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Physics
Clouds
Cakes

Why does baking cakes in high altitude places requires additional flour and water?

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December 20, 2007 1:15AM

For a complete answer, see:

http://www.highaltitudebaking.com/science.htm

or order the book:

Pie in the Sky, by Susan Purdy The short answer is that at high altitudes: (1) Water evaporates more quickly because water boils (ie turns into steam) at a lower temperature, and (2) Anything involving air, like leavening (rising), behaves differently at altitude because there is less air and lower air pressure. You add extra water because... During the baking process, which means warming from room temperature to final baking temperature, more water will leave (steam off) a high-altitude cake. The extra water compensates for this. You add extra flour because... The lower air pressure will cause the cake to rise too much and too quickly, and can also cause the cake to "fall" afterward. I believe the extra flour slows the rising process. Ideally you would "take out" some of the leavening, but in a boxed mix you can't do that, so by increasing the flour you cause roughly the same effect (reduce the leavening-to-flour ratio). For lots of good data about this see:

http://www.highaltitudebaking.com/science.htm