Masaru Ibuka created the very first product for the company that would eventually become Sony in 1946, and it was nothing more than a wooden bucket lined with rudimentary aluminum electrodes designed to cook rice.

A cooker with no reliable stopping point

The prototype’s difficulty was not simply that it used crude materials. It depended on a delicate relationship among the water, the rice, and the electric current. In this design, electrodes sent current through the contents, heating them as electricity met resistance. But the amount and distribution of water changed how that current behaved—and therefore how much heat reached the rice.

Rice needs enough water and time to soften, but excess heat after the water is absorbed can scorch it. With no dependable way to sense when cooking was complete and cut the power, the prototype could not consistently stop at the right moment. A small difference in water level could mean undercooked grains or a burned mass.

The control problem behind the invention

That failure points to the real engineering challenge in an automatic rice cooker: making the appliance respond to the food, not merely deliver heat. A useful cooker must heat rice evenly, then recognize when the cooking phase has ended rather than continuing at full power. Later electric cookers addressed that control problem with temperature-sensing mechanisms that switch the heating cycle, instead of relying on a person to watch the pot and turn it off.

Ibuka’s wooden-and-aluminum device was therefore a product in the literal sense, but not a dependable household appliance. Its significance lies in the gap it exposed: supplying electricity was comparatively straightforward; controlling its effect on changing, water-filled rice was the harder task.