Perming Hair

The strong disulphide linkages in hair are formed when the hair cells harden into keratin in the hair follicle. These are the bonds that keep the hair shaft in shape. In order to change its shape, the disulphide bonds have to be broken down and re-formed into a different pattern. We saw that changes to hydrogen bonds in the setting process are only temporary. Chemical changes to the disulphide bonds are permanent.

HAIR FACTS

Skin: acid and alkaline After any hair care procedure, we need to consider how the skin is left, and in particular how acid or alkaline it is. The pH of the surface of normal skin is between 5 and 6. That is, it is slightly acid. This is often referred to as the skin's 'acid mantle', but this is more of an emotional than a strictly scientific statement. The acidity is due in part to the sebum, the natural oil produced by the skin, which is itself slightly acid. One important function of the skin is to protect the tissues lying beneath it. The skin does this by acting as a barrier, regulating liquid loss from inside and keeping excess liquid outside the body. It also protects the body from infection. The acidity of the skin surface slows down the growth of bacteria and makes it harder for them to enter the body. If the acidity of the skin is affected - if the pH rises above 5-6, say - infections are more likely. This can happen if the pH is not adjusted after chemical hairdressing processes such as perming, by very thorough rinsing and careful neutralization.

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

The history of perms

People have been trying to turn straight hair into waves and curls for thousands of years. The women of Ancient Egypt used to apply a mixture of soil and water to their hair, wrap it on crudely made wooden 'rollers' and then bake the muddy mess in the sun - the results would have been anything but permanent, however! In fact, as we have seen, temporary waving is still carried out by setting damp or wet hair into a new shape on curlers or rollers. Heat from a dryer and the use of a setting lotion give a firmer, longer-lasting style. But the changes to the hair are the same as the Egyptian ladies brought about: only the weak hydrogen bonds in the hair are affected, and the hair goes back to its original shape as soon as it is dampened.

The first truly permanent waves became available in 1920. The waving lotion was activated by heat from an electrical device. The early models did not have thermostats, and it was difficult to control their temperature. They had individual heaters for each curl, and clients found these heavy and uncomfortable. These early perms were harsh and drying, and left the hair in tight frizzy curls that were difficult to manage.

This permed and bleached long hair looks good at first glance, but the hair is dry and has no luster

Early in the 1940s the 'cold wave' was introduced. This was basically the perming process that we use today. The cold wave had many advantages: the unpleasant heat and weight of the old appliances were completely eliminated, and the hair could be waved closer to the scalp.

Modern perms

A permanent wave is a process that creates a curl in the hair shaft by altering its internal chemical structure. This curl cannot be destroyed except by further chemical treatment.

A perm is not necessarily an easy option. Certainly, perming creates a style in the existing hair. But after perming the hair continues to grow as it did before, at the rate of a centimetre or so every month. The new hair, of course, grows straight. So the perm has to be either repeated or left to grow out. Some hair can stand up to repeated perming quite well, some can't!

Dry, lifeless hair that has been repeatedly permed: the hair has also been bleached, and the darker roots are growing out in much better condition: at this stage it can no longer take a perm because virtually all the disulphide bonds have been broken

Hair with a long history of cosmetic processing, which is approaching the limit of its tolerance

Whether or not a perm will 'take' well depends on the basic nature of the hair, its past history of chemical treatments, if any, and the skill of the technician or stylist. Hair that has had a long history of perming, perhaps combined with tinting or bleaching, may have become so damaged as to be near the limit of what it will tolerate.

HAIR FACTS

pH and hair The key to the perming process lies in the fact that perming solution is alkaline. What exactly does this mean in relation to hair? When scientists talk to each other about alkaline solutions and acid solutions, they need a way of measuring alkalinity and acidity. The scale they use for their measurements is called the pH scale. The pH scale ranges from pH 1 to pH 14. All you need to remember is that acids have pH numbers less than 7. Alkalis have pH numbers greater than 7. The more acid the solution, the lower is the pH number; the more alkaline the solution, the greater the pH number. pH is measured using special indicator papers which change color when the pH changes. Hair responds to changes in pH. If a hair is placed in an alkaline solution it swells, and the scales of the cuticle lift. In a slightly acid solution, the scales lie smoothly and the hair is soft. In a strongly acid or alkaline solution, however, the keratin protein starts to break down.

The perming process

The hair is first washed and then wound on to some kind of former, such as a curler or a rod. The perm lotion is applied to the hair. Because the lotion is alkaline (pH about 9) the scales of the cuticle open slightly, allowing the lotion to flow under the cuticle and into the cortex. Here it reacts with the keratin of the cortex, breaking some of the disulphide cross-links within and between the protein chains. The hair swells and 'softens', so that it can stretch to take up the shape of the formers.

After a while the perm lotion is thoroughly rinsed away and a neutralising lotion is applied. This re-forms the broken cross-links, which makes the hair harden into its new, curlier shape. This stage is the key to a successful perm: failure to rinse and neutralise properly can lead to many problems, including scalp irritation and damage to the structure of the hair shaft.

HAIR FACTS

What happens during perming Today's 'cold' permanent wave lotions contain substances called reducing agents, in an alkaline solution. The reducing agent most often used is called ammonium thioglycollate. Reducing agents act on the keratin in the hair, breaking the disulphide linkages that join the pairs of cysteine units together. The result is that the keratin softens and swells. The softened hair is then put into its new shape. As it is manipulated the cysteine linkages slip past each other and realign themselves with new cysteine partners see (Coloring Hair). Neutralizing lotion is then applied. This contains oxidising agents. One that is often used is hydrogen peroxide, the same substance that is used in hair bleaches. Oxidising agents work in the opposite way to reducing agents. They make the cysteine units link together into pairs again, hardening the hair and giving it its new, permanent shape. In hair that has been repeatedly permed the original disulphide cross-links may have been broken and re-formed so many times that hardly any remain.

In order to illustrate the process of permanent waving, we will follow a client through the full procedure.

This client, like many others, wants her hair put into a manageable style, with curl and body. It is vital that the stylist understands the past history of her hair. It is permed every three or four months, and tinted more frequently. Fortunately her hair is naturally very resilient, and has not suffered unduly. In expert hands, a perm should be straightforward.

A successful perm, and a delighted client

Above, the normal internal chemical structure of the hair protein, showing unbroken disulphide bonds; in perming, bonds in the hair wrapped around a roller are broken by a reducing agent; after oxidation the bonds are re­aligned in a different order, permanently changing the shape and producing a curl

Many people decide on a perm as they get older and their hair length and density diminishes: perming gives volume and -as seen on the right - is not necessarily excessive or obviously damaging

Some people's hair is resistant to the chemicals used to open and close the scales of the cuticle. Often this is an inherited tendency. The only way to deal with it is to use stronger chemicals. Great care is needed with these, however, as they may damage the hair shaft so severely that it breaks. 

Red hair is an example of this. The keratin of red hair tends to contain more sulphur than usual - it can be twice as much as the average -because it contains a high proportion of cysteine units. That means that there are many more disulphide linkages to be broken, and it is therefore more likely that a perm will fail to 'take' on red hair.

Perm shock

Once the perming solution has been put on, the hair is in a very vulnerable condition. The keratin is softened and greatly swollen, particularly during rinsing, the cortex is in the process of being chemically changed, and the cuticle may have been slightly damaged. At this point every possible care is needed to protect the hair from any unwanted change in conditions.

For example, sudden temperature changes can damage the softened keratin to such an extent that the hair may break down completely. A story is told about a Swedish lady who was having a perm one winter's day. The temperature outside was well below freezing, although in the warm salon it was around 22 °C. The perming solution had already been applied when suddenly the lady glimpsed in the mirror a friend of hers walking by in the street. Impulsively, she rushed outside to greet her. The horrified hairdresser had to chase after her and bring her back indoors, where she set to work to try to re-equilibrate her client's head by wrapping hot towels around it to get the temperature back up again.

After perming

Even though the perming process seems complete when the client has left the salon, the hair continues to form new bonds for two or three days. It is important that the hair should not be shampooed during those few days: shampooing may interrupt this 'curing' process and spoil the carefully constructed curls, or even lead to hair breakage.

Moreover, if the perm has not been neutralized completely, using a shampoo (whatever the brand) may cause the perm to fail disastrously. This is not the shampoo's fault, nor is it the client's.

It is wise to advise a client, however thrilled she may be with her newly permed hair, that her hair needs conditioning
regularly, especially thoroughly, and very frequently.

HAIR FACTS

Skin: acid and alkaline After any hair care procedure, we need to consider how the skin is left, and in particular how acid or alkaline it is. The pH of the surface of normal skin is between 5 and 6. That is, it is slightly acid. This is often referred to as the skin's 'acid mantle', but this is more of an emotional than a strictly scientific statement. The acidity is due in part to the sebum, the natural oil produced by the skin, which is itself slightly acid. One important function of the skin is to protect the tissues lying beneath it. The skin does this by acting as a barrier, regulating liquid loss from inside and keeping excess liquid outside the body. It also protects the body from infection. The acidity of the skin surface slows down the growth of bacteria and makes it harder for them to enter the body. If the acidity of the skin is affected - if the pH rises above 5-6, say - infections are more likely. This can happen if the pH is not adjusted after chemical hairdressing processes such as perming, by very thorough rinsing and careful neutralization.

Relaxing (straightening) hair

Relaxing is the opposite of perming. It is traditionally used by people with Afro-Caribbean hair to straighten their hair. It is popular because it makes hair easier to manage.

This lady's hair has been gently relaxed

The chemistry of the relaxing process is identical with that of perming, with the breaking of disulphide linkages and re-forming of the hair shape (in a straighter arrangement this time, rather than in curls), followed by re-making of the linkages.

The oval (elliptical) shape and natural crimp of Afro-Caribbean hair makes it difficult to straighten without damage. The chemical treatment can weaken the hair structure, and breakage after relaxation treatment is not uncommon. Contributing factors include incorrect concentrations of relaxing solution, mistakes in timing the application, and incomplete rinsing. Often the hair breakage is seen at the back of the neck. In addition, straightening leaves the hair fibers in a high degree of torsional stress (twisting), and a slightly wavy look. This makes them liable to rapid weathering, with the cuticle wearing down at the ends of the cross-sectional ellipse and a characteristic lengthwise splitting.

Hair breakage at the back of the neck associated with relaxing and traction

Grossly over-permed hair: repeated perming will produce dry, damaged hair unless very expertly performed

Perming different types of hair

Fine Caucasoid hair is probably the 'worst' hair to try to perm. It has the smallest diameter, and needs the minimum amount of perming solution and processing time. The photograph above shows you what the results of over-perming can be!

Strong, dark Caucasoid hair will take a perm reasonably well, even when tightly wound formers are not used.

No comment needed!

Problems in perming and straightening

In some countries, up to 70% of women have permed hair, in order to give their hair curl and body. In expert hands, perming can create wonderful effects. And it is a tribute to the skill of stylists and technicians that so many perms are successful and attractive, despite all the complexity of the chemistry and science of perming.

Unfortunately, not all hair is suitable for perming - and so many clients with thinning hair seem to want a perm! - let alone the delicate question of whether the style that has charmed the client will in fact suit her. The table below shows some problems that can arise with perming.

• Although some of the disulphide linkages re­form during neutralisation, a proportion fail to do so and remain broken. The hair is thereby weakened.
• Where the cuticle scales fail to close up tightly again after perming, the hair is left with a roughened surface and weathers more quickly.
• Incorrect application of perming, straightening or relaxing solutions can dissolve the hair fibres or lead to breakage, usually quite close to the scalp. This kind of breakage almost never happens on the same day as perming. It is believed to be the result of either over-perming or poor neutralization.

Permanent waving process variability: the factors to be considered before perming
Hair stock	Hair type	Hair history	Perm process			Post perm
			Reduction	Rinse	Neutralise
Caucasian	Dry	Perm	Chemistry	Time	Chemistry	Advise
- Northern Europe	Greasy	Color	- acid		- age of product
- Latin	Normal	Bleach	- alkaline	Temperature	- concentration	Warm water
- Indian	Mixed	Weathered	- age of product		- temperature of solution
Asian			- concentration	Volume	- ambient temperature	Perm type/style
- Chinese	Curly	Normal	- temperature of solution		- time to apply
- Japanese	Straight	Mixed	- ambient temperature		- time to work	Product use
			- time to apply		- pre-wet
	Long		- time to work		- post-wet	Activity
African	Short		- pre-wet		- solution:hair mass ratio
			- post-wet
	Thick		- solution:hair mass ratio
	Thin
			Curlers
	Coarse		- size
	Medium		- type
	Fine		Hair tension