By Kim Linton

A perm, or permanent wave, is a chemical process that is used to change the structure and texture of hair. Depending on the size of the roller or perm rod used, a perm can make straight hair curly or curly hair straight. A permanent wave can be done by a trained beautician or at home with an over-the-counter perm kit.

How Does a Perm Work?

What is a Perm?

The Evaluation

Before giving a perm, the beautician will examine the condition of the hair. If the hair is overly processed or damaged, the stylist will usually suggest an intensive conditioning program or haircut to reverse some of the damage. If the client's hair is healthy, the perm can be done right away and will usually take about two hours to complete.


First, the client's hair is washed and lightly conditioned, then parted into narrow 1/4" sections. Each section is no wider than the width of the rod or roller being used, and every hair is rolled to avoid damage from the perm solution. A protective ointment is usually applied around the hairline to avoid chemical burns on the skin.

Rolling the Hair

Next the tip of each section is enclosed in a special tissue paper, then tightly wrapped around perm rods. The thickness of the perm rod determines the amount of curl; thicker rods produce less curl and thinner rods produce tighter curls. Very large rollers are used to straighten curls or waves.

The Perm Solution

After the entire head is wrapped, an ammonium thioglycolate solution is generously applied to each rod. The solution restructures the hair shaft by raising the cuticle layer and breaking down disulphide bonds. Depending on the texture and thickness of the hair, the perm solution is left on for 10 to 20 minutes.

The Neutralizer

Next the ammonium thioglycolate solution is rinsed from the hair with warm water and the rods are blotted with a towel. Each rod is then rinsed with a hydrogen peroxide solution or neutralizer, which sets the new shape of the hair by reinserting the disulphide bonds. After five minutes, the rollers are carefully removed, then more neutralizer is applied to the hair and left on for an additional two minutes. The hair is then rinsed in very warm water for three to five minutes.

Post-Perm Washing

The results of a perm vary depending upon hair texture, but typically the curls will be very tight immediately following a perm. A fresh perm should not be washed for 24 to 48 hours because water weakens new disulphide bonds. After the first washing, the curls will relax somewhat, and will continue to do so as the perm grows out. Most perms last about two to six months depending on hair type and condition.