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When I'm designing for my laser cutter, I actually like using MDF (medium density fiberboard) quite a bit. I like it because it's inexpesnive and easy to work with, but it doesn't always get the best finish when I paint it. Well, I've figured out how the get the best finish on your MDF projects!
I'm a huge fan of spray paint for stuff like this; it's quick, it's easy, it looks great. It comes in a million colors too, so I've amassed quite a collection. (Just ask my husband. Every time we walk into Ace or Home Depot, I tell him “I need spray paint!”)
While it's got all these things going for it, it's also not always the best finished product when you're working with MDF.
I've basically managed to cross off a bunch of the “MDF Cons” list with just one product! Sanding Sealer.
I hit my material with a coat of this before painting, and it‘s a whole new painting exeprience! Because I work with lasers, I have also included those pesky edges in my testing, so you'll see those.
NOTE: I mistyped on my sample file; where it says “sanding primer” or “primer” it should say “sanding sealer” or “sealer” Oops.
So I think this chart is pretty self-explanatory, but I'll explain it anyway. You can see what the plain MDF looks like on the left, and then with the Sanding Primer on the far right.
The sanding sealer goes on very watery. I used a sponge brush and it worked great. A little bit goes a long way, so keep that in mind! (Also that can seems expensive, but it'll last forever!)
Just a light coat on your MDF, and then give it a bit of time to dry.
The samples below show the difference between a single coat spray paint on untreated, two coats on untreated, and one coast on untreated.
The other part I was really curious about was painting the actual laser cut edges of the material; the char on those edges can be really tough to paint, so I wanted to see if I could get decent results here. Personally, I'm a fan of the black edges with a painted top, and I often paint before I even cut, so this isn't really a big concern for me, but I know some people prefer a painted edge.
The edge samples before painting; the first three are my standard 1/8″ MDF settings for the “light” edge” The dark one (#4) I ran much slower to intentionally get more char than ususal. The last one was sanded after gluing, as you can see. This isn't a very logical solution for some more ornate cuts, like script lettering, but I wanted to include it here.
As you can see, there are some pretty pronounced differences here. (Ignore the glue smears! I used CA glue, which clearly paints pretty well lol)
There's not a dramatic difference between the light and dark edges, but the sealed MDF is certainly more evenly covered!
I hope this was helpful, and please feel free to leave a comment if you have a question or would like to see any more future tutorials! In the meantime, be sure to check out all my laser-related content, including stuff for Glowforge and Aeon Mira owners!
Claudia M Cadzow says
Are you masking the mdf after using the sealer and paint? Any help is appreciated
I don’t often mask, but I’m running a Mira9 with an external compressor. On the Glowforge, I would recommend masking. You’ll find masking will stick better after a couple of days for the paint to cure.
Derek Fulmer says
Very helpful article. I am using CNC-cut MDF for projects lately and I have been using 3-4 coats of spray. I will give this a shot! Thanks again!
Marion Ferguson says
I have been spray finishing wood and many other products for 75 years, yes I am old (89 actually).
I hate rattle cans but sometimes you need to use them.
Many of the sanding sealers are water based these days unfortunately solvent based sealer do a better job.
Laser engraving over a finished piece of wood product solid or MDF requires some R&R as you have found. Cutting is a whole new experience. Be very careful what you use as a finish some can be very detrimental to you and your laser.
Most standard finishes are laser safe once cured, the exception is resin/epoxy which should never go in a laser.