[Robert]: How does a zipper actually work? Like try to push down on a zipper from above and it probably won't budge, but if you just use the pull tab, suddenly it's buttery smooth. So how does it do this? We've made more zippers than there are stars in the Milky Way. You probably used one 10 times today without even noticing, except the only time you do is when one breaks. I'll show you what to do when this happens, but what is actually going on inside this thing? I mean, obviously the teeth come together inside the slider, but it turns out there is a surprising amount of engineering to this thing. All of this is too small to see on a real zipper, which is why we made this one. This is a video about the surprising genius of zippers. What is that? [Robert]: This is a device that basically started it all. The idea was just to take a bunch of hooks and eyes and try to put them together in some fashion to make them quote, "automatic", unquote.

[Gregor]: The hooks seemed very sharp, like I don't think I'd want this on my fly. [Robert]: No, no. Oh, definitely not there. (Robert laughing) [Robert]: By the 1800s, clothes were typically fastened using laces, buttons, brooches, and hooks and eyes. These got the job done, but they all shared the same flaw. If you had a series of these fasteners on a piece of clothing, well, you have to close them one by one. Most people were satisfied with the state of affairs, but one man, American engineer, Whitcomb Judson, thought the world deserved something better. [Robert]: The idea, primarily, it appears to be that he would put them in shoes and people who had to lace up would be able to do it in one quick motion. So that was the device that he had in mind, and it didn't work. [Robert]: Judson was a pretty bad inventor. Most of his patents had never gotten much traction, but he was a great salesman. In 1893 at the Chicago World's Fair, he presented this fastening device as the next big thing, claiming that in no time at all this would replace buttons and laces, and not just on shoes, but on all sorts of garments. A few wealthy investors actually believed it. So with their backing, the Universal Fastener Company was born. A decade later, the company managed to carve out a small niche, primarily selling its fasteners for women's skirts. "A pull and its done!" said their ads, but that was a lie. Judson's fastener design was a mess. It jammed constantly. And because it was delicate and made from rust prone steel, it actually had to be removed from the garment before you could wash it. So literally unsewn from your skirt. Moreover, if a single hook and eye were out of place, the whole fastener became unstable, so simply bend over and the whole thing could pop open. Naturally, the Universal Fastener Company had very few repeat customers, and they fell into debt.

[Robert]: But in 1906, a new engineer joined the team, 25-year-old Gideon Sundback, who had just moved to the US from Sweden. Why does someone like Gideon Sundback with a good degree in electrical engineering decide to join this failing company? [Gregor]: Well, it's a great story. [Robert]: See, one of the managers at the company had- [Robert]: An absolutely drop-dead gorgeous daughter. (Gregor chuckles) [Robert]: And that daughter came into the eye of Gideon Sundback, and he was completely smitten. So he ends up working for the fastener manufacturer so that he can cozy up to that daughter and they marry. [Gregor]: For the next few years, Sundback made minor improvements to Judson's hook and eye design, but none were ever enough to make the product truly functional. Then soon after giving birth to a daughter, his wife Elvira, fell ill and died. [Robert]: And Sundback was absolutely devastated. So the romantic tale is that he threw himself into his work at that point out of fighting the grief from the loss of his wife. [Robert]: This dark period in his life led to a major breakthrough. Sundback realized that this (paper crinkling) was never gonna work. So after years of tinkering, he submitted a patent of his own. This is a patent from 1914, but if you take a look, it is nearly identical to a zipper from today.

[Robert]: Sundback's modern zipper starts with two rows of teeth, and the teeth are shaped so that they're wider at the end than the opening on the other side. So if you try to push them together, it's pretty hard. Now, this is especially true on a real size zipper where it's practically impossible. But if I add this slider to the bottom and try pulling on the pull tab here, suddenly it's effortless. So how does it do it? Well, I can remove the cover from the slider to reveal that it's just a Y-shaped cavity. That's it. See, as you zip up, the Y-shaped cavity tilts the teeth at just the right angle so that the tooth has enough space to slot into its groove without bumping into the tooth above. And as you zip down, this wedge shaped piece separates the teeth, allowing you to unzip. This results in one awkward design quirk. At the top, no zipper is ever fully zipped up because the wedge is always there. It has to remain between the teeth. Now, Sundback's original design was a little different to this big guy. It sported rectangular teeth with a bump on the top called the nib, and an equivalently shaped indent on the bottom called the scoop. That way, when the teeth would align, each nib would fit neatly into its neighbor's scoop, forming a strong connection. But there was a problem, even though Sundback had a new design and a patent, manufacturing a zipper like this in the 1910s was very impractical. Each of the tiny teeth needed to be precisely shaped for the fastener to work, but at the time, there were simply no tools around that could do this reliably.

[Robert]: So he had to come up with some extraordinarily clever machineries that allowed them to automate the production of the zipper from the very beginning. [Robert]: Sundback's machine worked like this. It took Y-shaped wire made from a nickel alloy as an input. First, it sliced pieces off the wire to serve as individual teeth, and then it stamped the scoop and nib into each tooth. Finally, the machine would clamp the two arms of the Y-shape together onto a piece of fabric called the tape. This tape held all the teeth in place, and it was the part of the zipper that would later get stitched onto clothes and other products. [Robert]: Sundback's machines worked wonders. Even in their earliest forms, they could already make 150 meters of zippers per day, and these zippers were incredibly strong. That's because for a tooth to become unpaired, it needs to get some distance between itself, and its neighbors, enough for the nibs on either side to pop out. But since the machines spaced the teeth so precisely, there was simply no room for that to happen. Now, you might think you could just stretch the zipper vertically to separate the teeth, but the zipper tape itself is made from strong inelastic fabric. So even if the garment itself is stretchy, the teeth are connected to the tape which is designed not to stretch, so they won't come loose. But there is a way for this mechanism to fail. If even a single tooth falls off, well, then its neighbors have enough space to come loose, and then their neighbors come loose, and this causes a cascading effect, and the whole zipper pops open. This isn't something you had to worry about with buttons, which can only fail one at a time. But even with this flaw, Sundback's employers thought this patent was a gold mine.

[Robert]: So the Universal Fastener Company decided to launch the product under their new name, 'The Hookless Hooker'. They abandoned that name pretty quickly and decided to call it 'The Hookless Fastener' instead. This new fastener was a successful product, but not a mainstream one. Its first applications were pretty niche. You'd find it on money belts, essentially the fanny packs of the 1910s, as well as tobacco pouches and rubber boots. Now, those rubber boots were particularly important. They were manufactured by the B.F. Goodrich Company. [Robert]: When they got a hold of the device, they were convinced that, yes, this will give us a leg up on our competitor. We will introduce this automatic fastener, but we need a name for it. [Gregor]: Then the company's president had an idea. [Robert]: Well, you know, it worked really well. They're pretty nice. You can just sort of... It just goes sort of zip when you're closing it and when you're opening it. So, B.F. Goodrich came out in the early 1920s with their zipper boots. [Robert]: The boots were such a hit that the name zipper transcended the shoe and became the name for the fastener itself. Soon, consumers wanted the zipper on everything.

[Robert]: By the 1930s, the Universal Fastener Company became very, very successful. They got a new name, too: Talon, since their fasteners had a secure grip, it was kind of like the talons of an eagle. Talon's new zippers were way sturdier than Judson's hook and eye design, because their parts were way simpler, and they were also made out of rust resistant nickel alloy instead of steel, which meant you could leave them on in the wash. By the way, if you are putting something with a zipper inside the washing machine, you should always zip it up. That will prevent the zipper from snagging on your other clothes, and it'll also protect the zipper itself. Now, even though zippers rapidly became popular, there was pushback among the older and more conservative consumers, especially about putting them on the fly. And urban legends began to spread. [Robert]: One of the most famous ones is the myth of the fellow who has come to his fiance's parents for dinner, he's seated down at the table, he looked down and realized, "Oh my God, I haven't zipped up my fly," so he zips it up. But then when he gets up a few minutes later to leave the table, he has caught the tablecloth in the fly of his trousers, and so ends up sending the entire table tumbling after him as he gets up and leaves. [Robert]: I'm still a bit confused by... zippers are more expensive, more temperamental than buttons and laces, and anyways, they become huge regardless of that. [Robert]: Well, now you see the heart of the mystery. The novelty of a zipper itself was something that took hold of people. People wanted to be modern, and it came to be closely identified with being modern. I found it very interesting that looking at World War II, the zipper manufacturer in Germany was one of the protected industries, despite the fact that it used fairly precious metal, metals that were very important for munition and the like. But the zippers were protected because they were closely identified with modern prosperity, with the idea that if we can have zippers then everything must be okay.

[Robert]: But a more obvious reason for the zipper's popularity is that it's just so easy to use. How much quicker is a zipper than a series of buttons? I have a jacket that has both, so let's time it. Three, two, one. There we go. I mean, it's a pretty great example of how a more automatic approach can save you a bunch of time, which is what today's sponsor Hostinger is all about. Say you have a bunch of projects spread out over Slack, and email, and WhatsApp. If you're trying to keep track of everything manually, it's a pretty slow process, and it's super easy to miss something. But with Hostinger and their virtual private server or VPS, you can quickly zip up your entire project and bring everything together in one place. In just a single click, a Hostinger VPS lets you deploy OpenClaw, which is a multi-channel personal assistant. And OpenClaw's declutter feature will go through all of your inboxes and pluck out all the most important messages and zip them together into one central hub. It's also a great research tool, so if there's a topic you're interested in, you can use OpenClaw to scrape the web for relevant sources, and also keep up to date on posts everywhere from Reddit to Nature. And because it runs 24/7, you can wake up each morning to a fresh batch of articles delivered straight to your inbox. So if you're interested in running OpenClaw, head to hostinger.com/veritasiumopenclaw, or click on the link in the description, and make sure you use code Veritasium to get an exclusive discount on all yearly VPS plans. So I wanna thank Hostinger for sponsoring this part of the video. And now back to zippers.

[Robert]: Fast forward to today, Sundback's design is still the one we most associate with zippers. Besides the classic metal variant, which was sturdy and reliable, zippers also started being produced from plastic, which was cheaper and more flexible. But you'd probably be surprised to know that these two zipper types aren't the most common zipper in the world. In fact, the world's most popular zipper doesn't have teeth at all, and it's this thing. (dramatic music) Okay, at first it just looks like other zippers, but if I pull out the threads, you can see that everything here is just a single weird piece of plastic. Imagine you have a coil of plastic that you somewhat flatten. You can mold the plastic such that one side of every loop bulges out more on the top and bottom. If you do this a second time with a second piece of plastic, you'll notice that you now have ridges that fit perfectly together, much like zipper teeth. Stitch these two coils onto fabric, then add a slider, and bam, you have a functional zipper. This is known as a coil zipper. It showed up around the 1940s as a cheap alternative to the original design, and now you can find it everywhere, especially on things like suitcases and backpacks where the zipper needs flexibility to maneuver around corners. Coil zippers also have another benefit. Since all of their teeth are one interconnected piece of plastic, there's no way for a single tooth to fall off, so that itself cannot cause that cascading failure.

[Robert]: But there was still a problem zippers had to solve, and that was that they were kind of too good, especially zippers that have been used a lot and are kind of worn down in the slider, they can... just unzip on their own. To prevent that, Gideon Sundback himself actually designed a locking mechanism like a break. Under the piece that connects the pull tab to the slider, there is a small metal pin. When the pull tab is in its typical resting position, one end of the pin sticks through a hole in the bottom face of the slider, lodging itself between the zipper's teeth or coils. That way the slider is stuck in place. But when the pull tab is pulled forward, this releases the pin, allowing the slider to move. Now you can see that there's like this little tiny gap through which you can see light, and that's because the zipper stop is now engaged. But if I grab the pull tab and start pulling, you can see that because of the way that it's shaped, it's actually gonna end up pushing that part up, even though I'm pulling to the side, and that's gonna disengage. You can try to pull apart the fly on your pants, but unless you actually grab the pull tab and pull it down, it is not gonna open. These locking mechanisms aren't on every zipper, but they're more common than you might think. I counted up 65 zippers in this room in total, 33 of those 65 had stopping mechanisms, which is over 50%. Which is also something I never noticed on a zipper. But as I was hunting for zippers in my room. I noticed something else, on pull tab after pull tab there's no mention of Talon, but I kept finding the same three letters instead: YKK, YKK, YKK. YKK. Even on clothes and objects from completely different brands. If you look at your zipper now, you'll probably see the same thing. So at first, I thought this might refer to a particular style of zipper or something, but then I Googled it, and it turns out that YKK is a company, the biggest zipper company in the world.

[Robert]: If Talon has the original patent rights and they own the original zipper, how don't I have a single Talon zipper in my room, and how did YKK end up dominating the zipper world? Well, Talon pretty much ruled the zipper market until the 1930s, but in 1934, Sundback's original patent expired, so the playing field was wide open to competitors. That same year, Japanese businessman, Tadao Yoshida, founded a new fastener company, the Yoshida Manufacturing Corporation, or YKK. It began as a single workshop in Tokyo where each zipper was made by hand. Then in 1945, that workshop was completely destroyed by allied bombs, but Yoshida was undaunted. He rebuilt the plant, and after the war, he started buying zipper making machines from the US. [Robert]: They improved the machine, particularly they improved the speed. [Gregor]: They then also decided to switch to manufacturing everything in-house from the zippers themselves to the machines, to even the boxes that the zippers were shipped in. [Robert]: And YKK emphasizes quality above everything else. So they make a real point of saying that if you have a YKK zipper, you can depend on it utterly. And that turned out to be an enormously successful sale tactic. [Gregor]: Around 1980, YKK surpassed Talon as the world's biggest zipper maker, and by the early 2000s, Talon's US market share had fallen to a mere 7%, while YKK's surged to around 45%. [Robert]: YKK surpassed the 10 billion annual zipper unit sales last year. [Robert]: I mean, that's a very impressive number. Like 10 billion is crazy. [Robert]: It's equivalent to more than 3 million kilometers in length. It could be like around like 80 trips around the world. [Gregor]: And not all of these are regular everyday zippers either.

[Robert]: So this is an airtight, watertight zipper, and this relies on rigid metal to metal sealing, where nickel teeth are forced tightly together against a rubber tape providing an extreme pressure resistance. [Robert]: I mean, that looks like a mean zipper. What's an extreme use case for a zipper like this? [Robert]: Deep sea diving, submarine escape suits. [Robert]: Submarine escape suits sound really cool. In case of an emergency evacuation of a submarine, you need a suit that can balloon up with air to counteract the pressure of the deep ocean, and that can provide buoyancy helping you shoot up to the surface. But you also need to be able to put it on super quickly. And the best option seems to be this suit with a giant watertight and airtight zipper on the front. Airtight zippers like these even made it onto spacesuits. And that's the zipper. It's this surprisingly genius invention that no one really asked for.

[Robert]: I hate when this happens. [Robert]: I think a zipper slider may get stuck if fabric becomes caught in the chain. So if dirt or debris enters in the zipper, the best fix is to carefully remove any trapped fabric or debris, or move the slider gently. [Robert]: Okay, so carefully removing stuff from the zipper. [Robert]: Yeah, yeah. [Robert]: Because my first reaction is just like, try and jam over the slider. So you're saying I shouldn't do that? [Robert]: Yeah, no. Move it carefully. [Robert]: Carefully! [Robert]: And if there isn't any visible debris causing the zipper to get stuck, you can try lubricating the area with graphite from a pencil in order to get the slider moving again, because it's a great dry lubricant. But probably the most annoying zipper problem is when a zipper unzips on both sides of the slider. [Robert]: This usually happens when the slider becomes worn or bent, and can no longer apply enough pressure to properly interlock the zipper elements as a result. So the zipper chain separates behind the slider. [Robert]: A worn down slider is something you might be able to fix at home. Just take some pliers and crimp the slider together from the sides. That will make the inner cavity more narrow, just like when it was new, which should make it bring the teeth together again. Just don't crimp it too tightly.

[Robert]: I just can't get over the fact that the first patent Gideon Sundback submitted was around 1914, and in those 112 years so many other devices that we've invented have been completely transformed, got better, got faster, cheaper, but it seems like the zipper is mostly just the same. So it's just that Sundback's design was that good? [Robert]: It's that good. (Robert laughing) [Robert]: I don't have any better explanation. It really is. It's that good.