Up to the 1920s, if you wanted to boil water, you needed an open fire and a kettle. Vessels almost identical to modern kettles, from the shape of the body to the spout, were used in Mesopotamia as far back as 3500 B.C. Time-consuming and inefficient, it was nonetheless the only way to heat water for several millennia.
By the 19th century, kettle makers switched from iron to copper because it conducted heat more efficiently. The next significant improvement – the so-called "whistling kettle" – came along in the early 20th century and represented a major step in the evolution of the kettle. The boiling water would produce a rush of steam through an opening at the top, resulting in a loud whistling sound to notifying those within earshot. The whistling kettle was one of the more common ways of heating drinking water prior to the advent of the electric model.
The first kettle to use electricity to heat water came from Carpenter Electric Company in Chicago in 1891. However, the water took more than 10 minutes to come to a boil because of a major design problem – the heating element was in a separate compartment, rather than in the water as is the case in modern kettles.
In the 1920s, the Swan Company solved the problem by sealing the element in a metallic cylinder and placing it directly inside the water. Heating occurred much faster and before long, other manufacturers used a similar design. The kettles were usually constructed out of metal, except during World War II, when shortages necessitated a switch to ceramics.
Although he may not have been first, Arthur Leslie Large is credited with inventing the electric kettle. His adaptation of the plug-in model effectively rendered the whistling kettle obsolete as the growing electrification of the world made it easier to use the electric version.
Here's how an electric kettle works: Electricity moves through an element of high resistance, which generates heat that it transfers to the water. At the moment the temperature of the liquid reaches 100 degrees Celsius, its boiling point, the resulting steam warms a strip composed of two dissimilar kinds of metal, which curves due to the fact one of the metals expands more rapidly. The heating connection is then broken, preventing electricity from reaching the element, effectively shutting off the kettle. Such a safety feature prevents the scalding water from becoming a hazard if the person tending it becomes distracted and neglects the steaming appliance. The "cut-out" device represents a significant advantage over whistling kettles, which keep boiling, and whistling, until someone turns down the heat.
Now found in more homes than any other appliance, the kettle continues to evolve and improve. There are undersized models for people living alone and large ones to serve the needs of a family. Manufacturers are also making cordless models.