDF is also important. Oil-based paints will help you achieve the smooth finish you're looking for. Water-based paints, on the other hand, are not suited for porous MDF, even after its sealed.
Finally, for a smooth finish, it is best to paint large surfaces of MDF with a roller. A foam roller, specifically, will give MDF the smoothest finish.
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.
What You'll Need
Equipment / Tools
- Roller and foam roller covers
- Putty knife
- Sanding block
- Tack cloth
- Oscillating sander (optional)
- Sanding sealer
- Polymer-based filler
- Paint tray and liners
- #220 and #320 sandpaper
How to Paint MDF
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 sanding block or 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.
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.
Why is MDF rough after painting?
Both normal and moisture-resistant MDF will become rough on the edges after painting, as the paint will raise the wood fiber grains.
Is one coat of primer enough on MDF?
Since MDF is a super absorbent material, it is necessary to add two coats of primer before a coat of paint. Sand the edges lightly in between the primer and the paint to take away the roughness.
Can you paint over MDF without sanding?
MDF comes pre-sanded, however, a light sanding with fine-grade sandpaper will help the primer and paint adhesion.