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What Are Loofahs Made Of?

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Bath time, spa experiences, and even common household chores just wouldn't be the same without the humble sponge. Sponges, mostly from class Demospongiae, have been sold commercially as cleansing aids for thousands of years, and have also been used as water filters, padding for soldiers’ helmets, and for painting and decorating. (The brightly-colored pad hanging out by your kitchen sink right now is, of course, a synthetic design modeled after nature's handy tool.)

Although natural loofahs resemble their bathroom counterparts, they're actually about as unrelated as it’s possible to be. The loofah you scrub with is a dried-out tropical or subtropical gourd belonging to genus Luffa (most often either species L. aegyptiaca or L. acutangula). And while no one is completely sure where it originated—as W.M. Porterfield wrote in a 1955 Economic Botany article: "[c]ultivation of the sponge gourd is of such ancient origin that it is impossible to determine whether the original home was in Africa or Asia” [PDF]— a study in 1990 indicated that it was probably first cultivated in India. These plants—which look a bit like giant cucumbers—grow year-round in almost any tropical climate and places that have warm seasons, so long as there is plenty of moisture and no risk of frost.


Like sponges, the fibrous dried luffa has likely been used in Egypt and Asia for up to a couple thousand years. But its biggest boost as a cleansing tool began in the early 1890s, when Japan started cultivating commercial luffa crops for international export. (Prior to that, luffas were mostly used when a thorough household scrubbing was in order.) Word spread about the exfoliating item just as bathing suits and hemlines began retreating in the late 19th and early 20th centuries, according to The New York Times Magazine, which left many women with newfound anxiety about the smoothness of their skin. Inventions like the Improved Bathing Mitten, patented in 1889 by Judson S. Snyder of Brooklyn, New York, transformed the large gourds into easier-to-handle versions. By 1893, “no one seemed able to agree on how to spell the name of that sponge, but it inspired such a craze [that one] expected to see ‘a ‘loafer,’ ‘luphar,’ a ‘loopa’ or a ‘loofah’ in every wash basin the land,'” according to that same New York Times Magazine article.

But cleaning isn't all they're good for. According to Porterfield, commercial cultivation of the plant in the 1890s also let luffas fill a wide range of industrial roles. Before the second World War, over half of imported luffa goards were used in filters (chiefly in the Navy) for everything from steam to diesel engines. They also found use as water filters, industrial scourers, and even surgical tools. After wartime conflict drove Western powers to start sourcing their luffa shipments elsewhere, the dried veggies continued to prove useful through the mid-20th century as an effective sound-proofing material for tanks, helmets, and certain kinds of buildings.

When man-made materials began taking over many industrial roles in the 20th century, the noble luffa was mostly returned to its role as a cleaning tool—and, of course, a popular food, one that easily stands in for cucumbers or summer squash while it’s still immature. The vine is so easy to grow that it has been floated as a candidate for a profitable, sustainable crop to help drive economic and agricultural development here in the U.S. as well as countries like Paraguay [PDF]. Because they’re so resilient, luffa vines can be easily grown by amateur gardeners in much of the country (apart from the upper Midwest and New England), so feel free to take a whack at rearing this useful gourd—just make sure that any luffas that find a place in your bathroom don’t end up being a farm for bacteria themselves.

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iStock // Ekaterina Minaeva
Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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200 Health Experts Call for Ban on Two Antibacterial Chemicals
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In September 2016, the U.S. Food and Drug Administration (FDA) issued a ban on antibacterial soap and body wash. But a large collective of scientists and medical professionals says the agency should have done more to stop the spread of harmful chemicals into our bodies and environment, most notably the antimicrobials triclosan and triclocarban. They published their recommendations in the journal Environmental Health Perspectives.

The 2016 report from the FDA concluded that 19 of the most commonly used antimicrobial ingredients are no more effective than ordinary soap and water, and forbade their use in soap and body wash.

"Customers may think added antimicrobials are a way to reduce infections, but in most products there is no evidence that they do," Ted Schettler, science director of the Science and Environmental Health Network, said in a statement.

Studies have shown that these chemicals may actually do more harm than good. They don't keep us from getting sick, but they can contribute to the development of antibiotic-resistant bacteria, also known as superbugs. Triclosan and triclocarban can also damage our hormones and immune systems.

And while they may no longer be appearing on our bathroom sinks or shower shelves, they're still all around us. They've leached into the environment from years of use. They're also still being added to a staggering array of consumer products, as companies create "antibacterial" clothing, toys, yoga mats, paint, food storage containers, electronics, doorknobs, and countertops.

The authors of the new consensus statement say it's time for that to stop.

"We must develop better alternatives and prevent unneeded exposures to antimicrobial chemicals," Rolf Haden of the University of Arizona said in the statement. Haden researches where mass-produced chemicals wind up in the environment.

The statement notes that many manufacturers have simply replaced the banned chemicals with others. "I was happy that the FDA finally acted to remove these chemicals from soaps," said Arlene Blum, executive director of the Green Science Policy Institute. "But I was dismayed to discover at my local drugstore that most products now contain substitutes that may be worse."

Blum, Haden, Schettler, and their colleagues "urge scientists, governments, chemical and product manufacturers, purchasing organizations, retailers, and consumers" to avoid antimicrobial chemicals outside of medical settings. "Where antimicrobials are necessary," they write, we should "use safer alternatives that are not persistent and pose no risk to humans or ecosystems."

They recommend that manufacturers label any products containing antimicrobial chemicals so that consumers can avoid them, and they call for further research into the impacts of these compounds on us and our planet.