Even during a Bad Hair Week, I don't have to worry about unruly curls. That wasn't always the case. When I was in elementary school, my mother gave me a home permanent. Memories of the resulting Little Orphan Annie frizz have kept me away from permanents permanently. I have straight hair and that's fine with me.

The natural curl of your hair depends on the shape of your hair shafts. My hair is straight because my hair shafts are round. If a hair shaft is oval, the hair is wavy. If a hair shaft is flat, the hair is curly. That's the natural way of things. As my mother learned (to my detriment), you can mess with Mother Nature.

When you curl your hair–whether it's with water and styling gel or a permanent wave kit–you are messing with the chemical bonds that keep the protein fibers of your hair stuck together. (Hang on--we're going to venture into a little chemistry here. But don't be scared. It's nothing a Bad Grrl can't handle.)

The chemical bonds that hold your hair together include hydrogen bonds--a weak attachment that comes about when a hydrogen atom dangling off one protein is attracted to the oxygen atom dangling off another protein.

Water is made of hydrogen and oxygen--it’s called H2O because every molecule of water has two hydrogen atoms (H2) and an oxygen atom (O). When you wet your hair, water molecules sneak in between the proteins of the cortex and join these hydrogen bonds. Your hair swells up, absorbing up to 30% of its weight in water.

In wet hair, one protein molecule doesn't have a hydrogen bond directly to another protein molecule. Instead, a protein is stuck to a water molecule, which is sticking to another water molecule, which is sticking to another protein. That's much weaker than having one protein stuck directly to the other protein--which is why wet hair is much weaker and more likely to break than dry hair.

That's also why you can curl your hair when it's wet. If you set your wet hair in curlers or pull your curly hair straight, then let it dry in this new shape, the hydrogen bonds will reform in a new position. Of course, when your hair gets wet again, those hydrogen bonds will weaken and then reform in their original position, giving you back the hair you didn't want--making curly hair straight, straight hair curly.

If you want a permanent change, you can perm your hair. In a perm, you don't just break the hydrogen bonds that hold the proteins together. You add chemicals that break the disulfide bonds (bonds between sulfur atoms). Then you reshape your hair and add chemicals that reconstruct those disulfide bonds, holding your hair in a new shape. Since these disulfide bonds withstand water, your new hairdo will be waterproof.

Unfortunately, about ten percent of the disulfide bonds that break when you are perming your hair don't reform again. So the proteins in permed hair are held together more weakly, and the hair is more likely to break and get split ends. That's the price you pay for messing with Mother Nature.