Kettles first appeared in China. Made from iron and placed on an open fires. Over time, as areas for cooking and kitchens started to appear so the kettle began to evolve a flat bottom so they could sit on modern stoves.
All kettles are designed to boil water and for the water to used immediately. Kettles aren’t design to keep the water at that high temperature once switched off. Slowly the water inside loses heat ans cools when the kettle taken away from its source of heat.
Although we now have electric kettles, introduced in the early 20th century, the design elements haven’t changed very much. Each kettle has a handle, a spout and a lid at the top for filling it with water.
Newer models are made from stainless steel and also from plastic materials, special engineering grade plastics able to withstand the high temperatures.
Electric kettles use a heating element, enclosed in a metal sheath. The higher the power rating the quicker the water boils. Because all of the heat produced by the element is inside the kettle, they tend to be more efficient than stove based kettles where some of the heat by the stove is lost and ends up heating the cast iron gas rings and surrounding air.
When the Kettle Boils
Stove kettles often come with a whistle, which is activated by the steam from the boiling water. This starts at quite a low volume and increases as the water boils more rapidly and produces more steam.
The whistle alerts you to the fact that the water has reached boiling point but doesn’t switch the kettle off. So if left alone all the water will boil away. A kettle with no water will be damaged be the continuous heat still being applied.
Electric kettles fixed that problem as they have a mechanism to switch off the kettle once the water has boiled. A bimetallic strip is used to flip a rocker switch so the power is cut to the heating element.