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A Simple Explanation of How Pressure Cookers Work

The kitchen's most intimidating pot -- explained.

Pressure Cooker
Pressure Cooker

Once lauded as beacons of culinary convenience, pressure cookers fell out of favor as prepackaged foods began filling grocery store aisles, and frozen, microwavable meals became de rigueur in homes across America. In fact, many generation X'ers and millennials grew up not really knowing what a pressure cooker does -- unless they are fans of competitive cooking shows like "Top Chef." Forced to innovate under severe time crunches, the wiliest contestants often use pressure cookers to create tender braises and flavor-packed stocks that would have otherwise taken hours of slow-cooking to produce.


The conditions on such shows may be extreme, but most of us struggle with the same essential issue as the chefs on that show: We're so often short on time. Lazy Sundays are a lovely opportunity to slowly transform beef chuck into a tender pot roast, but as the week wears on, it's trickier and trickier to assemble a great meal. And here's where a pressure cooker comes in handy. These locked-lid pots are specially designed to drastically shorten the cook times of slow-poke food like grains, legumes, potatoes, tough meat cuts, soups, and stews. Once in, the food requires very little oversight, freeing you up to pay a few bills or chat with your kids until dinnertime. In fact, we believe that no culinary instrument rivals these pots when it comes to creating truly delicious, healthy food so quickly. In some cases, pressure cookers can condense the cook time from several hours to 45 to 60 minutes.

Inside a Pressure Cooker

How do these crazy-cool contraptions work?

A pressure cooker is a metal pot with a special lid outfitted with a pressure regulator or gauge and pressure-relief valves. The lid locks into place on the pot, creating an air- and steam-tight seal.

Now, when you have a container of water, at any temperature, some of that water will vaporize into the space above it. In an open container, the water will keep vaporizing into steam until, eventually, it's all evaporated away. In a closed pot, however, there is an equilibrium between water vaporizing into steam and steam condensing back into water. At temperatures lower than the boiling point, this vaporization happens only near the surface. Microscopic bubbles of steam form in the liquid but are immediately crushed by the atmospheric pressure. In the sealed container of a pressure cooker, the water reaches a higher temperature where the bubbles can overcome the higher pressure. These bubbles provide enough additional pressure to increase the temperature beyond boiling -- helping cook the food. The pressure also forces moisture into the food, thus helping it cook quicker. That's at least the quick explanation.


Want a more detailed explanation? Check out our video below for more history and science.

Pressure Cooker Carnitas
Carnitas cooked in a pressure cooker.

Pressure cookers vary from model to model, so please do take the time to read through your user manual and make sure you are working in a way that’s safe and smart. Always inspect your pressure cooker before you cook, confirming that it’s completely clean, that the gasket fits snugly in place and is not damaged, and that all rubber and silicone parts are intact. Tighten any screws that have loosened. Your manual should also tell you how much water you need, and how much you can fill the cooker (generally, the pot should be no more than two-thirds full and, for some recipes, just 50 percent full).


Never, ever (ever!) open a pressure cooker that has not been depressurized. There are three ways this happens: Wait for the pressure to be released naturally, which usually happens about 10 to 20 minutes after you remove the pot from the heat; carefully transport your apparatus to an ice bath or a sink with running cold water -- for reasons that should be obvious, this is not an appropriate option for an electric cooker; or you can use the quick-release option found on most modern cookers. This function enables you to quickly release pressure by turning a knob or pushing a button. Again, every machine is a little different, so consult your user manual to know when and how to use each method. From there, you'll be ready to explore all that your pressure cooker can do!


Okay, ready to get cooking? Martha has some amazing recipes for your pressure cooker, like this light, bright pressure-cooker risotto with shrimp, or this rich, tasty coq au vin. Have fun!

About the Author

ChefSteps Team

ChefSteps is a Seattle-based food and technology company on a mission to help people cook smarter. and its companion app are designed to inspire creativity and encourage experimentation in the kitchen through high-quality interactive content, techniques, tools, and resources. The team behind ChefSteps is made up of many voices -- chefs, scientists, photographers, writers...


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