So far in this series, we’ve talked about man-made byproducts — Fordite, which is built-up layers of cured car enamel, and Trinitite, which was created during the first nuclear bomb test.

But not all byproducts are man-made, and not all of them are basically untouchable. Some are created by Mother Nature, but are nonetheless dangerous. I’m talking about fulgurites, which can form whenever lightning discharges into the Earth.

It’s likely that even if you’ve seen a fulgurite, you likely had no idea what it was. So what are they, exactly? Basically, they are natural tubes of glass that are formed by a fusion of silica sand or rock during a lightning strike.

Much like Lichtenberg figures appear across wood, the resulting shape mimics the path of the lightning bolt as it discharged into the ground. And yes, people make jewelry out of fulgurites.

Lightning Striking Again

Lightning is among the oldest observed phenomena on Earth. You probably know that lightning is just a giant spark of electricity in the atmosphere. It can occur between clouds, the air, or the ground and often hits tall things like skyscrapers and mountaintops.

Lightning is often visible during volcanic eruptions, intense forest fires, heavy snowstorms, surface nuclear detonations, and of course, thunderstorms.

In lightning’s infancy, air acts as an insulator between charges — the positive and negative charges between the cloud and the ground. Once the charges have sufficiently built up, the air’s insulating qualities break down and the electricity is rapidly discharged in the form of lightning.

When lightning strikes, the energy in the channel briefly heats up the air to about 50,000 °F, which is several times the surface of the Sun. This makes the air explode outward. As the shock wave’s pressure decreases, we hear thunder.

Of Sand and Rock and Other Stuff

Fulgurites, also known as fossilized lightning, don’t have a fixed composition: they are composed of whatever they’re composed of at the time of the lightning strike. Four main types of fulgurites are officially recognized: sand, soil, caliche (calcium-rich), and  rock fulgurites. Sand fulgurites can usually be found on beaches or in deserts where clean sand devoid of silt and clay dominates. And like those Lichtenberg figures, sand fulgurites tend to look like branches of tubes. They have rough surfaces comprised of partially-melted grains of sand.

When sand fulgurites are formed, the sand rapidly cools and solidifies. Because of this, they tend to take on a glassy interior. As you might imagine, the size and shape of a fulgurite depends on several factors, including the strength of the strike and the depth of the sand being struck. On average, they are 2.5 to 5 cm in diameter, but have been found to exceed 20 cm.

Soil fulgurites can form in a wide variety of sediment compositions including clay-, silt-, and gravel-rich soils as well as leosses, which are wind-blown formations of accumulated dust. These also appear as tubaceous or branching formations, vesicular, irregular, or a combination thereof.

Calcium-rich sediment fulgurites have thick walls and variable shapes, although it’s common for multiple narrow channels to appear. These can run the gamut of morphological and structural variation for objects that can be classified as fulgurites.

Rock fulgurites are typically found on mountain peaks, which act as natural lightning rods. They appear as coatings or crusts of glass formed on rocks, either found as branching channels on the surface, or as lining in pre-existing fractures in the rock. They are most often found at the summit or within several feet of it.

Fact-Finding Fulgurites

Aside from jewelry and such, fulgurites’ appeal comes in wherever they’re found, as their presence can be used to estimate the number of lightning strikes in an area over time.

Then again there’s some stuff you may not necessarily want to use in jewelry making. Stuff that can be found in the dark, dank corners of the Earth. Stay tuned!

While some byproducts recall an idyllic piece of Americana, others remind us that the past is not always so bright and cheerful. Trinitite, created unintentionally during the development of the first atomic bomb, is arguably one of these byproducts.

Whereas Fordite kept growing back for decades, all Trinitite comes from a single event — the Trinity nuclear bomb test near Alamogordo, New Mexico on July 16, 1945. Also called ‘atomsite’ and ‘Alamogordo glass’, ‘Trinitite’ is the name that stuck.

There wasn’t much interest in the man-made mineral initially, but people began to take notice (and souvenirs) after the war ended. And yes, they made jewelry out of it.

Although there is still Trinitite at the site today, most of it was bulldozed over by the US Atomic Energy Commission in 1953, who weren’t too keen on the public sniffing around.

There was also a law passed that made it illegal to collect samples from the area, although it is still legal to trade Trinitite that was already on the market. As you might expect, Trinitite is rare, but it’s still out there today, and can even be bought from reputable sources such as United Nuclear.

The Formation Event

On that fateful day, the plutonium bomb nicknamed “Gadget” was strapped to a 100-foot tower atop a bed of sandy soil. The detonation left a crater half a mile across and eight feet deep of radioactive glass.

While at first it was assumed that the sand that became Trinitite melted at ground level, it has somewhat recently been theorized that the sand was sucked up into the fireball, liquefied, then rained down to form a sheet of glass of varying thickness, composition, and topology.

It’s estimated that the glass was formed by 4,300 gigajoules of heat energy, and the sand was exposed to a minimum temperature of 1,470 °C (2,680 °F) and super-heated for two or three seconds before solidifying into Trinitite.

In September 1945, Time magazine reported that the site looked like “a lake of green jade”, with the glass taking strange shapes, like those of “lopsided marbles… broken, thin-walled bubbles, green, worm-like forms.” The marbles suggest that some material solidified in the air on the way down.

Not all Trinitite is bottle-green, although most of it is. Some red Trinitite was discovered in one part of the site, and there are rare black pieces that are thought to contain iron. It’s been theorized that green Trinitite gets its color from the material in the support tower, while red specimens include copper from the electrical wiring.

A Unique Composition

Geologically speaking, Trinitite is made up of a chaotic mixture that varies both its structure and composition. A typical sample has been described as 1 to 3 cm thick, with a smooth side and a rough side from landing in a molten state on the desert floor. The upper surface is usually sprinkled with dust, while the bottom is thicker and grades into the soil it came from. Far from completely solid, it is estimated that around 30% of Trinitite is void space, and usually has cracks.

Optically, there are two forms of Trinitite with different refraction indices — the lower-index type is mostly silicon dioxide, while the higher-index glass has mixed components. Although deemed safe to handle, Trinitite is measurably radioactive. The level of radioactivity fluctuates based on the size of the specimen and its distance from ground zero.

The First of Many Atomsites, Unfortunately

As you might imagine, glassy residues remain wherever nuclear weapons detonate at or near ground level. Some scientists prefer to call all other glasses ‘atomsite’, although plenty of site- and creator-specific names have been given to the byproducts of other detonations. It was discovered in 2016 that, following the bombing of Hiroshima, between 0.6% and 2.5% of the sand on local beaches consisted of fused glass spheres that had formed. It has been called Hiroshimaite.

Trinitite is known as a melt glass or glass melt, which basically means that the silica from the ground bonded with surrounding minerals originating from both the tower and the bomb itself. While this formation process is a man-made one, there are similar natural processes that produce glassy byproducts. Stay tuned!

Sand has been used to keep track of the passage of time since antiquity. But using sand to make a persistence of vision digital clock (English translation) is something altogether new. And it’s pretty cool, too.

The idea behind the timepiece that [Álvaro Gómez Giménez] built is pretty simple drop a tiny slug of fine sand from a hopper and light it up at just the right point in its fall. Do that rapidly enough and you can build up an image of the digits you want to display. Simple in concept, but the devil is in the details. Sand isn’t the easiest material to control, so most of the work went into designing hoppers with solenoid-controlled gates to dispense well-formed slugs of sand at just the right moment. Each digit of the clock has four of these gates in parallel, and controlling when the 16 gates open and close and when the LEDs are turned on is the work of a PIC18F4550 microcontroller.

The build has a lot of intricate parts, some 3D printed and some machined, but all very carefully crafted. We particularly like the big block of clear plastic that was milled into a mount for the main PCB; the translucent finish on the milled surfaces makes a fantastic diffuser for the 96 white LEDs. The clock actually works a lot better than we expected, with the digits easy to make out against a dark background. Check it out in the video below.

Between the noise of 16 solenoids and the sand getting everywhere, we’d imagine it wouldn’t be a lot of fun to have on a desk or nightstand, but the execution is top-notch, and an interesting and unusual concept we haven’t seen before. Sure, we’ve seen sandwriting, but that’s totally different.

Thanks to [ThoriumBR] for the tip.

Research activity into 3D printing never seems to end, with an almost constant stream of new techniques and improvements upon old ones hitting the news practically daily. This time, the focus is on a technique we’ve not covered so much, namely binder jetting additive manufacturing (BJAM for short, catchy huh?) Specifically the team from Oak Ridge National Laboratory, who have been exploring the use of so-called hyperbranched Polyethyleneimine (PEI) as a binder for jetting onto plain old foundry silica sand (nature, free access.)

The PEI binder was mixed with a 75:25 mix of water and 1-propanol (not to be mixed up with 2-propanol aka isopropanol) to get the correct viscosity for jetting with a piezoelectric print head and the correct surface tension to allow adequate powder bed penetration, giving optimal binding efficiency. The team reported a two-fold increase in strength over previous jetting techniques, however, the real news is what they did next; by infusing the printed part (known as the green part) with common old ethyl cyanoacrylate (ECA, or super glue to us) the structural strength of the print increased a further eight times due to the reaction between the binder and the ECA infiltrate.

To further bestow the virtues of the PEI binder/ECA mix, it turns out to be water-soluble, at least for a couple of days, so can be used to make complex form washout tooling — internal supports that can be washed away. After a few days, the curing process is complete, resulting in a structure that is reportedly stronger than concrete.  Reinforce this with carbon fiber, and boy do you have a tough building material!

Not bad for some pretty common materials and a simple printing process.

We covered a similar binder jetting process for using sawdust a little while ago, and a neat way of printing with metal powder by carrying it in a stream of argon and cooking it with a laser, but there is an opening for a DIY effort to get in on the binder jetting game.

Thanks [Victor] for the tip!

Many of us have marveled at art installations that feature marbles quietly and ceaselessly tracing out beautiful patterns in sand. [DIY Machines] is here to show us that it’s entirely possible to build one yourself at home!

The basic mechanism is simple enough. The table uses a Cartesian motion platform to move a magnet underneath a table. On top of the table, a metal sphere attached to the magnet moves through craft sand to draw attractive patterns. An Arduino and Raspberry Pi work together to command the stepper motors to create various patterns in the sand.

Low-cost pine is used to build most of the table, with oak used for the attractive bare wooden top. RGB LEDs surround the sand surface in order to light the scene, with options for mad disco lighting or simple white light for a subtler look. Other nice touches include sitting the craft sand atop a layer of faux leather, so the ball moving through the sand doesn’t make annoying crunching sounds as the ball moves.

It’s a great build that focuses on the smaller details like noise that can make a big difference to the final experience. We’ve seen similar projects before, too. Video after the break.

Plastic waste is everywhere you look, and there’s seemingly no end in sight for both the demand and production of plastic goods. So isn’t it time to try putting all that waste from the plastic industry to good use? [Nzambi Matee], a materials engineer in Kenya, thinks so. She was tired of seeing plastic littering the streets of Nairobi, and saw an opportunity to solve two problems at once — cleaning up the streets and paving them with plastic.

Three years ago, [Nzambi] quit her job as an oil industry data analyst and used all her savings to pursue a solution for the pesky plastic problem. She built a lab in her mother’s backyard and begin experimenting with plastics and sand, melding them together to make blocks.

After about a year of trial and error, she had discovered which plastics worked and which didn’t. Then she developed machinery to churn out the sand-plastic paste and stamp it into sturdy paving bricks. Her company Gjenge Makers gets most of their plastic free from factories that would otherwise have to pay to dispose of it. The bricks are strong, lightweight, and nearly indestructible compared to concrete pavers. In the video after the break, there’s a shot of [Nzambi] spiking one on the ground to demonstrate its toughness.

Now, her company produces about 1,500 of these pavers each day. [Nzambi] and her team are planning to start making building blocks as well. With a melting point somewhere above 350° C, the material seems pretty well-suited for that purpose.

Want to do more than just recycle your plastic, but don’t know how? You could start by turning plastic bottles into rope, and then use the rope to make things like brooms and brushes.

Thanks for the tip, [foamyguy]!

[Ivan] seems to enjoy making 3D printed vehicles with tracks. His latest one uses 50 servo motors to draw patterns in the sand at the beach. You can see it work in the video below. Well, more accurately you can see it not work and then work as the first iteration didn’t go exactly as planned.

An Arduino Mega 2560 provides the brains and the whole unit weighs in at almost 31 pounds, including the batteries. We didn’t see Ivan’s design files, although it wouldn’t be hard to do your own take on the robot.

Speaking of the weight, we were amused at [Ivan’s] quick and dirty trailer he built to haul the thing around. We wondered if he had those wheels sitting around or if he had to source them from somewhere for this project.

The robot more or less moves in a straight line and the servos either drag a pointy part into the sand or lift the pointy part up so the sand is undisturbed in that area. The robot isn’t perfect. Not only did it not work the first time, but it also looked like it dropped at least one pointy part during the second test run. The tracks seemed to provide good traction, but we would not want to bet that the motion was completely straight.

On the other hand, it did get the job done. It was a lot of wiring and we suspect that’s why it was made all in one piece. Making it break down into sections would have been nice for transport. You might even be able to make it take a varying number of sections if you did it right. However, it would take a lot of connectors and a way for those connectors to support the weight of the beam, so that would be a much tougher problem.

We wish the design files were posted, but we still thought this was a neat enough idea and easy enough to figure out. We aren’t likely to build a 30-pound robot, but we might think about replicating it on a smaller scale to take to our local beach next summer.

We couldn’t help but remember Skryf, the robot that didn’t draw in the sand but drew with sand. Then there’s also  SandBot.