Updated: Aug 13, 2022
We've all either seen the post from someone else or thought about it ourselves, "What's the best way to paint MDF?" Some crafters make painted products that look as smooth as glass and as evenly colored as a photoshopped headshot. Well everyone, here's my attempt to help you have similar results and if nothing else, help you improve.
First and foremost, I just want to make sure it's known that all MDF is NOT created equally. Some absorb more paint than others, some cut faster, some slower, some leave charred edges, and some don't. With that being said, all tests were performed on our 1/8" MDF and not to be biased, but I think it's the best MDF around.
TEST/Scenario 1: Brushing on Acrylic Paints
I saw a guy about two months ago perform a test in which he painted and compared how well sanded MDF vs UNSANDED MDF looked. His results showed that the SANDED MDF was better in appearance than the UNSANDED MDF. His reasoning was that when sanded with 220 and then 400 grit sand paper, the pores of the MDF were basically closed preventing most of the paint from being absorbed. In his case, the results did show a big difference.
I decided to test this process on our MDF using acrylic paint from Walmart (spray paint may yield different results). Below are the photos of my test.
I tested both with 1 coat of acrylic paint (Apple Barrel) and 2 coats.
Conclusion: In regards to our MDF, sanding did NOT affect paint absorption. Our MDF had very similar results for all of the tests, making "painting raw MDF" the better option in this scenario. Results may vary with other brands.
Test/ Scenario 2: Using Spray Paint to Achieve a Picture Perfect Finish
So I've seen many recommendations on how to achieve ultra smooth, even finishes on painted MDF projects. In this test, I tried 5 different methods of painting a project using spray paint.
-5 different methods all using just 1 coat of spray paint.
-All sanding was done using 220 grit sandpaper on a random orbital sander. One quick pass over the entire sheet lengthwise and one pass along the width.
Applied one coat of spray paint to raw MDF
Applied one coat of sanding sealer with foam brush, sanded after 30 mins, applied 1 coat of Spray paint
Applied one coat of flat white paint/primer, after 24 hours sanded, then applied 1 coat of spray paint
Applied one coat of filler primer, after 24 hours sanded, then applied 1 coat of spray paint
Applied two coats of Zinsser (according to directions), sanded after 24 hours, then applied 1 coat of spray paint
The photos don't really do the test any justice. In my opinion, the Zinsser gave the most glass like finish. I'd like to run another test with it and just sand it a little more.
The Flat paint and the Filler primer gave pretty much identical results. The were both really smooth and had an even color while showing the sheen of the paint.
The sanding sealer did pretty well also. Definitely a satisfactory finish. It didn't do great in showing the satin finish.
The raw MDF was my least favorite of the group. It did absorb some and the sprayed texture/MDF could be felt. I'd image that a second coat would help a lot or maybe even a clear coat.
All in all, I'll say this:
Fastest Good Finish = Sanding Sealer
Glass Like Finish(slower) = Zinsser (I'll run another test soon)
All-Around Great Finish=Flat White or Grey Filler Primer
As for spray painting raw MDF, it's definitely an option. Further testing is needed to see if the application of a clear coat improves the smoothness and evenness of color.
Hopefully, these test and tips help you have success. If you have any questions, please feel free to reach out to us.