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The boiling point of water changes with changing altitudes, but most recipes are based on the assumption that the cook will be cooking at sea level. Cooks at higher altitudes need to make certain adjustments, and this is especially true with pressure cooking.

The Boiling Point of Water

As elevation increases, the temperature at which water boils decreases. At sea level, the boiling point of water is 212 degrees Fahrenheit. On top of Pike's Peak (14,000 feet above sea level), however, the boiling point is about 187 degrees. For every 540 feet of altitude increase, the boiling point decreases by about 1 degree.

Pressure cookers work quickly and efficiently by increasing the pressure on liquids, which increases the boiling point of water. (For a more thorough explanation of pressure cooking science, see 4 Reasons to Use a Pressure Cooker.) So cooks at elevations above sea level don't benefit as fully from pressure cooking's wonder-working, time-saving efficiency. Pressure cooking will still save time, energy and money, but here's the high-altitude rule:

For every 1,000 feet above 2,000-foot elevation, you must increase cooking time by 5 percent.

So if your pressure cooker recipe indicates that you should cook something at high pressure for 25 minutes and you live at 6,000 feet above sea level, you should actually keep cooking at high pressure for 30 minutes.

BogWisdom
1/7/2021 7:42:44 PM

You absolutely will see 10psi on the gage. However what the gauge is displaying is a difference in pressure between what is in side the cooker and what is outside of the cooker. As sea level the outside air pressure is higher than in, say, Denver nearly one mile higher. In PSI the ambient air pressure in Denver is about 12psi. This is compared to a vacuum and is due to the amount of air piled up on top of everything. In Denver, there's less air pressing down on things because it is closer to outer space (vacuum). If you wonder why it all doesn't just get sucked off the planet, thank gravity. In any case, the absolute pressure inside the cooker at sea level is 14.7psi (atmosphere) plus 10psi (gauge) for a total of 24.7psia (pounds per square inch absolute). At this pressure the boiling temperature of water is 239.4F. In Denver the pressure inside the cooker is 12psi (atmosphere) plus 10psi (gauge) for a total of 22psia. At this pressure the boiling temperature of water is 233.1F. So you have to cook it a little longer to get the same effect. Something to be careful about is that just adding some extra weight to the relief valve can be a dangerous thing. The cooker is rated for gauge pressure not absolute. Just because the net pressure inside the cooker is lower it is still holding back 10psi of pressure compared to its surroundings. If you want more pressure in the cooker, you need to go lower in the atmosphere to get some ambient pressure assistance. On the shores of the Dead Sea you get a 5% boost in air pressure 15.4psi. So here the temperature inside the cooker at 10psi gauge is going to be 240.9F.

Nickm52
6/10/2020 2:33:35 PM

Could you explain why you have to increase the cooking time???? If we have a 10psi pressure at 0 ft, and 10 psi pressure in 10,000 ft, what is the temperature difference in the pressure cooker??? There still 10 psi inside, regardless the outside altitude...

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