December 22, 2022
A student of mine asked me the other week whether he could paint MDF without primer. Well, I said he could, but if he did not prime it, he would consume more paint than if he had primed it. Moreover, he would have ended up with a not-so-decent finish without a primer.
Of course, Medium Density Fiberboard (MDF) is unlike the ordinary plywood that you would use in woodworking, and it is not easy to paint an MDF. The reason behind this is that the paint would dry quickly on MDF.
Moreover, it can dry unevenly and may appear blotchy. To avoid such unsatisfactory results, you should use special primers made for MDF. Once you’ve primed it with the right primer, you can then paint the MDF utilizing any ordinary paint.
Our Findings: Can You Paint MDF without Primer?
Yes, you can paint MDF wood surfaces directly without primer at all. But you will encounter three significant issues if you paint directly on the unprimed MDF surfaces.
- The MDF wood will absorb lots of paint before filling across the surface evenly. Thus, at least 15%-20% amount of paint is wasted as compared to applying to the primed MDF surface.
- Paint will dry unevenly and appear blotchy on certain surface areas as the paint has been absorbed unevenly.
- The paint dried extremely fast on the unprimed MDF wood surface. You must be very good at handling the painting process.
Solution: The best way to paint MDF without primer is to use oil-based acrylic paint. This type of paint is specifically designed for MDF to prevent MDF from absorbing the paint too much and will provide a smooth finish. It also dries quickly, so you don’t have to wait too long before applying the second coat.
4 Methods to Get A Smooth & Even Finish on MDF Wood Without Primer
Aside from using the primer to come up with a smooth and evenly finish, you can also use undercoat, PVA glue, Shellac, and drywall to achieve sterling results and seal the MDF edges. Below is a short discussion on the following materials you can use on MDF to come up with an excellent finish:
1) Using Undercoat to Seal the MDF Surface
Using an undercoat, you can fill or patch up some minor imperfections on the MDF’s surface to make it look smooth and give it an even color. Once you’ve applied the undercoat on the MDF surface and let it dry, you can apply the topcoat. The undercoat can also help lighten the texture when you want to transition from a darker color to a lighter color.
Before you apply the top coat after painting the MDF surface with an undercoat, sometimes, you need to sand the surface down because undercoats more often create some degree of a build for covering surface imperfections.
2) Using PVA Glue to Seal MDF Edges
You can seal the MDF edges without using a primer, and many people do this. Yet, if you don’t take extra care, you may end up beset with some issues. To avoid such problems, you need to sand down lightly the edges between every coat of glue. There will be instances when the PVA becomes too thick. In such a case, you can’t sand it down properly.
Thus, it will help if you apply the PVA in a thin layer every time you make a pass. In this way, you can always ensure that the PVA is not too thick but even and level across the MDF surface. To ensure that you apply it thinly, you can use a paint roller.
3) Using Shellac to Seal the MDF Edges
The good thing about using Shellac as an alternative to primer is that it leaves a tough layer on the edges when it dries, which can serve as extra protection for your MDF. You can likewise seal the MDF edges using an oil-based primer.
4) Using Drywall Compound to Seal MDF Edges
Another great option to seal MDF edges is by using a drywall compound. As a caveat, it is crucial that you smoothen the drywall over the edges and apply it evenly. Then, let it dry before you sand down the edges of the board.
Differentiating Between Primer and Undercoat
At the onset, it’ll be helpful to differentiate between a primer and an undercoat. Of course, many people think that undercoats and primer are the same. Yet, they are different. You use a primer before painting any unpainted or new surface.
On the other hand, you apply the undercoat paint before you paint a surface that has been already painted before. An undercoat, of course, can be a primer. Yet, it is wrong to refer to a primer as an undercoat.
The reason behind utilizing an undercoat is that you want to create a smooth and uniform surface before applying the topcoats. Thus, the undercoat paint functions as a base paint for topcoats to have a substantial and denser appearance once you apply the topcoats.
The undercoat is perfect for painting wood substrates. Moreover, the undercoat can cover or patch up imperfections on the surface.
On the other hand, primers are for painting untarnished and virgin surfaces, i.e., facets that have not yet undergone painting before. The primer seals and bonds the surface, functioning as an excellent foundation or base layer for the topcoat application.
You can use the primers for painting the interior as well as exterior surfaces of the house. Primers also come in three types: lacquer, latex, and alkyd ones.
If you are going to paint MDF, it will be helpful to apply up to three coats of primer before you even try to apply the topcoat. I will also recommend that you sand the MDF surface lightly in between every coat of primer. Let it dry for an hour before you begin painting again. In this way, you can ensure that the primer has already dried. For an excellent finish, you should prime both sides of the MDF.
Of course, you can always get by without using a primer on the MDF, but you will be consuming more paint in the process. As a caveat, it will be helpful to refrain from using water-based paint until you have completely sealed the MDF surface; otherwise, you will just raise its fibers and ruin everything.
Jason is a 40-year-old woodworker, carpenter and author who have been involved in the woodworking and woodcraft industry with 17 years of experience. He is expertise in technical aspects, woodcraft and furniture building projects.