Paint 3D printed models: Here’s how

I recently acquired a 3D printed door for my Commodore 1084 monitor. It was missing its original. Of course, it came in white. I can live without an imperfect match, but I want something closer than white. But can you paint 3D printed objects? Yes you can. Here’s how to paint 3D printed models.

Plastic can be tricky to paint, but 3D prints tend to have some texture, and that makes it easier for paint to bond to them than molded plastic. Still, some prep work is still a good idea.

Good painting begins with good preparation

paint 3d print
I painted this 3D printed monitor door for a Commodore monitor with general purpose Krylon spray paint. I painted it outdoors and used the box the model shipped in for support.

Because of the way 3D printers work, 3D prints tend to have a bit of a crosshatch pattern in the surface. You can sand this if you want a smoother finish. But that crosshatch surface gives the paint something to cling to, so it’s perfectly OK to leave it. If you sand it, that’s OK too, because the sanded surface will still be rough enough for paint to grip.

Even if you don’t sand it, wipe down the surface with some mineral spirits. Alcohol will work if you don’t have any mineral spirits, but I find mineral spirits work better and faster. You want to eliminate any dirt and oil on the surface, and mineral spirits make quick work of that. Give it about five minutes to dry, and the 3D model is ready to paint.

Spray paint a 3D print

paint 3D printed model
Here’s my painted 3D printed monitor door, installed on my Commodore 1084S monitor. The match isn’t quite perfect, but it’s much better than white.

I decided to use spray paint. I definitely wanted an oil-based paint for durability. I’m going to open this door occasionally, so I need something that can give the corrosive oils from my hands a bit of a fight.

The best paint to use is a paint that bonds to plastic, such as Krylon Fusion. Those paints fuse to the plastic and create a nearly permanent bond. The only trouble is the color selection. If Krylon has the color you want, fantastic. Use it. If they don’t have the color you want, I’m not surprised.

If you have to use a general-purpose paint, use a primer first. I know a lot of paint says it’s paint and primer in one. Use a dedicated primer anyway. You’ll get better results. Spray a thin coat of primer onto the model and let it dry according to the instructions. A thin coat dries faster. It’s OK if it just barely covers. Its job is just to stick and give the paint an optimal surface to stick to.

When the primer is dry, spray a coat of the paint you want. Be sure to shake the can thoroughly. I have some tips for shaking paint cans and applying paint. I like to apply thin coats about an hour apart until I get the coverage I want. The instructions on the can will tell you how long you have to wait between coats. You get better results with multiple thin coats than with 1-2 thick coats.

Let it dry, ideally outdoors in 70 degree heat or higher. If it’s much colder than that, take it indoors to dry.

And that’s really about all there is to it.

Do you have to match brands of paint and primer?

If you want to be really safe, use the same brand of paint and primer. If you can’t do that, just be ready to test on something else before you paint your 3D model that way. Make sure the two don’t fight.

Paint formulations do change over time, so be sure to try it out, even if it worked last time.

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