Zipper

Background

Fasteners have come a long way since the early bone or horn pins and bone splinters. Many devices were designed later that were more efficient; such fasteners included buckles, laces, safety pins, and buttons. Buttons with buttonholes, while still an important practical method of closure even today, had their difficulties. Zippers were first conceived to replace the irritating nineteenth century practice of having to button up to forty tiny buttons on each shoe of the time.

In 1851, Elias Howe, the inventor of the sewing machine, developed what he called an automatic continuous clothing closure. It consisted of a series of clasps united by a connecting cord running or sliding upon ribs. Despite the potential of this ingenious breakthrough, the invention was never marketed.

Another inventor, Whitcomb L. Judson, came up with the idea of a slide fastener, which he patented in 1893. Judson's mechanism was an arrangement of hooks and eyes with a slide clasp that would connect them. After Judson displayed the new clasp lockers at the 1893 World's Columbian Exposition in Chicago, he obtained financial backing from Lewis Walker, and together they founded the Universal Fastener Company in 1894.

The first zippers were not much of an improvement over simpler buttons, and innovations came slowly over the next decade. Judson invented a zipper that would part completely (like the zippers found on today's jackets), and he discovered it was better to clamp the teeth directly onto a cloth tape that could be sewn into a garment, rather than have the teeth themselves sewn into the garment.

Zippers were still subject to popping open and sticking as late as 1906, when Otto Frederick Gideon Sundback joined Judson's company, then called the Automatic Hook and Eye Company. His patent for Plako in 1913 is considered to be the beginning of the modern zipper. His "Hookless Number One," a device in which jaws clamped down on beads, was quickly replaced by "Hookless Number Two", which was very similar to modern zippers. Nested, cup-shaped teeth formed the best zipper to date, and a machine that could stamp out the metal in one process made marketing the new fastener feasible.

The first zippers were introduced for use in World War I as fasteners for soldiers' money belts, flying suits, and life-vests. Because of war shortages, Sundback developed a new machine that used only about 40 percent of the metal required by older machines.

Zippers for the general public were not produced until the 1920s, when B. F. Goodrich requested some for use in its company galoshes. It was Goodrich's president, Bertram G. Work, who came up with the word zipper, but he wanted it to refer to the boots themselves, and not the device that fastened them, which he felt was more properly called a slide fastener.

The next change zippers underwent was also precipitated by a war—World War II. Zipper factories in Germany had been destroyed, and metal was scarce. A West German company, Opti-Werk GmbH, began research into new plastics, and this research resulted in numerous patents. J. R. Ruhrman and his associates were granted a German patent for developing a plastic ladder chain. Alden W. Hanson, in 1940, devised a method that allowed a plastic coil to be sewn into the zipper's cloth. This was followed by a notched plastic wire, developed independently by A. Gerbach and the firm William Prym-Wencie, that could actually be woven into the cloth.

After a slow start, it was not long before zipper sales soared. In 1917, 24,000 zippers were sold; in 1934, the number had risen to 60 million. Today zippers are easily produced and sold in the billions, for everything from blue jeans to sleeping bags.

Raw Materials

The basic elements of a zipper are: the stringer (the tape and teeth assembly that makes up one side of a zipper); the slider (opens and closes the zipper); a tab (pulled to move the slider); and stops (prevent the slider from leaving the chain). A separating zipper, instead of a bottom stop that connects the stringers, has two devices—a box and a pin—that function as stops when put together.

Metal zipper hardware can be made of stainless steel, aluminum, brass, zinc, or a nickel-silver alloy. Sometimes a steel zipper will be coated with brass or zinc, or it might be painted to match the color of the cloth tape or garment. Zippers with plastic hardware are made from polyester or nylon, while the slider and pull tab are usually made from steel or zinc. The cloth tapes are either made from cotton, polyester, or a blend of both. For zippers that open on both ends, the ends are not usually sewn into a garment, so that they are hidden as they are when a zipper is made to open at only one end. These zippers are strengthened using a strong cotton tape (that has been reinforced with nylon) applied to the ends to prevent fraying.

The Manufacturing
Process

Today's zippers comprise key components of either metal or plastic. Beyond this one very important difference, the steps involved in producing the finished product are essentially the same.

Making stringers—metal zippers

• 1 A stringer consists of the tape (or cloth) and teeth that make up one side of the zipper. The oldest process for making the stringers for a metal zipper is that process invented by Otto Sundback in 1923. A round wire is sent through a rolling mill, shaping it into a Y-shape. This wire is then sliced to form a tooth whose width is appropriate for the type of zipper desired. The tooth is then put into a slot on a rotating turntable to be punched into the shape of a scoop by a die. The turntable is rotated 90 degrees, and another tooth is fed into the slot. After another 90 degrees turn, the first tooth is clamped onto the cloth tape. The tape must be raised slightly over twice the thickness of the scoop—the cupped tooth—after clamping to allow room for the opposite tooth on the completed zipper. A slow and tedious process, its popularity has waned.

  Another similar method originated in the 1940s. This entails a flattened strip of wire passing between a heading punch and a pocket punch to form scoops. A blanking punch cuts around the scoops to form a Y shape. The legs of the Y are then clamped around the cloth tape. This method proved to be faster and more effective than Sundback' s original.

• 2 Yet another method, developed in the 1930s, uses molten metal to form teeth. A mold, shaped like a chain of teeth, is clamped around the cloth tape. Molten zinc under pressure is then injected into the mold. Water cools the mold, which then releases the shaped teeth. Any residue is trimmed.

Making stringers—plastic zippers

• 3 Plastic zippers can be spiral, toothed, ladder, or woven directly into the fabric. Two methods are used to make the stringers for a spiral plastic zipper. The first involves notching a round plastic wire before feeding it between two heated screws. These screws, one rotating clockwise, the other counter-clockwise, pull the plastic wire out to form loops. A head maker at the front of each loop then forms it into a round knob. Next, the plastic spiral is cooled with air. This method requires that a left spiral and right spiral be made simultaneously on two separate machines so that the chains will match up on a finished zipper.

  The second method for spiral plastic zippers makes both the left and right spiral simultaneously on one machine. A piece of wire is looped twice between notches on a rotating forming wheel. A pusher and head maker simultaneously press the plastic wires firmly into the notches and form the heads. This process makes two chains that are already linked together to be sewn onto two cloth tapes.

• 4 To make the stringers for a toothed plastic zipper, a molding process is used that is similar to the metal process described in step #2 above. A rotating wheel has on its edge several small molds that are shaped like flattened teeth. Two cords run through the molds to connect the finished teeth together. Semi-molten plastic is fed into the mold, where it is held until it solidifies. A folding machine bends the teeth into a U-shape that can be sewn onto a cloth tape.
• 5 The stringers for a ladder plastic zipper are made by winding a plastic wire onto alternating spools that protrude from the edge of a rotating forming wheel. Strippers on each side lift the loops off the spools while a heading and notching wheel simultaneously presses the loops into a U shape and forms heads on the teeth, which are then sewn onto the cloth tape.
• 6 Superior garment zippers can be made by weaving the plastic wire directly into the cloth, using the same method as is used in cloth weaving. This method is not common in the United States, but such zippers are frequently imported.

Completing the manufacturing
process

• 7 Once the individual stringers have been made, they are first joined together with a temporary device similar to a slider. They are then pressed, and, in the case of metal zippers, wire brushes scrub down sharp edges. The tapes are then starched, wrung out, and dried. Metal zippers are then waxed for smooth operation, and both types are rolled onto huge spools to be formed later into complete zippers.
• 8 The slider and pull tab are assembled separately after being stamped or die-cast from metal. The continuous zipper tape is then unrolled from its spool and its teeth are removed at intervals, leaving spaces that surround smaller chains. For zippers that only open on one end, the bottom stop is first clamped on, and then the slider is threaded onto the chain. Next, the top stops are clamped on, and the gaps between lengths of teeth are cut at midpoint. For zippers that separate, the midpoint of each gap is coated with reinforcing tape, and the top stops are clamped on. The tape is then sliced to separate the strips of chain again. The slider and the box are then slipped onto one chain, and the pin is slipped onto the other.
• 9 Finished zippers are stacked, placed in boxes, and trucked to clothing manufacturers, luggage manufacturers, or any of the other manufacturers that rely on zippers. Some are also shipped to department stores or fabric shops for direct purchase by the consumer.

Quality Control

Zippers, despite their numbers and practically worry-free use, are complicated devices that rely on a smooth, almost perfect linkage of tiny cupped teeth. Because they are usually designed to be fasteners for garments, they must also undergo a series of tests similar to those for clothing that undergo frequent laundering and wear.

A smoothly functioning zipper every time is the goal of zipper manufacturers, and such reliability is necessarily dependent on tolerances. Every dimension of a zipper—its width, length, tape end lengths, teeth dimensions, length of chain, slide dimensions, and stop lengths, to name a few—is subject to scrutiny that ascertains that values fall within an acceptable range. Samplers use statistical analysis to check the range of a batch of zippers. Generally, the dimensions of the zipper must be within 90 percent of the desired length, though in most cases it is closer to 99 percent.

A zipper is tested for flatness and straightness. Flatness is measured by passing a gauge set at a certain height over it; if the gauge touches the zipper several times, the zipper is defective. To measure straightness, the zipper is laid across a straight edge and scrutinized for any curving.

Zipper strength is important. This means that the teeth should not come off easily, nor should the zipper be easy to break. To test for strength, a tensile testing machine is attached by a hook to a tooth. The machine is then pulled, and a gauge measures at what force the tooth separates from the cloth. These same tensile testing machines are used to test the strength of the entire zipper. A machine is attached to each cloth tape, then pulled. The force required to pull the zipper completely apart into two separate pieces is measured. Acceptable strength values are determined according to what type of zipper is being made: a heavy-duty zipper will require higher values than a lightweight one. Zippers are also compressed to see when they break.

To measure a zipper for ease of zipping, a tensile testing machine measures the force needed to zip it up and down. For garments, this value should be quite low, so that the average person can zip with ease and so that the garment material does not tear. For other purposes, such as mattress covers, the force can be higher.

A finished sample zipper must meet textile quality controls. It is tested for laundering durability by being washed in a small amount of hot water, a significant amount of bleach, and abrasives to simulate many washings. Zippers are also agitated with small steel balls to test the zipper coating for abrasion.

The cloth of the zipper tapes must be colorfast for the care instructions of the garment. For example, if the garment is to be dry cleaned only, its zipper must be colorfast during dry cleaning.

Shrinkage is also tested. Two marks are made on the cloth tape. After the zipper is heated or washed, the change in length between the two marks is measured. Heavyweight zippers should have no shrinkage. A lightweight zipper should have a one to four percent shrinkage rate.

Where To Learn More

Books

Petroski, Henry. The Evolution of Useful Things. Knopf, 1992.

Zipper! An Exploration in Novelty. W. W. Norton & Co., Inc., 1994.

Periodicals

Berendt, John. "The Zipper," Esquire. May, 1989, p. 42.

Getchell, Dave. "Zip It Up: How to Care For and Repair Zippers," Backpacker. May, 1993, p. 94.

Kraar, Louis. "Japanese Pick Up U.S. Ideas," Fortune, Spring-Summer, 1991, p. 66.

"Zip," The New Yorker. December 17, 1979, pp. 33-34.

Weiner, Lewis. "The Slide Fastener," Scientific American. June, 1983, pp. 132-144.

—Rose Secrest

ZIPPER

More generically called a "slide fastener," the zipper is used as a closure in garments and a variety of other articles. Zippers were first introduced in a primitive form in the 1890s, but were not widely accepted in clothing until the 1930s.

The fastener that Americans most commonly call "zippers" can be traced to the invention of a Midwestern traveling salesman, Whitcomb Judson, in the early 1890s. Judson patented his device as a "clasp locker or unlocker" for shoes; this invention resembled the later zipper only superficially. It consisted of a series of hooks and eyes, each pair of which was engaged by the action of a key or slider. Over the next few years, Judson designed modifications of this device, none of which worked very effectively. The idea of an "automatic hook-and-eye," however, caught the attention of entrepreneurs, so Judson was given money and encouragement to continue engineering his invention, and in the first years after 1900, the first devices came to market under the aegis of the Universal Fastener Company of Hoboken, New Jersey.

After several years of futile design and sales efforts, the Hoboken company gained the services of a Swedish immigrant, Gideon Sundback. Trained as an electrical engineer, Sundback was a remarkably clever and astute mechanic. He analyzed with care the key elements of the automatic hook-and-eye, and concluded that the hook-and-eye model was not a suitable one for any kind of automatic fastener. Late in 1913, Sundback introduced his "Hookless Fastener," based on novel principles and resembling in all important respects the modern metal zipper.

Sundback's hookless fastener depended on the action of a series of closely spaced elements, technically called "scoops," whose precise spacing and ingenious shape are key to the fastener's success. Each scoop has a dimple on one side and a protruding nib on the other. The fastener consists of two opposing rows of scoops, spaced so that the scoops from one side engage in the spaces between the scoops on the other side. The nib from one scoop fits into the dimple in the facing scoop, whose nib in turn fits into the next dimple down the row. Sundback likened the action to a series of spoons in which the bowls of alternating spoons fitted into one another. If the spoons at each end of the rows are held in place, the intermediate spoons cannot disengage one another. The slider's function is simply to bring the two rows of scoops together (or to separate them) in a continuous, serial action.

The entrepreneurs who had backed Judson and then Sundback readily saw the efficacy of the hookless fastener design. Sundback's contributions went further to include the construction of machinery that made fastener manufacture rapid and economical. The Hookless Fastener Company was organized in Meadville, Pennsylvania, and efforts to market the novel device began in 1914. The fastener makers encountered challenges every bit as formidable as the technical ones they had overcome after such effort. The early hookless fastener was an unquestionably clever device, and it worked reasonably reliably and consistently. It was, however, expensive compared to the buttons or hooks and eyes that it was designed to replace, and it posed a host of difficulties for the designers and makers of most garments.

The clothing industry initially rejected the new fastener. It might, in fact, have died an ignominious early death if its salesmen had not cultivated small niche markets that sustained it for several years. Money belts for World War I sailors were followed by tobacco pouches, which in turn were followed, in the early 1920s, by rubber overshoes. The manufacturers of this last, the B. F. Goodrich Rubber Company, came up with a moniker for their new product, "Zippers," that became even more popular than the overshoes themselves, and the term "zipper" came to be the common American term for the fastener (despite Goodrich's trademark claims). Through most of the 1920s, expanding niche markets brought the fastener to a wider public, although garment makers still resisted wider adoption. Hookless Fastener adopted the trademark "Talon" in 1928 (and changed the corporate name to Talon, Inc., a decade later).

Only in the 1930s did zippers come to be accepted elements of men's and women's clothing, and even then only by steps. The famous haute couture designer, Elsa Schiaparelli, chose to set her designs of 1935 off by liberal use of zippers—even in places where no fastener was needed or expected. A couple of years later, in 1937, zippers began to appear widely in high fashion lines— Edward Molyneux's pencil-slim coats, for example, used zippers to emphasize the sleek silhouette. At about the same time, the designers of the best tailored men's clothing let it be known that zippered flies were acceptable, and by the end of the decade, zippers were common in the better men's trousers and were making their way into the ready-to-wear market. The combination of a reduction in prices (due to higher volume production) and the growing association of the zipper with modernity and fashion overcame the long-standing resistance of the garment makers and buyers. The widespread use of zippers in military uniforms during World War II was associated by many with the final popularization of the fastener, but its usage was already well on its way to becoming common before the war. By the 1950s, the zipper was the default fastener for everything from skirt plackets and trouser flies to leather motorcycle jackets and backpacks.

Even before the war, some manufacturers experimented with replacing the copper-nickel alloy standard in zippers with plastic, but this substitution was not very successful until Talon and the DuPont Company collaborated on a very new zipper design, in which the metal scoops were replaced by nylon spirals. The nylon zipper, after a few difficult years, became the standard appliance for lightweight applications, as garment makers were particularly attracted to the ease with which the nylon could be colored to match fabric dyes. Other materials were used for more specialized purposes: surgeons even adopted inert Teflon zippers for post-operative applications.

The zipper was by no means a strictly American phenomenon. Within only a few years of its introduction, British manufacturers sought to establish manufacture, and by the mid-1920s, French, German, and other suppliers followed. The chief British manufacturer, the Lightning Fastener Company of Birmingham, gave its name to the fastener itself in a wide range of languages; in France it became known as a "fermature éclair," and in Germany as a "Blitzverschluss" (Reissverschluss became the more common German word later).

As the zipper became increasingly common in the twentieth century, it acquired an unusual cultural status. It became a widely recognized and used symbol with a host of associations. Aldous Huxley used zippers throughout his 1932 novel, Brave New World, to allude to the impersonal and mechanical nature of sex in his nightmarish world of the future. Broadway and Hollywood began in the same decade to use the zipper to convey images of promiscuity: Rodgers and Hart's 1940 musical Pal Joey included a famous pantomime striptease with the refrain of "zip" throughout. Rita Hayworth, in her 1946 movie Gilda, used the zipper more than once as an instrument of sexual provocation. Even in the realm of urban legend, the zipper quickly became a common trope, conveying the awkwardness of relying on the mechanical in the intimate realms of daily life.

In the course of the twentieth century, the zipper became so ubiquitous as to become almost invisible. It has multiplied in form, size, style, and function; ranging from the simple plastic of the Ziploc bag to the zippers used in surgery and spacesuits. Arguably the most characteristic fastener of the twentieth century, the zipper has still not, even in the twenty-first century, lost its symbolic power to convey sexuality, opening and closing, separating and joining. And, despite the apparent allure of alternatives from old-fashioned buttons to modern Velcro, zippers appear in no danger of being displaced as the leading fastener.

See alsoFasteners; Uniforms, Military .

bibliography

Friedel, Robert. Zipper: An Exploration in Novelty. New York: W. W. Norton, 1994.

Gray, James. Talon, Inc.: A Romance of Achievement. Meadville, Pa.: Talon Inc., 1963.

Robert Friedel

Zipper

Zippers provide easy opening and secure fastening to luggage, clothing, and even plastic bags. Although zippers are found in many everyday items today, the zipper did not immediately interest people when it was first invented.

Elias Howe (1819–1867), inventor of the sewing machine, patented the first zipper in 1851. He called it an "automatic, continuous clothing closure." Howe never marketed his invention, though. Whitcomb Judson patented his "clasp locker" in 1893. After its introduction at the World's Fair (see entry under 1900s—The Way We Lived in volume 1) in Chicago, Illinois, and the successful marking of his product through his Universal Fastener Company, he became known as the "Inventor of the Zipper."

Judson's invention laid the groundwork for modern zippers. Gideon Sundback, an employee of Universal Fastener Company, designed a zipper in 1913 that is much like the zippers found today. Sundback's "separable fastener" received a patent in 1917. The Universal Fastener Company started producing hundreds of feet of it a day.

The B. F. Goodrich Company put Sundback's fastener on its rubber boots and called the device a "zipper." The name stuck, but it took several years for the zipper to become popular. For the first twenty years of its existence, the zipper only closed boots and tobacco pouches. Other uses seemed impractical; the zipper was expensive, it rusted, and it sometimes broke open. But when designers started using zippers in children's clothing in the 1930s, it did not take long for zippers to replace buttons in the flies of men's trousers. Soon, zippers were the preferred fastener for trousers, jackets, and all sorts of other items. By the beginning of the new millennium, zippers came in thousands of different styles and hundreds of different colors.

—Sara Pendergast

For More Information

Friedel, Robert. Zipper: An Exploration in Novelty. New York: W. W. Norton, 1994.

"The History of the Zipper." About.com.http://inventors.about.com/library/weekly/aa082497.htm (accessed January 15, 2002).

"The History of the Zipper." Apparel Search.http://www.apparelsearch.com/zipper_history.htm (accessed January 15, 2002).

zip·per / ˈzipər/ • n. 1. a device consisting of two flexible strips with metal or plastic interlocking projections closed or opened by pulling a slide along them, used to fasten garments, bags, and other items.2. a display of news or advertisements that scrolls across an illuminated screen fixed to the upper part of a building.• v. [tr.] fasten or provide (something) with a zipper: he wore a running suit zippered up tight.