A toaster is a small appliance that uses heat to brown and harden bread.
The practice of browning bread is an ancient one. Early civilizations placed bread over an open fire in order to keep the bread from growing mold. The Romans brought the idea back from Egypt in 500 B.C. and then took it to Great Britain when they invaded in A.D. 44.
In the eighteenth century, a hinged fork was used to hold the bread and prevent it from falling into the fire. With the appearance of wood and coal stoves in the 1880s, a new toasting method was needed. This led to a tin and wire pyramid-shaped device. The bread was placed inside and the device was heated on the stove.
Fire was the source of heat for toasting bread until 1905 when Albert Marsh, an engineer, created an alloy of nickel and chromium, called Nichrome. Marsh's invention was easily shaped into wires or strips and was low in electrical conductivity. Within months, other inventors were using Nichrome to produce electric toasters.
In 1905, Westinghouse introduced a toaster stove that featured a heating element on a raised base. The bread was placed in a wire mesh tray that lay across the heating element. Five years later, General Electric received the first patent for an electric toaster. This first model was a bare wire skeleton with a rack for the bread. A single exposed heating element (nickel wire woven through sheets of mica) toasted the bread. Temperature could not be controlled, and the bread had to be turned manually.
At first, the electric toaster was primarily used in restaurants because the majority of homes had limited access to electrical power. In most cases, electricity was not available during the daylight hours. However, as public demand for labor-saving appliances in the home increased, electric companies began to offer 24-hour service.
In the early twentieth century, a flip-top toaster appeared. It had a side panel that lowered for insertion and turning of the bread slices. The Estate Stove Company developed a square box that could toast four slices at the same time. Still, these early toasters did not have any type of sensor, so the bread had to be constantly monitored. During World War I, an employee in a Minnesota manufacturing company named Charles Strite began developing a toaster that would work automatically. Strite first built an adjustable time and attached it to a spring. The timer turned off the heating element and released the spring, causing the toast to pop up.
Strite patented his toaster in 1919 and began selling it to restaurants under the brand name Toastmaster. Because each toaster was made by hand, production was extremely slow. In 1925, Murray Ireland joined the company and redesigned Strite's original plans so that the toasters could be mass-produced.
The first toaster with a piece of bimetal in the timer circuit appeared in the late 1920s. In 1930, the Proctor Electric Company produced an automatic toaster with a timing strip. By the end of the 1940s, the Sunbeam Corporation had improved the bimetal sensor control so that it was triggered by the heat from the bread instead of the heating element. When the bread reached 310°F (154°C) the sensor automatically turned off the heating element. In 1955, General Electric created its Toast-R-Oven.
In the late 1950s, two men in the United States invented the microchip. Jack Kilby and Robert Noyce, working independently, discovered that they could create an integrated circuit on a thin layer of silicon. The microchip transformed many industries. For toaster manufacturers it meant a sophisticated means for gauging the moisture in the bread and determining the precise heating time for different types of breads.
In the late 1970s, the development of heat-resistant plastics offered more options for toaster design. Models with rounded sides in a variety of colors became popular. Wider slots for bagels and thick slices of bread also appeared, as well as models with up to six slots for multiple toasting.
By the twenty-first century, the term smart toasters was a frequent marketing term. Using microchip technology, these toasters are programmed to toast a variety of baked goods from bagels to English muffins to frozen pastries. Dual versions were also introduced. Hamilton Beach introduced a combination toaster/oven/broiler that can toast bread and bake coffee cake. Black & Decker's Versa-Toast 4-Slice model allows consumers to toast two separate types of bread, such as an English muffin and a slice of raisin bread, at the same time.
Toasters and toaster ovens are constructed from a long list of intricate parts that includes a heating element, spring, bread rack, heat sensor, trip plate, level, timing mechanism, electromagnet, catch, and browning control. The various parts are constructed on site from a variety of metals and molded plastics. Screws, nuts, bolts, and washers are used to join the parts together.
To make heat-resistant plastic cases, flame retardants and smoke suppressants are added to the petroleum and coal compounds of plastic. If the toaster case is to be metal, aluminum is generally used. Mica is also used because this fire proof, flat sheet made of aluminosilicate minerals holds the nichrome wire.
Design is an integral step in the manufacture of toasters. Toasters are made with a variety of features and are in a constant state of redesign. Design innovations of the last two decades include wider slots for larger slices of bread and bagels, heat resistant plastics for toaster bodies, and microchip controls. The construction process is a complex one; therefore, detailed designs are needed to insure the proper assembly of the toaster's countless parts. The manufacturer's design staff creates prototypes of updated innovations. The prototypes are then subjected to a battery of tests. Some of the prototypes may be test-marketed for consumer approval.
The type of toaster dictates the number and types of parts. Manual toasters, those with turnable toast racks, are of the simplest construction. Semi-automatic toasters incorporate some type of signal features, such as a buzzer, to announce the end of the toasting cycle. These toasters may also have a thermostat that is controlled by the surface temperature of the bread and a regulation dial to adjust the level of brownness. Semi-automatic toasters do not have a pop-up feature.
Automatic toasters use an electrical current to brown the bread. The pop-up feature appears in all automatic toasters in which the heating element is connected to a thermostatic switch or timing device.
Making the case
1 Today, toaster cases are generally made out of pressure molded
plastic. Plastic pellets are fed into a hopper and heated to 350°F
(177°C). As the compound heats, it becomes semi-fluid. It is then
poured into a toaster case mold and cooled. After the plastic cools and
hardens, it is removed from the mold. If the toaster case is aluminum, a
sheet of aluminum is placed on a conveyor belt and taken to a punch
press. The punch press has a die that quickly exerts pressure
- 2 The punched aluminum sheet is then conveyed to a backward extrusion press. The sheet is placed inside of a toaster-shaped die and the press forces a punch against the sheet. The metal flows backwards around the punch forming a hollow, toaster-shaped shell.
- 3 Batches of Nichrome wire are shipped from a manufacture to the toaster factory. These wires are loaded into a machine that automatically wraps the wire around a mica sheet.
- 4 The mica sheets wrapped with Nichrome are then placed back on the assembly line and two are bolted to the toaster base.
- 5 In between the mica sheets is the spring-loaded tray. This tray is manually set and screwed into place.
- 6 A single bi-metallic element is connected to a support bracket, which is then mounted onto a second bracket that allows for a pivoting motion. A spring is installed between the two brackets. A stop is mounted on a mounting bracket to lock the support bracket when it is activated by the toaster carriage assembly. A release assembly is attached to the bimetallic element.
Assembling the terminal board
- 7 Two rectangular sheet-metal conductors are layered above and below a sheet of insulation. The terminal board is then screwed or welded to the toast rack. The terminal ends of the temperature-sensing device are attached to the ends of the conductors by screws.
Installing the base
- 8 The electrical cord is threaded into the molded plastic base. The various toaster parts such as the wire brackets and terminal board are attached to the base. The toaster body is then fitted over the base.
Very few byproducts result from the manufacture of toasters. However, there is frequently excess waste from the plastic molding or metal stamping processes. Plastic waste is collected and reprocessed for use in other plastic products. Scrap metal such as aluminum can be recycled into a new metal form as well for reuse.
Toasters are regularly tested on the assembly line. They are tested for durability and functionality. Companies typically generate toasting reports consisting of how well the bread was toasted, at what temperature the heating element turned off, and how quickly the bread toasted. This can result in large amounts of toasted bread. One company donates the toast to ranchers who use it as livestock feed.
The toaster continues to be modified according to new technology. Designers create new, versatile looks that fit into any kitchen. Size and capabilities range from simplistic to extreme. In 1996, two University of Washington engineering students designed and created a talking toaster. This toaster allows the user to specify verbally what setting they would like (light, medium, or dark) and the toaster verifies this aloud. Although the design specifications are available, there is no sign of its mass production.
The toaster itself has become an icon. Toasters can be found on clothing and on CD covers, as salt-and-pepper shakers, and as artwork. The most outrageous example of the latter is a mosaic made with 3,053 pieces of toast for an Italian art gallery.
Where to Learn More
Alphin, Elaine Marie. Toasters. Minneapolis: Caroirhoda Books, 1998.
Travers, Bridget, ed. World of Invention: History's Most Significant Inventions and the People Behind Them. Detroit: Gale Research Inc., 1996.
Anderson, Corin. The Talking Toaster Home Page. 8 September 1996. December 2001. < http://www.the4cs.com/~corin/cse477/toaster/ >.
Huggler; Peter E. "Temperature Sensitive Timing Assembly for Toaster Appliance." United States Patent and Trademark Office Web Page. Patent no. 59,01,639. 19 December 1996. December 2001. < http://www.uspto.gov/patft/index.html >.
The Toaster Museum Foundation Web Page. September 2001. < http://www.toaster.org/museumintro.html >.