How Perms Work

Hairdresser wrapping hair in perm rods — Photo: Shutterstock

From straight to curly, from curly to straight, and everywhere in between, millions of people do something each year to change the texture and wave patterns of their hair. It is big business. There are many rules to remember, and some myths that need to be dispelled. Let's talk about hair and perms.

Hair 101:

Your hair is composed of proteins. Each strand has a cortex at the center. The cortex is composed of proteins arranged in a chain down the length of the shaft. These proteins, called polypeptide chains, are held together by peptide bonds, giving the hair its strength.

Surrounding the cortex is the medulla, again composed of protein fibers and containing the pigment that gives the hair its color. Here is also where you'll find the side bonds of the hair, which maintain the wave pattern of the hair. There are three types of side bonds: salt bonds, hydrogen bonds, and disulfide bonds.

The salt and hydrogen bonds are weaker than the disulfide bonds, but there are more of them, and overall, each bond type constitutes about a third of the strength of the hair's curl. The disulfide bonds are what get changed in a permanent wave.

Finally, the cortex and medulla are encased in a protective sheath called the cuticle, which is made of tiny, overlapping scales of keratin (the same material from which fingernails and toenails are made). The cuticle protects the hair from the damaging effects of the environment.

Some people have hair with a tightly closed cuticle, and some have a cuticle whose normal state is slightly elevated. The arrangement of the cuticle of the hair determines how easily the hair absorbs moisture and how "frizzy" it appears.

Photo: Getty Images via Canva

Curling The Hair:

We change the wave pattern of the hair by curling it, usually with perm rods or rollers of some type. These changes occur because we alter the side bonds of the hair. The salt and hydrogen bonds mentioned above are easily broken through the application of water and heat, which is why simply wetting the hair, wrapping it in rollers, and allowing it to dry, or using a curling iron, allows you to add curl.

When the heat cools and the hair dries, the salt and hydrogen bonds reform on their own. The curl you get this way only lasts until the next time the hair is wet. Hot combs and flat irons work on the same principles to relax curls and straighten the hair.

Perming The Hair:

The process we call permanent waving uses chemicals to break and reform the stronger disulfide bonds of the hair. When the hair is washed and wrapped on a perm rod (the size of the rod determining the tightness of the curl), we place it in the desired physical shape. Then, by applying a waving lotion with an alkaline base (ammonium thioglycolate is most commonly used in today's perms), we raise the cuticle layer and break the disulfide bonds that hold the natural wave pattern.

After the waving lotion has had time to process, has been rinsed away, the rods have been blotted to remove excess water, and a neutralizer has been applied. The neutralizer is what actually reforms the disulfide bonds of the hair and sets the new curl pattern. It is also the most potentially damaging stage of the perming process and should always be closely monitored.

Once allowed to take effect, the neutralizer is rinsed away, the rods removed, and the hair re-rinsed for good measure, it can then be styled as desired.

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