Perm lotions usually use ammonium thioglycolate or ATG (a reducing agent); the basic theory of  creating a permanent curl is you bend the hair fibre over a circular shape with tensions, add the chemical that will soften the hair by breaking some of the disulphide bonds allowing the hair to take shape as required and then you ‘harden’ the hair (using an oxidising agent usually hydrogen peroxide) to set the hair.  These products may be called a neutraliser.

This last step is sometimes called ‘reforming’ the bonds. but this cannot occur exactly as the hair was before in its natural state; once the disulphide bonds have been broken, the same bonds are not all reformed.  Break too many of these bonds, and the hair may break as well. This process is not perfect and not all disulphide bonds will be reformed.  Permed hair is also under stress and can start to revert to its original conformation over time.  Additionally, damage may be done to the hair by the hydrogen peroxide in the neutraliser which although used at much lower concentration than in bleaches (see above) can still cause some oxidative damage to the hair.

Perming the hair usually follows the following basic steps:

  • Stretch the hair into the shape you want with tension; this could be over a rod or barrel if you wish to a curl or combing the hair straight when the product is applied to create a straight tension.
  • Apply a chemical (e.g., ATG) to break the disulphide bonds in the hair to soften the hair enough to keep the tension shape.
  • Apply another product (a neutraliser usually based on hydrogen peroxide) to stop the softening and reform some of the disulphide bonds so keeping the hair in its new shape.

The hair is usually washed, sectioned, rods applied to the hair, and then the perm lotion is applied.

Enough tension must be applied to the hair as it is wound around the rods to provide the stress required to encourage bond-breaking; if too much tension is used, that hair can be stretched beyond its elastic range, transforming it into a brittle substance that will easily fracture the waving lotion is applied.

Many problems arise from an inappropriate application, e.g., the rods are too small, the hair is too long (should not be longer than 15cm for most rods), there was too much tension on the hair.

The application of the perm lotion usually is between 5 to 20 minutes, depending on the condition of the hair and the manufacturing instructions of the perm lotion.

The time stated by the manufacturer for safety varies, but application time and processing time should be factored into the process together. The product starts processing once the product is in contact with the hair.

Due to the way perms are applied, it is almost impossible not to perm pre-processed hair; it is imperative a test cutting is taken before the perm is used to ensure the hair is strong enough to withstand the chemical procedure. Breakage usually occurs at the junction of the new growth, and previously treated hair meet.

Careful application to new growth only and previous conditioning of the hair can help prevent excessive breakage.

There are different types of perm lotion as not all hair perms the same; Normal, resistant, and Coloured/sensitive. Thick/coarse hair and undyed hair may require longer to process them than permanently dyed or bleached hair. A test curl should be performed to determine if the desired amount of curl has occurred.

Once the hair has been checked and the perm noted to have created the correct curl, the hair should be neutralised. This is where the curl is fixed and the hair ‘hardened’, this is usually through applying a hydrogen peroxide /aqueous mix to saturate the hair whilst the rods are still in place.

This sets for 5 minutes and then the rods are removed.

Some hairdressers may not dry the hair after this allowing the hair to curl naturally and ‘air dry’ usually, the hairdresser asks the person not to wash their hair for a few days after the perm; this is to keep the curl intact by exposing the hair to water and detergents the curl may ‘drop’, and the perm not become as curly.

Washing the hair after a perm will not cause breakage unless the hair has been damaged to a severe extent by the perm lotion first.

Hair damage can occur by a perm lotion in the following circumstances:

  • The perm lotion has been over-processed.
  • The was too much tension on the rods.
  • The incorrect perm potion was used.
  • The hair type was inappropriate for a perm
    (exceptionally thick or lengthy hair is not suitable for perming).
  • Letting the hair get too hot.

National Occupational Standards have been written for perming services and can be viewed via the website:

Perm Damage
Perm Damage
Perm Damage
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Perm FAQ:

There are three main types of bonds in the hair; the strong disulphide bonds, the amide bonds and the weaker but more abundant hydrogen bond  as well as some electrostatic bonds formed and re-formed when the hair is wet, then dried.  

In many cases of over-processing with perm lotions, some of the disulphide bonds have been broken. The hydrogen bonds are the only thing keeping the hair together, so once the hair becomes wet again, hydrogen bonds naturally break and then the actual damage to the hair becomes apparent.

The person rewashes their hair, exposing the hydrogen bonds to water; they then note the significance of the hair damage.

It was not the product that caused the damage, nor the water, but these factors allowed the hair to fall into its natural state.

Using ‘the wrong’ shampoo can make your hair ‘feel’ dry but cannot cause hair damage.

Certain shampoos can help with damaged hair, they gum up cracks, smooth down cuticles and generally make it feel better. Still, shampoos and conditioners cannot ‘repair’ i.e., reform broken disulphide bonds or reverse significant hair damage caused by bleaching.

‘Repair’ is an overused word in the cosmetic industry, and it does not mean the same thing as you think.

When you hear the word repair, think ‘make better than it is and not ‘make as new/repair/reverse all physical damage’. Some repair claims may rely on the hair looking better after application of the product.

You may use cosmetic products after the hair has been damaged to make it feel better, but the damage caused by a bleaching agent is permanent to the hair fibres it has touched.

Most severe damage will either be cut out or grow out.