In this article, I’d like to show a few examples of using 3D printed airbrushing stencils: various masks and paint shields that let you paint all kinds of shapes on the surface of your model.

Even though commercially available stencils are usually not super expensive, if you want to collect a decent arsenal, the costs will add up; you always have to wait for the shipping, only to find out the shape or size is not exactly what you wanted, etc. On the contrary, with a 3D printer, you have total flexibility in creating any unique shape, always available right when you need it.

I must admit it took me some time before the idea of 3D printing airbrush stencils crossed my mind. I don’t know, I guess it’s because the stencils are flat and just barely three-dimensional… 😅 But now, I use them quite regularly. I have a decent cutting plotter at home, so I can create regular stencils from vinyl foil, too.

But I think the 3D-printed ones are actually superior for many use cases – so it’s not really just about a makeshift solution.

By the way, if you are a total beginner and want to start with vector drawing, sketching, and/or 3D modeling, this is an ideal exercise. Drawing the stencils is super easy; converting them to a 3D object is basically just a single command, and printing takes less than one hour. That means in one afternoon, you can create, test, and iterate on a whole set of various shapes.

Of course, the 3D printed stencils have some limitations, too – I’ll mention them as we go along.

All the pics and short videos are mostly taken just from a single chapter from the recently published Prusa Academy course called Airbrush Your 3D Prints: From Basics to Advanced Tricks. It is the last part of the “trilogy” focused on the whole process of painting your 3D prints (together with the 3D Print Postprocessing and the Miniature Painting courses). In this most recent addition, I wanted to share what I have learned over the last 15 years of using an airbrush, mainly as a scale aircraft modeler.

Anyway, let’s briefly describe the process of creating the stencils, and then look at the examples.

Drawing and printing the stencils

Here is a random blotches pattern stencil as an example. I’ll show right in the next paragraph what it is good for. 😉

For drawing the shapes,  you can use any vector drawing editor, for example, Inkscape, which is open source and completely free. You can start from scratch or use a picture of an existing pattern for inspiration. By the way, there is the Trace Bitmap tool, which works reasonably well for converting raster graphics into vectors – well, at least as a usable base for some further editing.

The other option is to draw the pattern as a sketch directly in CAD software, such as Fusion. In particular, I use the Fit Point Splines tool and then pull the green handles to adjust the curves (see the pic above).

In this case, I used both programs: Inkscape first for the basic pattern, then Fusion for some fine-tuning.

To create a printable object, just select the sketch and use the Extrude tool, about 0.40 mm (i.e., two print layers) upward.

💡The suitable thickness depends on the use case: if you want a pliable stencil that is placed right on the surface and/or has to follow a curved shape, use just a single print layer. If you need to hold the stencil a bit above the surface, it needs to be stiffer (2-3 print layers), so it doesn’t flutter when hit by the stream of air from the airbrush.

As you can see, printing the stencil takes just 20 minutes. You can use a 0.25mm nozzle for smaller and more precise shapes; for this stencil, it’s not necessary, though.

Examples of use

For the first example, let’s continue right away with the stencil I have just shown above.

In one of the sample projects in the airbrushing course, I paint a model of the F-302 fighter, from the sci-fi TV series Stargate SG-1.

The point is to show how to break the visual monotony of large, flat surfaces painted in a single color. So, I start with the whole model painted dull gray.

Holding the stencil a bit above the surface, I airbrush the whole model with lightly diffused black blotches. I also airbrush some freehand black lines along the edges and panels. This method is called the preshading.

I used blue and, later, also yellow, to give the preshading some color variation. One art, please! 🧑‍🎨

Yes, it looks a bit crazy… 😅 But the point comes across soon – when it is overpainted with the intentionally patchy and semi-translucent gray coat. The result is a subtle marbling effect that breaks the solid gray monotony. There is some artistic license, but if you look at pictures of heavily weathered real-world fighter planes such as F-16s or F-18s, it’s actually not that far. In the sample project, I also show other things; there are some weathering effects, rainbow heat staining on the engines, and colorful details for added visual contrast. The picture of the final result is shown further above.⬆️

Symbols and markings

In another sample project of the airbrushing course, I paint a quartet of little Renault FT tanks in 1/35 scale (the 3D model is provided exclusively with the course). Each model showcases a different style of camouflage (those were done without stencils, though, either spraying freehand or using masking putty). However, on real-world Renault tanks, there were often these little card symbol markings (as a quick unit recognition tool I guess). With them, the tanks are about as cute as a machine of war could be. 😁

The stencils were drawn as a sketch in Fusion, using a simple Line tool, some mirroring, etc. Only the club symbol was a bit fiddly.

The masks are “two-stage”: first, I used a frame mask to paint the white square/circle/rhomboid…

…and then inserted the inner mask to paint the card symbol itself.

Now, let’s be honest, with this use case, we got close to the limit of the printed stencils: the symbols are small, so I recommend using a 0.25mm nozzle, with elephant foot compensation turned off in the slicer, to prevent slight distortion of the shapes.
Also, you have to be careful, as if the stencil lifts just a tiny bit from the surface, you’ll end up with slightly diffused outlines, which have to be retouched (or ignored 😎) later.

Paint chipping effects

The next trick is about airbrushing a simple paint chipping effect onto your model.

I used a picture of an actual wall with chipping and peeling paint coat, inserted into Fusion via the Insert Canvas tool, and then I sketched along the chipped patches using mostly just the regular Line tool.

Just for the sake of example, I sprayed some rusty brown on a bare silver PLA print. Note how I hold the stencil with tweezers to prevent fluttering; this ensures sharp outlines, otherwise, they end up slightly diffused (which is not necessarily an issue, though).

Also, for a realistic effect, make sure you turn the stencil a lot and don’t use the same shapes next to each other, as the human eye is very good at recognizing visual patterns. 😉

If you lift the stencil a bit higher above the surface, you can create diffused blotches instead.

These could be used for creating a mottle camouflage, or spotted animal hide, some weathering or preshading effect, like with the random blotchy stencil shown further above.

Faux raised details (rivet lines)

Another example shows how to use an airbrushed shading effect to imitate little raised details – here, a line of simple ballhead rivets.

Alright, this stencil is as primitive as they can get (sketched circle -> Linear Pattern in Fusion 😉). Attach it along the edge of the model and mask the surrounding surface.

Now, the trick is to load some diluted white into your airbrush and spray a perpendicular line going along the upper side of each hole. Make sure you aim rather slightly *above* the hole, not into it.

Then, use diluted black and spray another perpendicular line, this time along the lower side of each circle. Be careful and use quick strokes, as the thinned paint quickly becomes runny, as you can see on the second rivet. 😅

Voilá, the resulting effect. I actually failed to impress my colleague with it; he went like “so what?”, because from a distance, he thought I was showing him actual raised details, which is the whole point of the trick. 😁
As you can see, it takes a bit of practice to make the shading more or less even on each rivet; also, the effect would look better with more similar color tones (e.g., light blue and dark blue on intermediate blue).

Semi-realistic flames

The last example shows how to use stencils to paint semi-realistic flames, such as those painted on hot rod cars.

I use the stencils to paint the wavy flame shapes with white, then color them with yellow, orange, and red tones.

The keys to a realistic effect are, in my opinion, three. First, you need quite random-looking shapes (instead of the usual stylized pointy-cone flames), second, the right combination of sharp and diffused outlines (to imitate the “fresh” versus “dying” flame tongues), third, you need very bright colors and a lot of contrast (hence the white underpainting for the yellow, red, and orange).

In the course, there is a whole chapter just on the flame painting effects, using this Skoda model as a placeholder…

…but a real-deal vintage muscle car model is already in the pipeline. 💪 The plan is to upgrade the chapter to a fourth full-fledged sample project then.

Anyway, that’s all for now – but I plan to write at least one more blog article, teasing yet another chapter. 😉 In the meantime, I’d love to hear any feedback you might have on the airbrushing course – and also, feel free to share pictures of your sample project results. 🧡

Happy painting! 🎨