How Do Perms Work?

Do you love curly hair? Some people born with straight locks may wish for a little more bounce to their tresses, and those with heads of curls may struggle with styling them every day. Generally it’s good to work with your hair’s natural style, but if you’re aching to have cascading ringlets then you may want to try getting a perm, or a permanent wave. Permed hair has fallen in and out of fashion over the years, but it’s still a great way to achieve the look you want without spending hours with a curling iron each day.

At its core, a perm uses chemicals to break the bonds of each hair, and reform them into new shapes. Most of the earliest hair-curling techniques used heat; wigmakers had figured out how to permanently curl their hairpieces using caustic chemicals, but these were too harsh to be used on human hair. The earliest machine meant to permanently curl the hair was invented in 1872, by Marcel Grateau. He used a specially made pair of tongs that closely resembled a modern-day curling iron; after they were heated over a flame, the metal would be combed through the hair to create a two-dimensional wave.

Over the next several decades, other inventors contributed various developments to the perm as we know it today. This included the use of water and steam to help prevent overheating, the creation of multiple rollers to spiral locks of hair and curl them all at once, and the addition of alkaline reagents to speed up the process and make the results last longer.

The modern perm started in 1938, with Arnold Willatt’s cold wave technique. It did not use heat or machines; hair was wrapped around long rods, and a reduction lotion containing ammonium thioglycolate was applied to the roots. This lotion broke down the links between the main structural polypeptide bonds in the hair protein; these links, which are called disulfide bonds, are what give hair its elasticity. Once they were broken apart, hydrogen sulfide was used to halt the reduction process; it caused the disulfide bonds to re-form, this time in the shape of the round rods, producing a head full of bouncy curls. The hair would retain its shape for long periods of time because the actual chemical composition of each strand had been altered, rather than temporarily shaped with heat. Nowadays, a perm uses sodium thioglycolate instead of ammonium, reducing the time required to break the chemical bonds in the strands and increasing the pH level; it’s easier on the hair than ammonia. Some at-home perm kits use very low pH formulas, and add heat to facilitate the chemical process. A digital perm uses a digital display to program the desired shape and texture of each wave, and is very popular in Korea and Japan.

Perms are generally safe for most people, but the chemicals can still cause skin irritation and it’s important to minimize contact as much as possible. There’s also a very fine line between unlinking and reforming the disulfide bonds and breaking them completely; if this happens, then the hair will become brittle and fragile. It’s best to get a perm with a professional who is comfortable with the technique, especially if you’re new to the style.