Color Mixing Spray Paint On The Fly

March 1, 2026 by Zoe Skyforest 40 Comments

One of the problems with being a graffiti artist is that you have to carry around a different spray can for each color you intend to use. [Sandesh Manik] decided to solve this problem by building a rig that can produce a wider range of colors by mixing the paint from several cans at once.

The project is called Spectrum. It uses four off-the-shelf spray paint cans—colored red, blue, yellow, and white—and mixes them to create a wider range of colors. All four cans are hooked up to a single output nozzle via a nest of tubing and a four-to-one tube manifold. Key to controlling the flow of paint is a custom device which [Sandesh] calls the “rotary pinch valve,” with one fitted to the feed line coming from each spray can. These valves use a motor-driven lever to pinch a plastic tube shut, allowing them to control the paint flow. This design keeps the mechanism and paint completely separate, which was important to stop paint from fouling the valves in short order. It also prevents backflow, which keeps the paint going towards the outlet and prevents ugly messes. By quickly actuating the valve, the paint flow from each can is modulated to mix various colors as desired.

The mixing valves are under the command of an Arduino Nano. The microcontroller reads a series of knobs to select the amount of each component color to mix, and displays relevant information on a screen. Then, when a push button is pressed, the valves are actuated to spit out the right amount of each paint from the atomizer nozzle. [Sandesh] went so far as to include an advanced “gradient” mode, where a force-sensitive button allows the device to transition smoothly from one color to another depending on how hard the button is pushed.

It’s a neat concept which we’d love to see explored further, perhaps with a more traditional selection of CMYK paints rather than the more unusual red, yellow, blue, and white. We’ve also seen some fun spray paint projects before, like this neat wall-mount plotter.

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One of four MDF half-tone blocks coming off the laser cutter.

Laser Cutter Plus CYMK Spraypaint Equals Full-Color Prints

December 16, 2025 by Tyler August 13 Comments

This is one of those fun hacks that come about from finding a product and going “I wonder if I could…” — in this case, artist/YouTuber [Wesley Treat] found out his favourite vendor makes spray cans in CYMK colours– that is the Cyan, Yellow, Magenta and blacK required for subtractive printing. Which got him wondering: can I make full-colour prints with this paint?

MDF block print — The MDF-based print, with naive half-tone dots.

His answer was “yes”, and the process to do so is fairly simple. First, split the image into colour channels, generate a half-tone pattern for each one, and carve it out of MDF on the laser. Then spray the MDF with the appropriate colour spray paint. Press the page against each block in turn, and voila! A full colour print block print, albeit at very low DPI compared to your average inkjet.

Now, you might be wondering, why half-tone instead of mixing? Well, it turns out that these CYMK paints are too opaque for that to work in a block-printing process. At least with a naive spray technique; [Weseley] does admit a very fine mist might be able to make that work. The second question is why not just hook the rattle cans into a CNC machine for a paint-based mega inkjet? That’s a great question and we hope someone tries it, but [Weseley] evidently likes block-printing so he tried that first.

The Mylar stencil print, with a more artistic half-tone pattern.

Laser-ablating enough MDF away to make decent print blocks took too long for [Weseley]’s tastes, however, so he switched to using mylar stencils. Instead of spraying a block and pressing onto it, the paint is sprayed through the stencil. The 10 mil Mylar not only cuts faster, but can support finer detail. Though the resulting prints lose some of the artistic flair the inconsistencies block printing brings, it probably looks better.

If you prefer to skip the manual paint-can-handling, perhaps we can interest you in a spray-can plotter. If you do like manually flinging paint, perhaps you could try this dot-painting spray can attachment, for a more self-directed half-tone.

Thanks to [Keith Olson] for the tip.

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Sandpaper Alternatives For 3D Prints

January 4, 2024 by Bryan Cockfield 19 Comments

A finished 3D print, especially plastic deposition types, often have imperfections in them from the process of laying down each layer of material and from the printer itself. For small batches or one-off parts, we might reach for a few pieces of sandpaper to smooth out these rough edges. While that might work for a small number of parts, it’s not always the best or lowest-effort option for refining these prints. There are a few alternative methods to try out if your fingers are getting sore, though.

Rather than removing material as sandpaper does, most of these methods involve adding material to the print in order to fill in the rough edges of the print. There is a 3D-print-specific product listed called 3D Gloop! which is generally used as a glue to hold plastic parts together, but can also act as a fill in a pinch. Two other similar methods, one using spray paint and polyurethane and the other using epoxy, are more general-purpose ways of finishing the prints with a more natural texture than the printer will produce on its own. They’re not all additive, though; the final (and perhaps, most toxic) method here to achieve a smooth surface on a print uses solvent to remove some of the material instead.

While sandpaper does have its time and place, certain prints may lend themselves more to being finished by one of these other methods especially if they are overly complex, fragile, or an unusual size. Take note of the safety gear you’ll want to have on hand for most of these methods, though, as gloves and a respirator are highly encouraged and possibly helpful even if using only sandpaper. These aren’t the only ways of finishing 3D prints, either. Some of our other favorites are using glazing putty or silver for the finish.

An Amiga 500 with a blue case and blue accessories

Restored Amiga 500 Is Blue – And Glows In The Dark

July 21, 2023 by Robin Kearey 5 Comments

Few things are as satisfying to watch as a good retrocomputer restoration project – we’re always happy to see someone bring a rusty old Commodore, Apple or Atari back to life. The goal is typically to get the machine as close to its original state as possible, except for perhaps a few non-intrusive mods like memory upgrades. [Drygol] however, had already done this so many times that he thought it was time to take a different route for once, and apply some creativity to an old Amiga 500 case. Originalists may shudder, but we quite like his funky blue-and-yellow A500 mod.

An Amiga 500 with a poor blue-and-yellow paint job — Missing keys, random stickers and an ugly paint job: the A500 wasn’t looking great at the beginning

To be fair, [Drygol] wasn’t the first one to modify this specific Amiga’s case: one of its previous owners had already applied a rather shoddy blue paint job and defaced it with some stickers. [Drygol] decided to stick with the basic idea, but do it right this time. First he removed the old paint using concentrated lye, then gave it a fresh coat of blue. He also applied glow-in-the-dark paint to the Amiga logo embossed in the case and added a fluorescent yellow laser-cut circuit board ornament. It took a bit of experimenting to get all these elements just right, but the end result definitely looks the part.

The insides of the Amiga also needed some TLC: [Drygol] competely cleaned and lubricated the floppy drive, gave the motherboard a good ultrasonic scrub, and replaced dodgy capacitors all over. He expanded the RAM from 512 kB to 1 MB and added a Gotek floppy emulator, which can work in parallel with the original disk drive. To make the Gotek easy to operate, [Drygol] placed its OLED screen and a pair of touch-sensitive buttons in a cutout on the front of the case.

A matching blue mouse and gamepad, both connected through the MouSTer adapter, complete the setup. The result is a good-looking A500 with some modern conveniences that’s perfect for exploring the Amiga’s extensive software library. If custom colors aren’t your thing, you’ll be happy to know that the original shade of grey or beige might be available for your retro console, too.

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Dot-Painting Graffiti Machine Is Wonderfully Simple

November 10, 2022 by Zoe Skyforest 28 Comments

Traditionally, when many of us think of graffiti, we think of artists spraying away with simple paint cans. However, there’s often a lot of tech and art that goes into the field these days. [Vitaly Tesh] built himself a impressive dot-painting spray rig that’s really rather nifty.

The dot maker performed ably in this piece by [Vitaly].

The build starts with [Vitaly] using a heated Stanley knife to cut away a propeller assembly from a small toy drone. He then fits a small plastic disc to the motor in place of the prop. The disc has a cutout so that as it spins, it only allows paint to pass at certain times. The whole package bolts onto a regular spray can, so it can be used with any paint color or brand that’s desired.

The spray can paints individual dots on the wall at varying distances apart, thanks to the spinning disc. Varying the speed of the motor or the rate at which the can is moved relative to the wall changes the pitch of the dots. Importantly, [Vitaly] included a drip capture system so that paint that doesn’t pass out of the dot aperture doesn’t leak all over his hands or the wall, ruining the piece.

We’ve seen robots put to work painting murals on walls, too. Video after the break.

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Retrocomputing Spray Paints: Amiga Beige, Commodore, And ATARI Grey

September 1, 2020 by Donald Papp 19 Comments

[retrohax] has provided vintage computer guidance for years, and part of that guidance is this: sometimes using paint as part of restoration is simply unavoidable. But the days of tediously color-matching to vintage hardware are gone, thanks to [retrohax] offering custom-mixed spray paints in Amiga 500 Beige, C-64 Beige, and ATARI ST/SE Grey. (At the moment only delivery within Poland is available due to shipping restrictions, but [retrohax] is working on a better solution.)

As a companion to making these vintage colors available, there is also a short how-to guide on how to properly prep and spray paint a computer case for best results that talks a little about the challenges in color matching to vintage hardware, and how getting custom paints mixed makes life much easier. Hackers may value making do with whatever is available, but we can also appreciate the value of having exactly the right material or tool for the job.

It’s not every day we see someone mixing custom spray paint colors, but off the shelf options don’t always cut it. Another example of getting specialty materials made from the ground up is custom plywood specifically designed for laser-cutting puzzles, something done because the troubles that came with off-the-shelf options were just not worth the hassle.

Beat The Streets With This Text Spraying Robot

October 25, 2019 by Sharon Lin 25 Comments

In the midst of striking for climate change awareness, you may need some extra hands. That’s what [Anred Zynch] thought when they built Strettexter, the text-spraying writing robot that sprays onto streets.

The machine is loaded with 8 spray cans placed into a wooden box (a stop line with a wooden ledge to prevent the cans from falling out) and is fixed on top of a skateboard. It uses a PWN/Servo shield soldered onto an Arduino Uno connected to 8 servo motors (TowerPro SG90s) to control each of the spray bottles. A table converts every character into 5×8 bit fonts to fit the size of the spraying module. The device also includes a safety switch, as well as an encoder for measuring the horizontal distance traveled.

The Strettexter is activated by pulling on the skateboard once it’s been set up and connected to power (for portability, it uses a 8000mAh power bank). In its current configuration, the words stretch out pretty long, but some additional testing will probably lead to better results depending on the constraints of your canvas. The shorter the words, the more difficult it is for the white text to be legible, since there is significant spacing between printed bits.

We don’t condone public vandalism, so use this hack at your own discretion.

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