An automatic color mixer, dispensing a mixture of red and yellow

The M5Stack Color Maker Can Mix Paint To Match Your Subject

October 11, 2021 by Robin Kearey 28 Comments

We’ve all learned in primary school art classes that blue and yellow make green, and that adding a little black to a color will make it darker. But what if you want to paint with a color that exactly matches something else? Usually, that requires a lot of trial and error (and paint), and the end result may not look the way you wanted after all.

To help aspiring artists, [Airpocket] made the M5Stack Color Maker. This is a device that reads out a color sensor and automatically mixes watercolor paint in the right proportions to match what it sensed. It dispenses drops of cyan, magenta, yellow and black paint (CMYK) into a small bowl, from which you can then apply it with a paintbrush.

The color sensor is similar in use to the color picker (or “dropper”) tool present in most graphics programs: simply point it at something that has the right color, and it will generate the correct values for you. It is based on an AMS TCS34725 color sensor, which is housed in a 3D-printed shell that also includes a white LED. The sensor outputs Red, Green and Blue (RGB) values, which are converted into the corresponding CMYK values by a Raspberry Pi Pico. A touch-sensitive screen allows the user to make adjustments before activating the paint pumps.

Those pumps are tube pumps, which have been specifically designed (and also 3D printed) to allow them to move tiny amounts of liquid while minimizing the pulsing motion typical with this type of pump. They are driven by stepper motors which are controlled by the Pi Pico.

Although many artists might prefer to mix their colors manually, the M5Stack makes mixing that exact shade of blue just that little bit easier. We can also imagine it might help those who are color blind and unable to clearly tell different colors apart. We’ve seen simple paint mixers for larger quantities of paint, and even robots that can do the actual painting for you. If you need a refresher on color theory, we’ve got you covered too.
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Automate Your Graffiti With The Graffomat!

September 30, 2021 by Jim Heaney 30 Comments

In Banksy’s book, Wall and Piece, there is a very interesting quote; “Imagine a city where graffiti wasn’t illegal, a city where everybody could draw whatever they liked…”. This sounds like it would be a very exciting city to live in, except for those of us who do not have an artistic bone in their body. Luckily, [Niklas Roy] has come up with the solution to this problem; the Graffomat, a spray can plotter.

The Graffomat is, in its creator’s own words, a “quick and dirty graffiti plotter.” It is constructed primarily from wood and driven by recycled cordless drills that pulls string pulleys to move the gantry. The Arduino Nano at the heart of the Graffomat can be controlled by sending coordinates over serial. This allows for the connection of an SD card reader to drip-feed the machine, or a computer to enable real-time local or over-the-internet control.

We are especially impressed with how [Niklas] handled positional tracking. The cordless drills were certainly not repeatable like a stepper motor, as to allow for open-loop control. Therefore, the position of the gantry and head needed to be actively tracked. To achieve this, the axes are covered with black and white striped encoder strips, that is then read by a pair of phototransistors as the machine moves along. These can then be paired with the homing switches in the top left corner to determine absolute position.

Graffomat is not the first automated graffiti machine we’ve covered. Read here about the robot that painted murals by climbing smokestacks in Estonia.

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Resin print before and after paint injection.

Resin 3D Prints Get A New Look With Paint Injection

August 27, 2021 by Dan Maloney 20 Comments

As cool as resin-based 3D printers are, they’re not without their shortcomings. One sore point, especially for those looking to document their prints, is that the translucent resins often favored for stereolithography can make the finest details difficult to see. Injecting paint into the model is how [Andrew Sink] decided to attack this problem, and the results are pretty striking.

For sure, this isn’t a problem that everyone making resin prints is going to face. Some resins are nicely opaque, and the fine details of a print show up just fine. But transparent resins lend a nice look to some projects, and might benefit from [Andrew]’s technique. It’s pretty much as simple as it sounds: choose a hollow model — or modify an existing one — print it up in the usual way, and clean thoroughly inside and out with isopropanol before curing under UV. Using a curing station that can get UV light up into the voids is probably a smart idea.

To finish off, the cured model is injected with acrylic paint. Nothing special here, just craft store acrylic in a syringe. [Andrew] seemed to prefer a thicker paint; we don’t want to second guess, but intuitively a thinner paint would seem to have some advantages. In any case, be sure to provide adequate vent holes for the displaced air. The video below has a few before and after shots, and the technique really works well to show off surface detail. Plus it just plain looks cool.

This seems like a good technique to keep in mind, and might even work well for hollow FDM prints done with transparent filaments. Still on the fence about FDM vs. SLA? We can help with that.

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Simple Tip Helps With Powder Coating Perfection On Difficult Parts

July 24, 2021 by Dan Maloney 8 Comments

To say that that the commercially available garden path lights commonly available at dollar stores are cheap is a vast overstatement of their true worthlessness. These solar-powered lights are so cheaply built that there’s almost no point in buying them, a fact that led [Mark Presling] down a fabrication rabbit hole that ends with some great tips on powder coating parts with difficult geometries.

Powder coating might seem a bit overkill for something as mundane as garden lights, but [Mark] has a point — if you buy something and it fails after a few weeks in the sun, you might as well build it right yourself. And a proper finish is a big part of not only getting the right look, but to making these totally un-Tardis-like light fixtures last in the weather. The video series below covers the entire design and build process, which ended up having an aluminum grille with some deep grooves. Such features prove hard to reach with powder coating, where the tiny particles of the coating are attracted to the workpiece thanks to a high potential difference between them. After coating, the part is heated to melt the particles and form a tough, beautiful finish.

But for grooves and other high-aspect-ratio features, the particles tend to avoid collecting in the nooks and crannies, leading to an uneven finish. [Mark]’s solution was to turn to “hot flocking”, where the part is heated before applying uncharged coating to the deep features. This gets the corners and grooves well coated before the rest of the coating is applied in the standard way, leading to a much better finish.

We love [Presser]’s attention to detail on this build, as well as the excellent fabrication tips and tricks sprinkled throughout the series. You might want to check out some of his other builds, like this professional-looking spot welder.

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New Whitest Paint Might Help Fight Climate Change

April 16, 2021 by Lewin Day 69 Comments

It’s hot! Hotter than it used to be, and too hot for things to remain nice in the future. The sun keeps beating down, and as our greenhouse gas emissions continue to blanket the earth, more of that heat is trapped, leading to the steady uptick in global average temperatures. Reducing these emissions can help, but there’s other possibilities too. A team of researchers with a new very white paint think it might be of some use in solving the problem.

Thermal imaging shows the white paint’s ability to cool a surface below ambient temperature, by radiating away excess heat.

The new “whitest white” paint comes to us from Purdue University in the US. It’s capable of reflecting 98% of sunlight reaching its surface, a big step up over the typical 80-90% of conventional white paints. Additionally, it doesn’t absorb UV light, and can also radiate out heat in infrared wavelengths that pass out of the atmosphere. This allows the paint to cool surfaces below ambient temperature. The paint achieves these feats by using barium sulphate as a pigment, which doesn’t absorb UV like conventional titanium dioxide white pigments do. The paint also uses a lot of pigment – 60%, versus 20-40% in a more typical paint. This is similar to techniques used in producing Vantablack, the blackest black acrylic paints.

The hope is that by painting roofs and walls of buildings with white paint, more sunlight will be reflected back out into space, and buildings will be naturally cooler with less reliance on air conditioning, helping to reduce emissions. This could go a long way to solving the heat island effect in many major cities. Municipalities around the world have already begun adopting the technique, from California, to New York and Ahmedabad. It’s an easy thing to do, with few drawbacks, so we expect to see the practice grow more popular in coming years. While it won’t solve the climate crisis on its own, the world could surely use every bit of help it can get.

When Is Apple Beige Not Apple Beige?

February 7, 2021 by Jenny List 20 Comments

If we cast our minds back a few decades, almost all computers were a beige colour. “Beige box” even became a phrase for a generic PC, such was their ubiquity. Long before PCs though there were other beige computers, and probably one of the first to land on the desks of enthusiasts rather than professionals was the Apple ][. But exactly what beige colour was it? It’s a question that interested [Ben Zotto], and his quest led him through a fascinating exploration of a colour most of us consider to be boring.

We’re used to older beige computers becoming yellow with time, as the effect of light and age causes the fire retardants in their plastic to release bromine. But the earlier Apple products haven’t done this, because their beige came not from the plastic but from a paint. [Ben] was lucky enough to find a small pot of touch-up paint from Apple that was made available to dealers, so notwithstanding any slight pigment changes from its age, he set off in pursuit of its origin.

Along the way to identifying a modern Pantone shade (Pantone 14–0105 TPG, for the curious) he treats us to a cross-section of Apple’s early colour history with reference to the memories of early Apple luminaries. He even suggests readily available shades that could suffice, pointing to Gloss Almond Rust-Oleum spray paint.

So should you wish to colour-match to an early Apple, now you can. If you have a Commodore or an Atari though, maybe your task is a little easier.

Purdue’s Powerful Paint Could Cancel Climate Change

November 5, 2020 by Kristina Panos 76 Comments

What if a building could stay cool simply because of its paint job? We’re not talking about putting flames on the sides. Purdue engineers have come up with a formulation of white paint that reflects the heat from sunlight and keeps surfaces cooler than their surroundings. Depending on the location, a building with this paint on the roof may not need air conditioning.

Radiative cooling paint is not a completely new animal, but the formulation developed at Purdue is quite impressive compared to commercially-available paints that only reflect 80-90% of sunlight.

Purdue’s paint reflects 95.5% of sunlight. It can keep surfaces up to 18°F cooler than their surroundings, even in direct sunlight. Where does the heat go? The paint radiates infrared heat, so it escapes the atmosphere and goes into deep space.

How does it do this? With abundantly available calcium carbonate fillers — the chalky stuff that antacids are made of. The paint absorbs next to no UV rays because of the wide band gaps in the atomic structure of calcium carbonate. Take a brief tour of this amazing paint after the break.

We wonder how many rooftops and roadways we’d have to paint with this stuff to have a chance at reversing climate change. It’s not terribly expensive to make, so the problem shifts to widespread education and adoption. What do you think?

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