A complex piece of laboratory glassware with liquid metal inside

A Liquid Metal Fountain That Works At Room Temperature

A fountain is a great way of adding a little flair to an otherwise boring pond. All you need is a pump, a filter and some pipes, along with a nozzle to scatter the pressurized water in some aesthetically pleasing way. Fountains are generally quite safe: if any of the parts malfunction, the worst thing that can happen is some minor flooding.

How different this is for [Advanced Tinkering]’s recent project, the NaK Fountain. If this one were to spring a leak, it’s quite likely to take out its surroundings in a huge fireball. That’s because the fluid inside is an alloy of sodium and potassium in about a 1:3 ratio, known as NaK (pronounced like “knack”), which is a liquid at room temperature. Unfortunately, it’s also highly reactive: NaK oxidizes quickly when exposed to air and can even catch fire spontaneously. Contact with water will result in a fiery explosion that scatters corrosive liquids everywhere. Continue reading “A Liquid Metal Fountain That Works At Room Temperature”

Make Your Own Vinegar

Making fermentation work for us is one of the original hacks that allowed humans to make food last longer, and festivities more interesting. [Mike G] has been experimenting with making his own vinegar, and found the end product to be a delicious addition to his cooking.

The first step is similar to making alcoholic beverages. Take something that contains sugar, like fruit, mix it with water and let stand. Wild yeast will feed on the sugar and create alcohol. Once the alcohol content reaches the 6-12% range, the resulting liquid can be separated from the solids and left exposed to the air. This allows Acetobacter bacteria to convert the alcohol into acetic acid, producing vinegar. The entire process takes around 30 days.

[Mike]’s first round of experiments was mainly with fresh fruit, with the addition of raisins. To prevent white mold from forming the mixtures should be stirred daily, but life got in the way and mold got out of control on all the fruits, except for the raisins. This gave [Mike] the to try another round with dried fruit, which was significantly less prone to mold, and produced deliciously flavored vinegar. [Mike] also demonstrated their use in a couple of mouth-watering dishes.

The DIY vinegar production process is just begging for some fermentation monitoring and automation tech. We’ve seen plenty of sourdough and beer production projects, which we suspect could also be applied to vinegar production with some minor changes.

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Keycap Shine? No, Shiny Keycaps

No matter how often you wash your hands, ABS keycaps will eventually exhibit shine wherever you strike them the most. And that’s the problem right there: the shine might be okay if it were somehow uniform across the surface of the keycaps, but instead it just tends to make one feel seen. And since there’s really nothing you can do except to replace your keycaps (or start with PBT), you might as well embrace the shine, right?

Well, that’s how [mmalluck] feels, anyway. He recently experimented with using acetone vapors to refinish a set of keycaps from Drop, making them super-duper shiny in the process. Now, the operative word here is vapors, because straight acetone would acid-wash those ‘caps faster than you can say ‘bad idea jeans’.

So to that end, [mmalluck] poured acetone in a glass cake pan, used a piece of cardboard to separate the keycaps from the acetone, and covered it all with a glass cutting board. It doesn’t take very long to achieve a good result, and [mmalluck] says it’s better to err on the side of too-short instead of risking reaching the point of too-melted.

We wouldn’t have thought we’d react this way, but we think they’re pretty cool looking. That particular set seems just right for this process, which makes them look like new old-stock typewriter keys or something. Looks way better than the ultra-personalized shine of usage. What do you think? Let us know in the comments.

Via KBD #90

Scavenging CDs For Flexible Parts

CDs are becoming largely obsolete now, thanks to the speed of the internet and the reliability and low costs of other storage media. To help keep all of this plastic out of the landfills, many have been attempting to find uses for these old discs. One of the more intriguing methods of reprurposing CDs was recently published in Nature, which details a process to harvest and produce flexible biosensors from them.

The process involves exposing the CD to acetone for 90 seconds to loosen the material, then transferring the reflective layer to a plastic tape. From there, various cutting tools can be used to create the correct pattern for the substrate of the biosensor. This has been shown to be a much more cost-effective method to produce this type of material when compared to modern production methods, and can also be performed with readily available parts and supplies as well.

The only downside to this method is that it was only tested out on CDs which used gold as the conducting layer. The much more common aluminum discs were not tested, but it could be possible with some additional research. So, if you have a bunch of CD-Rs laying around, you’re going to need to find something else to do with those instead.

Thanks to [shinwachi] for the tip!

Does Hot Water Freeze Faster Than Cold? Debate Continues Over The Mpemba Effect

Does hot water freeze faster than cold water? On its face this idea seems like it should be ridiculously simple to test, and even easier to intuit, but this question has in fact had physicists arguing for decades.

Erasto Mpemba’s observations initiated decades of research into the Mpemba effect: whether a liquid (typically water) which is initially hot can freeze faster than the same liquid which begins cold.

There’s a name for the phenomenon of something hot freezing faster than something cold: the Mpemba effect,  named for Erasto Mpemba (pictured above) who as a teenager in Tanzania witnessed something strange in high school in the 1960s. His class was making ice cream, and in a rush to secure the last available ice tray, Mpemba skipped waiting for his boiled milk-and-sugar mixture to cool to room temperature first, like everyone else had done. An hour and a half later, his mixture had frozen into ice cream whereas the other students’ samples remained a thick liquid slurry.

Puzzled by this result, Mpemba asked his physics teacher what was going on. He was told “You were confused. That cannot happen.” Mpemba wasn’t convinced by that answer, and his observations ultimately led to decades of research.

What makes this question so hard to nail down? Among many of the issues complicating exactly how to measure such a thing is that water frankly has some odd properties; it is less dense as a solid, and it is also possible for its solid and liquid phases to exist at the same temperature. Also, water in the process of freezing is not in equilibrium, and how exactly things act as they relax into equilibrium is a process for which — physics-wise — we lack a good theory. Practically speaking, it’s also a challenge how to even accurately and meaningfully measure the temperature of a system that is not in equilibrium.

But there is experimental evidence showing that the Mpemba effect can occur, at least in principle. How this can happen seems to come down to the idea that a hot system (having more energy) is able to occupy and explore more configurations, potentially triggering states that act as a kind of shortcut or bypass to a final equilibrium. In this way, something that starts further away from final equilibrium could overtake something starting from closer.

But does the Mpemba effect actually exist — for example, in water — in a meaningful way? Not everyone is convinced, but if nothing else, it has sure driven a lot of research into nonequilibrium systems.

Why not try your own hand at investigating the Mpemba effect? After all, working to prove someone wrong is a time-honored pastime of humanity, surpassed only in popularity by the tradition of dismissing others’ findings, observations, or results without lifting a finger of your own. Just remember to stick to the scientific method. After all, people have already put time and effort into seriously determining whether magnets clean clothes better than soap, so surely the Mpemba effect is worth some attention.

An Anodiser That Does Gradients

Anodizing aluminium, the process of electrolytic build up of the metal’s the oxide layer in the presence of dyes to create colored effects, is such a well-established process that we probably all have anodized items within sight. It’s usually an industrial mass-production process that creates a uniform result, but there’s an anodizing machine from a Dutch design studio which promises to place anodized aluminium in a new light. Studio Loop Loop’s Magic Color Machine enacts a small-scale automated anodizing process driven by a microcontroller, and is capable of effects such as gradated colors.

Unfortunately their website is long on marketing and short on technical details, but the basic function of a line of chemical baths with a pulley to lower and lift the item being anodized shouldn’t be too difficult for any Hackaday reader to understand. There’s a short video clip posted on Instagram which also gives some idea. It’s a powerful idea that should lead to some eye-catching work for their studio, but its interest here lies in the techniques it might inspire others to try. We look forward to an open-source version of a gradated anodize. Meanwhile if anodizing takes your fancy, it’s a subject we’ve visited before.

Mining And Refining: Helium

With a seemingly endless list of shortages of basic items trotted across newsfeeds on a daily basis, you’d be pardoned for not noticing any one shortage in particular. But in among the shortages of everything from eggs to fertilizers to sriracha sauce has been a growing realization that we may actually be running out of something so fundamental that it could have repercussions that will be felt across all aspects of our technological society: helium.

The degree to which helium is central to almost every aspect of daily life is hard to overstate. Helium’s unique properties, like the fact that it remains liquid at just a few degrees above absolute zero, contribute to its use in countless industrial processes. From leak detection and welding to silicon wafer production and cooling the superconducting magnets that make magnetic resonance imaging possible, helium has become entrenched in technology in a way that belies its relative scarcity.

But where does helium come from? As we’ll see, the second lightest element on the periodic table is not easy to come by, and considerable effort goes into extracting and purifying it enough for industrial use. While great strides are being made toward improved methods of extraction and the discovery of new deposits, for all practical purposes helium is a non-renewable resource for which there are no substitutes. So it pays to know a thing or two about how we get our hands on it.

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