Evolution of Zippers:
Zipper is the brain child of Mr. Whitcomb Judson. It was introduced in 1893 at the Chicago World’s Fairthen with the name ‘Clasp Locker’. Gideon Sundback, an electrical engineer, who was hired to work for the Company designed the modern zipper in 1913. This zip had ten or eleven fastening elements (old one had only four) for an inch, two facing tows of teeth that can be pulled into one piece by the slider and increased opening for the teeth. The infamous zip came into existence, when B. F. Goodrich Company, wanted to use it for their new product boots. They renamed it as zipper which is in practice till today. It took twenty long years for the fashion industry to get convinced and accept zippers as a part of the garment.
Initially, during 1930s zippers were featured in childrens clothing complementing them for helping children to dress up quickly and by themselves. Zippers came into limelight in 1937 through the French fashion designers who used them on mens trousers. Esquire magazine described the zippers as “Newest Tailoring Idea for Men” The next big boost for zippers came when they were used on jackets and could be opened on both ends.
Types of Zippers:
Coil Zippers: This is the most commonly used zipper. They run on two coils on either side. There are two types of coils. One is the spiral coil, with a cord running inside the coil. The second one is in the ladder form called Ruhrmann type and is used mainly in South Asia.
Invisible Zippers: They have their teeth behind the tape whose color matches exactly with the dress color and the slider and so gives an invisible appearance. They are usually coil zippers and are used mainly in skirts and other dresses.
Metallic Zippers: These types of zippers are mainly found in jeans today. They are made of stainless steel, aluminum, brass, zinc, or nickel alloy. Pieces of metal are molded into teeth and are set in a tape at regular intervals. They can be painted in any color to match with the dress.
Plastic molded Zippers: They are similar to metal zippers except the fact that they are made of plastic. They can be easily made in any color of plastic to go with the product. Polyethylene resins and mainly polyacetal resins are used to make plastic zippers.
Open-ended zippers: They are used mostly in jackets and have a box and pin” mechanism to lock the two sides of the zipper into place. They can be any of the above specified types
Closed-ended zippers: This type is used mostly in baggage and is closed at both ends.
The key elements required for making a zipper is a stringer which consists of a tape and teeth assembly, a slider to open and close the zipper, and a tab to pull the slider. A separating zipper has a box and a pin instead of a bottom stop. The tapes are made either of cotton or polyester or a blend of both.
Making of the Metal Zippers:
The stringer is made by passing a wire through a rolling mill to form a Y shaped wire. This is then cut to make the tooth for the zipper. The tooth is then punched into a scoop with a die and is put in a slot on a rotating turntable. The turntable is rotated to 90 degrees and another tooth is fed into the slot. This tooth is clamped into a cloth tape. In a second method, the wire is passed through a head and pocket punch, to make scoops. A blanking punch cuts the scoops and makes the Y shape. The legs of the scoop are then clamped to a cloth tape. This method proved faster than the previous Sundbacks method. Yet another method is prevalent wherein a chain of teeth in molded and clamped around a cloth. This cloth is injected with molten zinc under pressure. The mold is cooled by the water and shapes the teeth. Residues are finally trimmed.
Making of the Plastic Zippers:
Stringers for plastic zippers are made similar to metal ones. Two methods are prevalent to make plastic zippers. In the first method, a round plastic wire is fed in between two heated screws. One screw rotates clockwise, and the other one counter-clockwise. This rotation forms loops in the wire. A head maker presses the loops into a round knob. It is then cooled. Left and right spirals are made simultaneously from two different machines, so that they match with each other. Under the second method both left and right spirals are made from the same machine. A piece of wire is looped twice between notches on a rotating forming wheel. A pusher and head maker works at the same time to form the notch and the head at a time. This process makes a zipper that is already linked together in a cloth tape. Superior quality of plastic zippers is
Made by weaving them directly into the cloth like weaving.
A zipper should meet the textile quality standards. Once manufactured, the zipper is tested for its flatness by passing a gauge set at a certain height. If the gauge touches the zip many times, it means the zipper is defective. It is then tested for its straightness by laying it across a straight edge and is scrutinized for any curving. Zippers are tested with small steel balls to test coating for abrasion. They are also tested for shrinkage. Two marks are made in the tape, and they are measured before and after washing or heating, to check if there is any shrinkage in its length. Normally light weight zippers will have one to four percent shrinkage and heavy weight zippers will not have any.