Did you know? How Shirt buttons are made?
Raw Materials
The common material for buttons is polyester, which is a special kind of plastic with properties that make it suitable for buttons. A variety of chemical dyes are added to the polyester to make different colors. To make buttons with the pearlescent sheen of shell buttons, red carbonate is added to the polyester. Black buttons are made with the addition of carbon black, and white buttons are made with titanium. The button making process also requires a chemical catalyst that hardens the polyester, and wax.
Mixing the polyester
1. Polyester arrives at a button factory in liquid form. At the start of the manufacturing process, polyester is drained from its storage tank and measured into a stainless steel kettle. Then dye is added, if the buttons are to be any color other than the natural translucence of the polyester. After the dye is mixed in, the liquid polyester is poured into a 3-gallon (11 l) metal beaker. The catalyst and liquid wax are added.
Pouring into the cylinder
2. The mixture of polyester, catalyst, and wax is then poured into a large rotating metal cylinder. The cylinders are made of steel and lined with chrome, and are typically 2 feet (61 cm) long and 4 feet (122 cm) in diameter. The cylinders lie on their sides on rollers which rotate the drums at 250 rpm. The polyester solution is slowly poured into the rotating interior of the cylinder, and the centrifugal force of the rotation causes the solution to spread, lining the drum with an even sheet. A greater amount of polyester is used for thicker buttons, and less for thinner ones. A 2-inch (5 cm) lip around the ends of the cylinder prevents the polyester from leaking out.
Hardening the sheet
3. As the polyester rotates in the cylinder, it begins to interact with the chemical catalyst and harden. The wax rises to the top of the sheet, and also sinks to the bottom, so that the hardening polyester is eventually held between two layers of wax. This process is completed after 20 minutes of rotation. The resulting polyester sheet has changed from its liquid state to a crumbly solid likened to the consistency of stale cheese.
Cutting the sheet
4. When the sheet has reached the proper hardness, the drum is stopped and the sheet is cut. Then it is rolled out of the cylinder onto a wooden tube. The wax makes it easy to remove from the drum, but the material is still very delicate. The top layer of wax is then peeled off, and the sheet is transferred to a blanking machine.
Cutting the blanks
5. The blanking machine moves the polyester sheet along on a conveyor belt. As the sheet passes along the belt, circular steel cutting dies descend and punch out button-sized circles, called blanks. Buttons come in standard sizes, and different diameter dies can be loaded into the blanking machine, depending on the size needed. After the blanks are cut, they fall into a chute, and the punched out sheet of polyester rolls beneath the chute. Cutting the blanks from the sheet takes from two to four minutes, depending on the size of the buttons being made.
Cooling the blanks
6. The blanks at this stage are hot, because the polyester is still reacting with the catalyst, releasing heat. So at this point the blanks are removed from the chute and poured into a nylon bag. The bag is then lowered into a tank of salt water, which is heated to 230°F (110°C). The blanks float in the salt water for 15 minutes. The water slowly cools, and the polyester blanks harden. Next, the nylon bag is transferred to a cold water tank, and the blanks reach their final state of hardness. After the hot and cold baths, the blanks are dried in a centrifugal drying machine, which spins them in a wire mesh basket.
Styling the blanks
7. The blanks are now ready to be cut into their finished button shape. The exact design of the button can be specified by a clothing manufacturer, and the button maker must make a steel cutting tool according to the design he is given. A different cutting tool is needed, for example, to make a beveled edge or a flat one, or to make a slightly concave button. When the appropriate cutting tool is in place, the buttons are poured into a hopper at the top of the cutting machine. The blanks fall into a holder where they are clamped tightly and moved toward the cutting tool. The spinning blade advances and cuts the button, then retracts. Next, the button moves beneath a set of drills, which create the holes. Like the cutting tool, the drills must be designed to conform to the clothing manufacturer's specifications. The design specifies not only two holes or four holes, but the diameter of the holes and the distance between them as well. After the buttons pass beneath the drill, they are sucked by vacuum out of the holder and into a box beneath the machine. Hundreds of buttons a minute can be made this way, though the number varies according to the size of the button and the complexity of the design.
Finishing the buttons
8. After the buttons are cut and drilled, they have rough or sharp edges, scratches, and tool marks. They are placed into hexagonal tumbling drums, which contain water, an abrasive material, and a foaming agent. The drums spin for up to 24 hours. The buttons bounce around in the drum until they are smooth and shiny. After tumbling, the buttons are washed and dried.
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