What's the Big Deal about Baking at High Altitude?

Travels sent an interesting question to me the other day:

I am at altitude and don't ever change the recipes in cookbooks. I noticed you mention this cookbook in other posts. Could you tell me basically what is different when baking at altitude? What you need to consider changing and why?


After growing up at sea level, baking at high altitude has been a disaster for me. Pure and simple. The cakes, muffins and cookies I've tried have turned out dry, flat and pathetic. That's why Pie in the Sky was such a revelation for me.

Before I moved to high altitude, various people told me to add a couple of extra tablespoons of flour and call it good. Um, yeah. Wish that had worked. So, what's the big deal (other than the fact that MY recipes didn't work)?

As it turns out, it wasn't really my fault; it has more to do with changes in atmosphere and humidity than poor baking skills. It's chemistry, baby.

In one of the early sections of her book, Susan G. Purdy dispells 12 myths about high altitude baking:

Myth #1 - Always substitute extra-large eggs for large or medium eggs in sea-level recipes

Myth #2 - At higher altitudes, add extra flour to all baked goods

Myth #3 - Always cut the leavening as altitude increases

Myth #4 - Cut out the baking soda at high altitudes

Myth #5 - Reduce the fat in rich cakes and cookies at high elevations

Myth #6 - Always raise the oven temperature by 25 degrees at high altitudes

Myth #7 - When using a glass baking dish, always reduce the oven temperature by 25 degrees

Myth #8 - Batter will overflow in cake pans at high altitude

Myth #9 - Cookie recipes don't need adjustment at high altitude

Myth #10 - Pie crusts don't need adjustment because they are not affected by high altitudes

Myth #11 - Pie fillings don't need adjustment because they are not affected by high altitude

Myth #12 - When using boxed mixes, you can count on their high altitude directions to work every time

Once you've read through the myths, though, there are still no hard and fast rules. Sometimes you raise the temperature; sometimes you lower it. You omit the baking soda to maintain acidity; or not. Substitute buttermilk for whole milk; sometimes.

Most resources recommend experimentation. Joy of Cooking has a special section and lays out some high altitude baking/cooking rules then sets you off on your own. Since I don't have the patience for that kind of thing, Pie in the Sky is the book for me. Purdy has already done all of the experimenting for me and her recipes work. I have nothing more to do than open the book, select a recipe and get to it. 

I wish that all of my sea-level recipes worked at altitude, but I just can't seem to pull it off. Travels, I'm jealous that you don't have to alter yours!