Boiling point: pressure and altitude
Also searched as: boiling point, pressure cooker, cooking at altitude, water boils at 90 degrees, instant pot
In short: Water only boils at 100 °C at sea level. In the mountains it boils sooner; in a pressure cooker only at about 120 °C.
Like a lid on a packed hall: if it presses down hard, nobody gets out until it gets really hot.
Simplified model
Temperature thresholds
5
- 71 °CMount Everest
- 90 °Cat around 3000 m
- 98 °CLucerne (around 435 m)
- 100 °Csea level
- 120 °Cpressure cooker
Below 71 °C none of this happens yet. From 71 °C: Mount Everest.
What happens
boils when its vapour pushes as hard as the air above it. Lower air pressure at altitude means it boils at a lower , about 1 °C less for every 300 metres. At 3000 m water boils at around 90 °C. A pressure cooker does the opposite: it holds the steam back, the pressure rises, and water gets about 120 °C hot. Higher temperature means shorter cooking time.
Why it matters
Explains why pasta and eggs take longer in a mountain hut, and why a pressure cooker cooks beans and braising meat in a fraction of the time.
Rules of thumb
- In the mountains, extend cooking times. More heat does not help: water there gets no hotter than its boiling point.
- Pressure cooker for pulses, stock and braises: about a third of the time.
- Open a pressure cooker only once the pressure has fully dropped.
Levers
1
In practice
2
Eggs
A 6-minute egg at 2000 m is softer than in the lowlands, because the water boils cooler.
Meat
Braised beef in a pressure cooker turns tender in around an hour.
Sources · 2
- Küchenfibel: Warum kocht Wasser in der Höhe langsamer?
- Harold McGee: On Food and Cooking (2004)