I T IS A little bit of magic. A gesture up and a seam comes together. A gesture down and a garment comes apart. The zip was one of the later fruits of the Industrial Revolution, and one that was slow to ripen: the internal combustion engine, the turbine and the light bulb spread across the world much faster. But the zip, too, has become ubiquitous—and in a much more intimate way. Those magic gestures have meaning.

In 2017 the global zip market was reckoned to be worth $11.2 billion, bigger than the market for condoms. It is predicted to reach $19.8 billion by 2024. It is not growing because of exciting new uses, just because of more luggage and clothes: a boom in cheap, disposable fashion and developing-world demand for Western-style clothing. But if consumption is global, the industry is not. Remarkably, up to 40% of the market, by value, may be controlled by one Japanese company: YKK , which makes more zips every year than there are people on the planet.

Eye eye

That the zip is relatively new, and was slow to spread, fits into the broader history of fastening. It is an arena where innovation has been slow and fitful—surpisingly so, perhaps, given peoples’ perennial need for clothes and luggage and their attachment to modesty and warmth. Take the button. As a decoration, it can be dated back almost 5,000 years, to what is now Pakistan. But for most of that time there were no buttonholes. Many societies held things together with loops and toggles, perhaps of horn. Others used buckles. The 11th-century Bayeux Tapestry shows men in cloaks pinned at the neck with brooches. Most people tied and wrapped.

Things got more interesting in Europe’s Middle Ages, a period more innovative than it is often given credit for. Laces started to make a strong showing in the 12th-century. They ran up the side of the bliaut, the sweeping garment worn by both men and women; they can be seen on the statues adorning Chartres Cathedral. In the 13th century, in Germany, the button at last met its hole. Then, in 14th-century Britain, the earliest ancestor of the zip showed up: the hook and eye. Their appeal lay in fastening two edges smoothly, with no need for them to overlap, as buttons require, or to be obviously laced. They were, and are, fiddly, flimsy little things, but those who could afford them could afford to have someone else do the fiddling for them, too. These days they survive mostly as point-to-point fastenings, sometimes above a zip, often on bras, a development for which women can thank, or remonstrate with, Mark Twain. The writer patented a hook-and-eye clasp on stretchy material in 1871.

It was in that same era of unparalleled American industrial creativity that the zip was first produced. Robert Friedel, who has written a history of the zip, calls it “an unlikely invention”. Thomas Edison’s light-bulb filament made the vital service of illumination both more powerful and, soon, much cheaper. Alexander Graham Bell’s telephone made something previously impossible possible. Though both had their belittlers, plenty of people saw the need for such things, and quickly seized on their potential. When it came to the world of fasteners, though, Mr Friedel notes, “there was no general sense that this was an area begging for improvement, much less replacement”.

The Universal Fastener Company of Chicago was built around an innovation by Whitcomb Judson, an oddball whose main obsession was developing a pneumatic streetcar driven by compressed air. He imagined using a sliding guide to pull together a line of hooks and a line of eyes on a boot, a notion that he patented in 1893. Alas, the two sides of Judson’s zip proved liable to come apart rather easily, defeating its purpose. Judson split, too, to further develop his no-more-successful streetcar.

The company was saved by Gideon Sundback, an immigrant engineer from Sweden. His developments were inspired, it is said, by two interleaved sets of soup spoons, stacked bowl on bowl but with their handles pointing alternately to one side and the other, and thus locked firmly together. Ignoring the company’s new name—the Automatic Hook and Eye Company—he ditched the hooks and eyes and replaced them with today’s design, more or less: two rows of metal protuberances with a tooth on one side and a socket on the other, forced together and prised apart by a puller. A similar design was patented by a Swiss woman named Katharina Kuhn-Moos around the same time, but it was never manufactured.

Sundback’s improved zip proved hard to market, not least because of the previous, dud design. It was used on utilitarian accessories—money belts, tobacco pouches—but the rag trade proved resistant. The first world war, though, gave the zip its break. In 1918, the US Navy began to put them on its aviator jackets. Then, in 1923, B.F. Goodrich, an American company best known for tyres, put zips on its rubber galoshes. It called the new footwear Zippers, thus giving the device—previously the “hookless fastener”—its name. (The British, for reasons unknown, changed the name to “zip”.)

But the device was still expensive, and this impeded its progress. When the company’s salesmen found New York dressmakers resistant to the zip’s charms, they invoked stereotypes of stingy Jews to explain their failure. But what businessman or woman would pay 35 cents for a zip for a one-dollar skirt when a button cost five cents?

The great unzipping

The resistance was not just about dollars and cents, though. It was also about what the zip represented: easy access; unfettered undoability. As late as the early 1930s it was seen as too strange and quite possibly too sexual to catch on, especially on women’s clothing. Aldous Huxley, in his novel “Brave New World”, published in 1931, realised that this could, regrettably, end up as a feature, not a bug. The inhabitants of his dystopian World State wore “zippicamiknicks” and “zippyjamas”, showing them simultaneously to be disturbingly modern and endlessly sexually available. As a later novelist, Tom Robbins, put it, “Zippers are primal and modern at the very same time. On the one hand, your zipper is primitive and reptilian, on the other mechanical and slick...Little alligators of ecstasy, that’s what zippers are.”

What Huxley looked on with distaste—modernity, mass production, copious and meaningless sex divorced from reproduction—sounded quite appealing to others. In 1930 Elsa Schiaparelli, an avant-garde designer, was the first dressmaker to feature prominent zips in her collections. Wallis Simpson, the lover and later wife of King Edward VIII, was a fan. The king’s subsequent adoption of the zipped fly is credited with its popularity in Britain, but young men were flocking to them everywhere. In 1940 a survey at Princeton University found the trousers of 85% of its students were zipped not buttoned. The class of 1894, by then in their 60s, still kept their flies buttoned almost to a man.

After the war, the zip took on a double life. It could be an ostentatious statement of toughness, rebellion, even danger. Think Marlon Brando in his leather jacket in “The Wild One” or, later, the zips which adorned the significantly less robust fashion of punk. But in dressmaking it functioned as a near absence, a slightly heavier seam which allowed clothing tighter than any since the days of corsets to be got into—and out of.

“I can never get a zipper to close,” Rita Hayworth says suggestively to her on-screen husband in “Gilda” (1946). “Maybe that stands for something. What do you think?” The way in which dress design made zipping and unzipping joint activities added to the zip’s frisson. And as Jess Cartner-Morley, a British fashion writer, points out, the post-war migration of the zip from the side of the dress to its back gave a “stark signal” about who was best placed for the unzipping. It wasn’t the wearer. In “Live and Let Die” (1973), Roger Moore, as James Bond, goes so far as to unzip a woman’s dress behind her back without even touching it, thanks to his handily magnetic watch. Seen this way, the barely noticeable zip reached its highest potential when it wasn’t even there at all. That is why the protagonist of Erica Jong’s novel “Fear of Flying”, published in 1973, calls the no-power-games, consummately easy, consummately pure sex she longs for “the zipless fuck”.

“I can never get a zipper to close—maybe that stands for something. What do you think?”

The tough and macho side and the sexual-access side of the zip could, naturally, fit together. Witness the real metal zip with which the denim crotch on the cover of the Rolling Stones’ album “Sticky Fingers” was adorned. Punk’s zips were as closely related to those of the fetish scene as they were to icons of the 1950s. If the sexiness of zips mostly lay in getting out of your clothes, for a minority it lay in getting into them—zips could do up garments of rubber or PVC deliciously tight.

There were still doubters, especially when it came to flies. Having metal teeth in delicate places is not without its worries. As Jerry Seinfeld, a comedian, once quipped, “It’s a mink trap down there.” Some felt buttons still made a statement. And some just worried about the zip’s reliability. Ronald Reagan said he would only ever wear a button fly because he was afraid of accidental openings—a reasonable concern for an actor and for a president.

Zipper-de-do-da

Once near universal, did the zip mutate into ever better forms fit for ever more markets? No. There have been innovations: plastic teeth to replace metal ones; the coil zip, using continuous spirals of nylon to form the teeth, making them more flexible and lightweight. But much of the focus has simply been on improving quality. Precision in zip manufacture is everything. Misalignment as thin as a piece of paper can cause jams. A broken zip, unlike a lost button, often leads to a garment being discarded.

The improvements have been almost exclusively led by YKK , which guarantees that each of its zips will last for 10,000 uses. Tadao Yoshida, “the zipper king”, founded the company in 1934, but had to start again after his Tokyo factory was bombed in the second world war. Soon the post-war company had gained a reputation for quality and reliability outside Japan. When Sundback’s patents expired in 1960, YKK expanded into America. Talon, the descendant of the original Universal Fastener Company, faded before the onslaught. As the garment industry moved offshore, the Japanese zips followed. The company now operates in 73 countries, with much of its production in China.

YKK has developed zips that are waterproof, heat resistant and that glow in the dark. The heart of Japanese business is the concept of kaizen, or continual improvement, and Hiroaki Otani, YKK ’s boss, says the company is investing heavily in R & D . But the improvements seem to be much more in process than in the product. What more is there for the zip to do? “Wouldn’t people like to do up a zip on the back of the dress with a touch on their smartphone?” offers Mr Otani, musingly. Leaving aside the risk of hackers, and James Bond’s colleague Q, it is not clear that this will become much of a market.

“If the main function has not changed, it is then about how to apply it in different circumstances and products,” says Patarapong Intarakumnerd, a professor of innovation in Tokyo. Some doctors, for example, speak longingly of a zip that can replace stitches after operations where they may need to access the same part of the patient’s body again. Radical innovation often comes from outside the dominant industry, points out Mr Intarakumnerd. Smartphones came from computer makers like Apple, not phone companies. Maybe some non-clothing, non-luggage industry will find a reason to reinvent and reimplement the zip.

Meanwhile, there are still bits of the wardrobe the zip has yet to conquer. Why, for example, are shirts still mostly buttoned, or even poppered, when they seem an obvious candidate for zipperdom? There is no clear answer, says Mr Friedel. He thinks fastenings “establish niches through customs, functionality, advertising and more, and then they become custom”.

And custom has, in this area, left the zip with very few rivals. Velcro, the most notable new fastening of the 20th century, inspired by the burrs of a plant, has limited appeal. It is used mainly for children and the elderly. It allows a range of fits, which is handy, particularly in footware. But it has its drawbacks; since the American army adopted it for uniforms in 2004, soldiers posted in dusty Iraq and Afghanistan have complained that it copes poorly with sand. And besides, there is not the beauty, the smooth, silent, sophisticated up-and-down of the zip.

And the zip does not really have to improve, or be replaced. Sometimes too much stress is put on progress. The technologies that matter most are not the ones around the corner. They are the ones in massive use. The zip was not born of radical new science or cunning craft, nor even of any deep need. Now that it is established, it says much less than it once did about sex, rebellion and modernity. It is unlikely to solve any of the world’s major problems. It was simply a clever way of making something a bit easier that happened to catch on. In that sense, it is like thousands of workaday inventions that shift from novelty to necessity, without much song and dance, and end up hard to better.