Hair Relaxers: Breaking Nature's Bonds

Thanks to hair relaxers, you can walk into a salon curly and leave straight. Zoom in on the chemistry of your curls with Groupon’s introduction.

Human hair is flexible enough to run wild as a mountain stream one day and fall as straight as water over the Hoover Dam the next. But to make lasting changes to its texture, you need to go beyond the reach of styling tools down to the chemical level. All hair is made of keratin, a hard protein that’s also central to our skin, nails, and exoskeletons. To form a single hair, keratin molecules link together in different patterns with the help of three types of chemical bonds: hydrogen bonds and salt bonds, both of which break easily in water and reform when dry, and disulphide bonds, which can only be broken by certain chemicals. In straight hair, the disulphide bonds are evenly aligned. In curly hair, however, the bonds occur irregularly and at odd angles, causing the hair to twist and kink on its way down.

When you style your hair with heat or water alone, you break the weaker hydrogen and salt bonds to allow your do to take a new shape. Once water touches your hair, however, the bonds reform in their customary way, and you’re back where you started. Chemical relaxers, therefore, work by dissolving the hair's tough, waterproof disulphide bonds and preventing them from reforming in their normal pattern.

The most powerful hair relaxers contain sodium hydroxide, otherwise known as lye. Given lye’s presence in drain openers and oven cleaners, you might guess that it can be quite harsh on human skin, which is why no-lye relaxers made from guanidine hydroxide are also common. There is a trade-off, however: some find that lye relaxers are harder on the scalp but gentler on hair, and work more quickly so that you can get back to staring at your hair in the mirror sooner. An experienced stylist can recommend the best method for your hair.