Hair Dryers - Blow Dryer effects on Hair

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The World of Hair

an on-line reference by Dr. John Gray,
provided by the P&G Hair Care Research Center.
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		Page 80 -- BLOW DRYER EFFECTS ON HAIR

hair dryer has to be used to speed the process up. Heat is a great enemy to hair, however, and that means that dryers must always be used with great care and on a moderate setting. A hair dryer on its hottest setting will reach temperatures well above that at which water boils. As we have seen, this can have a disastrous effect on the hair. Using a 'hot oil' has a protective effect. So too do hair mousses, which contain specially formulated resins.
    Curls produced by setting are tight when they are first formed, but they can be brushed out into a lighter style. Using setting lotions or hair sprays gives a firmer effect, and helps to hold the temporary curl in for longer.
    Softer, looser styles can be created by brushing and blow drying only, without using rollers. The principle is exactly the same as that of the setting process. The only difference is that the hydrogen bonds re-connect to form the style that has been shaped by the brush.
    All hair gradually absorbs moisture from the air, and as the hydrogen bonds break it will in time lose its style - especially in damp weather!

setting curly hair

An excellent example of 'setting' to give a spectacular effect to already curly hair

HAIR FACTS

What happens during setting

First, read again the section in Chapter 1 of this book about the chemical structure of hair.
When hair is set, the millions of weak hydrogen bonds between the keratin chains in the hair are broken when the hair is wetted, and form up again in different places on the chains as the water evaporates during drying.
The strong disulphide linkages in hair can only be altered by chemical treatments, and are unaffected during setting. They keep the hair in its fundamental natural shape throughout repeated washing and drying.

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.

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