It's like a building set. Composed of several elements, assembled by putting them together to obtain a shape. If we don't like the shape, we dismantle the elements, move them around, reassemble them and create another shape. A set like this exists within the minute body of the hair, where the elements in question are molecules and the links chemical bonds.

It is the hair's keratin structure which enables it to adopt such a wide variety of forms.
This protein is a long chain of amino acids which in the hair is made up of four twisted chains running lengthways. Chemical bonds are established between the atoms in these chains which provide the cohesion of the whole, thereby giving the hair its natural form. By acting on these more or less resistant bonds, the hair's form can be altered in a temporary or more long-lasting manner.


The weakest of these bonds are the hydrogen , saline and hydrophobic bonds . Water, or even dampness, are enough to break them. When the hair dries, they reform according to the position the keratin chains have at that moment. When wet hair is given a particular form, the position of these chains is slightly altered. The bonds therefore reform in different places, maintaining the hair in its new shape.

So that if, for example, we go to bed with wet hair, this form will be haphazard, giving the hair an unkempt appearance. On the other hand, blow-drying or setting gives us control of the process so that, once dry, the hair will retain the form it has been given.

In both cases, this form is only temporary. The first reason is quite logical, since any renewed presence of water will result in breaking these newly formed bonds. The other reason is that there are other, more resilient bonds within the hair which will gradually give it back its original form. These are the bonds that must be altered if a more long-lasting modification of the hair's shape is to be achieved.

These other bonds are called "bridges", which is a clear indication of their resilience. They are disulphide bridges , acting on the sulfurated elements in the keratin . Resistant to water, they can only be broken by using chemical compounds. When they have been broken, the keratin chains can be moved and the hair becomes malleable. Hair considered too straight may then be curled - this is permanent waving. On the other hand, hair considered too curly or frizzy can be straightened out - this is uncurling. The result is made long-lasting by using another compound to re-establish the disulphide bridges according to the new position of the keratin chains, thereby determining the hair's new form.

- Permanent waving :
The disulphide bridges are broken down by reduction , by means of a slightly alkaline liquid known as curling liquid. They are reformed by a process of oxidation , using an acidic solution of hydrogen peroxide, the fixing liquid. The form is created by curlers, with the degree of curl being determined by their diameter.

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- Uncurling:
This technique of reduction and oxidation is also used to uncurl curled or frizzy hair. However, in this case the reducing agent is incorporated into a thick medium, making it easier to hold the hair straight during the period necessary for the reduction process to take place.
As for tightly curled or frizzy hair, they require the use of highly alkaline products such as sodium or potassium hydroxide. In order to protect the scalp, they are formulated in highly greasy creams. However, in contrast with other reduction agents, they will leave the hair weakened, with its elastic properties definitively lost.

  Yesterday and today

As time has gone by, these long lasting modifications to the hair have become extremely frequent and easy to apply. This has not, however, always been the case. The curling of wigs in the past - which were of course made from real hair - was obtained by rolling the locks around cylinders of earthenware, soaked for three hours in boiling water and then baked in an oven. A process known as "infernal curling"!
At the beginning of the 20th century, Nessler was the first to succeed in associating a chemical product with high heat to produce resistant curls on a human head.

The operation was very long, frequently resulting in the scalp suffering burns and many hairs breaking. The invention certainly worked, but people soon began to question the point of having a lasting hairstyle if it resulted in the hair itself being damaged. Researchers gradually improved their techniques and finally introduced cold permanent waving in the 1940's.

Improvements have continued to be made to the technique ever since. So that the seemingly incompatible requirements of efficiency, beauty and health may at last be associated.
This is why research into hair care is an endless process - but one that is certainly worth the effort. For in an age when personal appearance is a means of expressing singularity, what better way can there be of stating your own identity than by a fine head of hair?




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