An old-fashioned Kamado stove (Ritto Folk History Museum)
Before the electric rice cooker was invented, rice was cooked on a kamado, a large stove built in a corner of the kitchen. To boil rice on a kamado, first a fire is started using firewood. Next, a pot containing the rice and water is placed over the fire. The taste of the rice depends on the strength of the heat used to cook it, but controlling the fire in a kamado is tricky. Cooking rice used to be quite a chore; one would have to watch over the fire from early in the morning in the smoky air. There's even a rhyme about the right heat for cooking rice. It goes: "Hajime choro choro, naka pappa, butsu butsu iu koro hi o hiite," which instructs the cook to begin at low heat, then increase the heat, and then lower the heat again when the inside of the pot begins to bubble.
Japan's first rice cooker (Toshiba Consumer Marketing Corp.)
The development of electric rice cookers began in the Taisho era (1912-1926), but it wasn't until 1955 that the first automatic rice cooker for household use went on sale in Japan. The company that made this cooker, Toshiba, spent five years developing it. After much trial and error, the company came up with a method called "double-pot indirect cooking," in which a cup of water was poured into the outer pot, and the machine automatically turned off when all of this water evaporated, signaling that the rice was ready.
With the birth of electric cookers that boiled rice all on their own, the kamado disappeared from homes, there was less housework to do, and the lives of Japanese homemakers changed tremendously. As manufacturers produced better and better electric rice cookers, these appliances quickly became a household fixture. A "kitchen revolution" had taken place.
A poster advertising rice cookers to overseas markets (Toshiba Consumer Marketing Corp.)
In 1960, the first rice cookers that could keep rice warm after it was cooked went on sale, as did some models with timers. This meant that people could eat freshly cooked rice for breakfast simply by setting the timer the previous night, and they could keep the rice hot and tasty even after it was cooked. Next, in an effort to make rice from rice cookers more delicious, makers introduced computer-controlled rice cookers, which regulated the temperature inside the cooker using a tiny computer. These were first introduced in 1979.