Desiccants, Tested Side By Side

July 19, 2024 by Jenny List 40 Comments

We’re so used to seeing a little sachet of desiccant drop out of a package when we open it, that we seldom consider these essential substances. But anyone who spends a while around 3D printing soon finds the need for drying their filament, and knowing a bit about the subject becomes of interest. It’s refreshing then to see [Big Clive] do a side-by-side test of a range of commonly available desiccants. Of silica gel, bentonite, easy-cook rice, zeolite, or felight, which is the best? He subjects them to exactly the same conditions over a couple of months, and weighs them to measure their efficiency in absorbing water.

The results are hardly surprising, in that silica gel wins by a country mile. Perhaps the interesting part comes in exploding the rice myth; while the rice does have some desiccant properties, it’s in fact not the best of the bunch despite being the folk remedy for an immersed mobile phone.

Meanwhile, this isn’t the first time we’ve looked at desiccants, in the past we’ve featured activated alumina.

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Low-Cost Cryocooler Pumps Out Cheap DIY Liquid Nitrogen

July 15, 2024 by Dan Maloney 18 Comments

A word of caution if you’re planning to try this cryocooler method for making liquid nitrogen: not only does it involve toxic and flammable gasses and pressures high enough to turn the works into a bomb, but you’re likely to deplete your rent account with money you’ll shell out for all the copper tubing and fittings. You’ve been warned.

In theory, making liquid nitrogen should be as easy as getting something cold enough that nitrogen in the air condenses. The “cold enough” part is the trick, and it’s where [Hyperspace Pirate]’s cryocooler expertise comes into play. His setup uses recycled compressors from cast-off air conditioners and relies on a mixed-gas Joule-Thomson cycle. He plays with several mixtures of propane, ethylene, methane, argon, and nitrogen, with the best results coming from argon and propane in a 70:30 percent ratio. A regenerative counterflow heat exchanger, where the cooled expanding gas flows over the incoming compressed gas to cool it, does most of the heavy lifting here, and is bolstered by a separate compressor that pre-cools the gas mixture to about -30°C before it enters the regenerative system.

There’s also a third compressor system that pre-cools the nitrogen process gas, which is currently supplied by a tank but will eventually be pulled right from thin air by a pressure swing adsorption system — basically an oxygen concentrator where you keep the nitrogen instead of the oxygen. There are a ton of complications in the finished system, including doodads like oil separators and needle valves to control the flow of liquid nitrogen, plus an Arduino to monitor and control the cycle. It works well enough to produce fun amounts of LN₂ on the cheap — about a quarter of the cost of commercially made stuff — with the promise of efficiency gains to come.

It does need to be said that there’s ample room for peril here, especially containing high pressures within copper plumbing. Confidence in one’s brazing skills is a must here, as is proper hydro testing of components. That said, [Hyperspace Pirate] has done some interesting work here, not least of which is keeping expenses for the cryocooler to a minimum.

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The Thermite Process Iron Foundry

July 5, 2024 by Jenny List 14 Comments

The thermite process is a handy way to generate molten iron in the field. It’s the reaction between aluminium metal and iron oxide, which results in aluminium oxide and metallic iron. It’s hot enough that the iron is produced as a liquid, which means it’s most notably used for in-field welding of things such as railway tracks. All this is grist to [Cody’s Lab]’s mill of course, so in the video below the break he attempts to use a thermite reaction in a rough-and-ready foundry, to make a cast-iron frying pan.

Most of the video deals with the construction of the reaction vessel and the mold, for which he makes his own sodium silicate and cures it with carbon dioxide. The thermite mix itself comes from aluminium foil and black iron oxide sand, plus some crushed up drinks cans for good measure.

The result is pretty successful at making a respectable quantity of iron, and his pour goes well enough to make a recognizable frying pan. It has a few bubbles and a slight leak, but it’s good enough to cook an egg. We’re sure his next try will be better. Meanwhile this may produce a purer result, but it’s by no means the only way to produce molten iron on a small scale.

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Watch SLS 3D Printed Parts Become Printed Circuits

June 20, 2024 by Donald Papp 38 Comments

[Ben Krasnow] of the Applied Science channel recently released a video demonstrating his process for getting copper-plated traces reliably embedded into sintered nylon powder (SLS) 3D printed parts, and shows off a variety of small test boards with traces for functional circuits embedded directly into them.

Here’s how it works: The SLS 3D printer uses a laser to fuse powdered nylon together layer by layer to make a plastic part. But to the nylon powder, [Ben] has added a small amount of a specific catalyst (copper chromite), so that prints contains this catalyst. Copper chromite is pretty much inert until it gets hit by a laser, but not the same kind of laser that sinters the nylon powder. That means after the object is 3D printed, the object is mostly nylon with a small amount of (inert) copper chromite mixed in. That sets the stage for what comes next.

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Can You Freeze-Dry Strawberries Without A Machine?

June 20, 2024 by Kristina Panos 46 Comments

Summer has settled upon the northern hemisphere, which means that it’s time for sweet, sweet strawberries to be cheap and plentiful. But would you believe they taste even better in freeze-dried format? I wouldn’t have ever known until I happened to get on a health kick and was looking for new things to eat. I’m not sure I could have picked a more expensive snack, but that’s why we’re here — I wanted to start freeze-drying my own strawberries.

While I could have just dropped a couple grand and bought some kind of freeze-drying contraption, I just don’t have that kind of money. And besides, no good Hackaday article would have come out of that. So I started looking for alternative ways of getting the job done.

Dry Ice Is Nice

Dry ice, sublimating away in a metal measuring cup. — Image via Air Products

Early on in my web crawling on the topic, I came across this Valley Food Storage blog entry that seems to have just about all the information I could possibly want about the various methods of freeze-drying food. The one that caught my eye was the dry ice method, mostly because it’s only supposed to take 24 hours.

Here’s what you do, in a nutshell: wash, hull, and slice the strawberries, then put them in a resealable bag. Leave the bag open so the moisture can evaporate. Put these bags in the bottom of a large Styrofoam cooler, and lay the dry ice on top. Loosely affix the lid and wait 24 hours for the magic to happen.

I still had some questions. Does all the moisture simply evaporate? Or will there be a puddle at the bottom of the cooler that could threaten my tangy, crispy strawberries? One important question: should I break up the dry ice? My local grocer sells it in five-pound blocks, according to their site. The freeze-drying blog suggests doing a pound-for-pound match-up of fruit and dry ice, so I guess I’m freeze-drying five entire pounds of strawberries. Hopefully, this works out and I have tasty treats for a couple of weeks or months. Continue reading “Can You Freeze-Dry Strawberries Without A Machine?” →

Autochrome For The 2020s

May 12, 2024 by Jenny List 2 Comments

For all intents and purposes, photography here in 2024 is digital. Of course chemical photography still exists, and there are a bunch of us who love it for what it is, but even as we hang up our latest strip of negatives to dry we have to admit that it’s no longer mainstream. Among those enthusiasts who work with conventional black-and-white or dye-coupler colour film are a special breed whose chemistry takes them into more obscure pathways.

Wet-collodion plates for example, or in the case of [Jon Hilty], the Lumière autochrome process. This is a colour photography process from the early years of the twentieth century, employing a layer of red, green, and blue grains above a photosensitive emulsion. Its preparation is notoriously difficult, and he’s lightened the load somewhat with the clever use of CNC machinery to automate some of it.

His web site has the full details of how he prepares and exposes the plates, so perhaps it’s best here to recap how it works. Red, green, and blue dyed potato starch grains are laid uniformly on a glass plate, then dried and pressed to form a random array of tiny RGB filters. The photographic emulsion is laid on top of that, and once it is ready the exposure is made from the glass side do the light passes through the filters.

If the emulsion is then developed using a reversal process as for example a slide would be, the result is a black and white image bearing colour information in that random array, which when viewed has red, green, and blue light from those starch filters passing through it. To the viewer’s eye, this then appears as a colour image.

We can’t help being fascinated by the autochrome process, and while we know we’ll never do it ourselves it’s great to see someone else working with it and producing 21st century plates that look a hundred years old.

While this may be the first time we’ve featured such a deep dive into autochrome, it’s certainly not the first time we’ve looked at alternative photographic chemistries.

Kaffa Roastery founder Svante Hampf shows a bag of their AI-conic coffee blend.

AI-Created Coffee Blend Isn’t Terrible

May 10, 2024 by Kristina Panos 12 Comments

Weren’t we just talking about coffee-based sacrilege the other day? Here’s something to make the single-origin bean snobs chew their espresso cups: an artisan roastery in Helsinki is offering a coffee blend created by artificial intelligence called AI-conic. The idea, of course, is that technology will lighten the workload needed to produce coffee.

This is an interesting development because Finland consumes the most coffee in the world, according to the International Coffee Organization. Coffee roasting is a highly-valued traditional artisan profession there, so it stands to reason that they might turn to technology for help.

Just like with scotch whisky, there’s nothing wrong with coffee blends outright. Bean blends are good for consistency, when you want every cup to taste pretty much exactly the same. Single-origin beans, though, are traceable to one location, and as a result, they usually have a distinct flavor based on the climate they’re grown in.

If you’re new to coffee, blends are a nice, safe way to start out. And, interestingly, the AI chose to make the blend out of four different types of beans instead of the usual two or three, despite being tasked with creating a blend that would suit the palates of coffee enthusiasts. But the coffee experts agreed that the AI blend was “perfect” and needed no human intervention. We probably won’t be getting to Finland anytime soon, so if you try it, let us know how it tastes!

Do you like cold brew? How would you like to be able to brew some in just three minutes?