DIY Spray Paint Mixer for Custom Colors

We’re all acquainted with mixing pink, yellow, and blue paint in varied ratios to immediately make all types of colours. This works nice for oils or watercolors, however fails in relation to cans of spray paint. The paint droplets can’t be blended as soon as they’re aerosolized. Consequently, though spray cans are nice for making use of even coats of paint to massive areas in a short time, spray-paint artists want a separate can for each shade they need to use—till now.

Again in 2018, once I first noticed skilled spray artists lugging dozens to tons of of cans to their work websites, I used to be impressed to begin noodling on an answer. I’ve labored at Google X, Alphabet’s “moonshot factory,” as a {hardware} engineer, and I’m now constructing a startup in mechanical-design software program. I’m no painter, however I do know my approach round mechatronics.

I wished my answer to be cheap and easy sufficient to construct as a DIY venture and practical sufficient for an artist to make use of, with out breaking their circulation. So I started prototyping a system that mixes base colours whereas they’re nonetheless in pressurized type from off-the-shelf cans.

This new rotary pinch valve might be opened and closed in tens of milliseconds and prevents backpressure from clogging traces.James Provost

I attempted just a few approaches the place pres-surized paint from the base-color cansfed by way of tubes right into a mixing channel, earlier than rising from a sprig head. To regulate the ratios, I made a decision to borrow a trick that may be acquainted to anybody who’s ever needed to management the bright-ness of an LED utilizing a microcontroller: pulse-width modulation. Initially, I used electronically managed solenoid valves to launch the paint from the cans. The paint would circulation right into a mixing channel for a relative period that corresponded to the ratio of the bottom colours required to make a given hue. Nonetheless, this failed as a result of completely different cans by no means have the identical inner stress. Every time two valves have been open on the identical time, the stress distinction would make paint circulation backward into the lower-pressure can.

In its place, I eliminated the blending channel and tried making the paint pulses from every can sequentially converge right into a tube in order that no multiple valve would ever be open at a time. Surprisingly, this labored completely. The backflow was eradicated, and it turned out that the pure turbulence of the circulation was adequate to combine the paints. Let’s say you need to produce a clementine orange shade. This requires yellow and pink paint in a ratio of 1:2, so the yellow valve opens for a time period, after which the pink valve opens for twice as lengthy. The system then retains repeating this cycle of pulses in a speedy tempo to immediately create the spray-paint shade you need.

The idea is simple, however making this work in follow took fairly a little bit of experimentation. First, I needed to decide the precise durations of pulses that may produce evenly blended colours, not simply their ratios. I additionally wanted to work out the scale of the tubing (too slender and also you’d get low spray power; too large and also you’d have paint accumulating within the tubes). Finally I settled on a most pulse period of 250 milliseconds and a tube diameter of 1 millimeter.

Inventing A New Valve

Though the system labored, the solenoid valves I used always clogged up. Designed for water purifiers, the valves didn’t stop paint from coming into the mechanism, the place the paint would harden. Furthermore, when the valves have been turned off, they may cease backflow provided that the inlet remained pressurized. So disconnecting a paint can from the system would trigger prompt leaking. Different off-the-shelf valves I attempted couldn’t cycle quick sufficient and have been too costly.

I had some spectacular failures alongside the best way of the type that solely pressurized paint can present.

So I created my very own mechanism: a high-speed, electronically managed, rotary pinch valve. It has a stepper motor that rotates a lever with a rolling bearing to constrict fluid circulation inside a versatile tube. This idea isn’t new—there’s one thing like them in each peristaltic pump. However I added a spring to firmly maintain the lever within the closed place in opposition to any again stress when the motor isn’t powered, making it a usually closed valve that isolates the hooked up can. Moreover, the valve is quick sufficient to be open for as little as 30 milliseconds.

I went by way of 4 main prototypes of the system earlier than reaching a working model, and I had some spectacular failures alongside the best way of the type that solely pressurized paint can present. The ultimate model makes use of 4 base colours—pink, yellow, blue, and white—with the colour combine managed by 4 knobs hooked up to an Arduino Nano and a small show. The circulation of paint is triggered by a push button positioned above the spray head, much like a sprig can’s nozzle.

Cans holding base colours (A) are hooked up to valves (B). An Arduino-based management panel (C) opens and closes valves to combine paint earlier than it’s aerosolized (E). By shortly opening and shutting valves with various durations in sequence (D), you possibly can combine paint in particular ratios to create desired colours.James Provost

The size of time a base shade’s paint valve might be open is one in all eight values between 30 and 250 ms. Which means that all the system—which I coincidentally dubbed Spectrum—can create tons of of distinct spray-paint colours immediately. It produces lower than 8⁴ (or 4,096) colours as a result of period ratios which might be a a number of of one another will produce the identical shade—for instance, 2:3 and 4:6. I added a power sensor to the push button, which permits for a gradient: Two shade mixes might be dialed in, and as I enhance my thumb’s stress on the button, the paint combine shifts from one shade to the opposite.

Spectrum’s varied fixtures are 3D-printed, and venture recordsdata and movies can be found by way of my web site at https://www.sandeshmanik.com/projects/spectrum. Preprints of technical descriptions of the rotary pinch valve and mixing methodology can be found on TechRxiv. The whole value for the invoice of supplies is lower than US $150.

Engaged on and off on the facet for about seven years, I lastly completed creating my system and writing the documentation in late 2025. After I posted a video to social media, I used to be heartened by the rapid optimistic response from spray-paint artists all over the world. I’m now creating step-by-step directions in order that nontechnical folks can construct their very own Spectrum paint sprayer. I sit up for seeing what creations artists out within the wild make!