How a Sealed Pot Changes Cooking
Water at normal atmospheric pressure boils at 100 degrees Celsius (212 degrees Fahrenheit), and no matter how hard it boils, it does not get hotter. If the pot is sealed so that steam cannot escape, pressure builds up and the boiling point rises. At the pressures used by typical household cookers, the contents reach temperatures somewhat above 110 degrees Celsius, often in the neighborhood of 115 to 120. Food therefore cooks faster, which is why tough cuts of meat, dried beans and stocks can be ready in a fraction of the time. Because the lid keeps steam in, less liquid is needed too.
Denis Papin’s Digester
The pressure cooker’s usual ancestor is the steam digester of Denis Papin, a French physicist and inventor who worked in England for part of his career. In 1679 he presented his device to the Royal Society, and later published a description of it. It was a strong, tightly sealed vessel with a weighted safety valve, intended to extract nourishment from bones and soften tough food using high-temperature steam. Papin hoped that it could make cheap cuts of meat and bones more useful as food, and reportedly cooked a meal for members of the Royal Society with it.
The safety valve was important. Early pressure vessels could burst, and Papin’s design allowed steam to escape if pressure became too high. Papin also experimented with using steam pressure to push a piston, and he is among the figures sometimes mentioned in the prehistory of steam engines, though others went on to build practical engines.
From Laboratory Curiosity to Kitchen
For more than two centuries, the digester stayed mostly a curiosity or a specialist tool. Cast iron and thick metal vessels were heavy, difficult to seal reliably, and risky. Cooks used other ways of speeding up cooking, from covered pots to the cast iron range with its steady heat.
In the twentieth century, better metal casting and rubber or synthetic gaskets made practical household models possible. A Spanish inventor, José Alix Martínez, is often credited with a pressure cooker design in the 1910s, and companies in the United States and Europe marketed home cookers in the 1920s and 1930s. Aluminum made lighter pots practical, helped by advances in aluminum smelting that lowered the metal’s price. A well-publicized US model was shown at the 1939 New York World’s Fair.
War, Canning and Kitchen Safety
The Second World War encouraged home food production, and pressure canners, which are larger pressure vessels used for sealing low-acid foods in jars, became popular with households growing vegetables. Pressure canners and ordinary pressure cookers are related but are not the same thing, and tested guidance should be used with each.
Early cookers had a reputation for danger, with stories of lids blowing off and soup on ceilings. Many accidents involved blocked vents or poor maintenance. Later designs added several redundant safeguards, such as locking lids, spring-loaded valves and overpressure plugs. Modern cookers are generally considered safe when used and maintained as the manufacturer intends, but this article is a history and not a safety manual.
Steam Cooking Beyond the Pressure Cooker
Steam cooking itself is much older. Steaming food in baskets above boiling water is an ancient tradition in China and elsewhere, using bamboo steamers. Steaming gently cooks vegetables and dumplings and can preserve color and shape. Steam ovens, developed in the twentieth century, use steam injected into an oven chamber. The pressure cooker uses steam differently, to raise temperature, while an ordinary steamer works at normal pressure.
Electric and Multi-Function Models
From the mid-twentieth century, electric pressure cookers started to appear. They were slow to catch on until electronics and sensors improved, and from the 2000s and 2010s the electric multicooker, combining pressure cooking with slow cooking, rice cooking and other settings, became a popular appliance. They reflect the continuing growth of electric kitchen appliances, and compete with the microwave oven for fast cooking. Stainless steel inner pots are common in this type of cooker.
Why It Persists
Pressure cooking is a case of an old idea being rediscovered whenever fuel or time is scarce. In places where cooking fuel is expensive or heating is difficult, the cooker is valued for saving fuel. Elsewhere it is valued for speed. Papin’s belief that high-temperature steam could make cheap food go further still describes why people use it.