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Transcription

1 Slide GH11.3.1

2 GH The physical effects of setting on the hair structure - (1 of 2) Hair is made up of polypeptide chains that twist together to form hair as we know it. These chains are held together by strong disulphide bonds, weak salt bonds that help to hold the chains together and weak hydrogen bonds that prevent the loops of the polypeptide chain spirals from being stretched too far. When hair is in its normal state it is not stretched. This state is known as the alpha-keratin state. When hair is stretched as during setting it becomes beta-keratin. If hair is wet and/or heated it is easier to stretch and it will stretch further than when it is dry. This is because the hydrogen bonds and some salt bonds are broken by the moisture or the heat so the springs (the shape of the polypeptide chains) can be lengthened. When hair is set it is stretched slightly by the rollers. Because it is dried into this stretched position the broken hydrogen and salt bonds reform in a different pattern and will stay there until the hair becomes wet or hot again. This is what gives set lasting power. When hair becomes wet again: by absorbing atmospheric moisture by shampooing being in a steamy bathroom excessive scalp perspiration being caught in the rain being outside on a foggy day being in a humid climate the hydrogen and salt bonds will go back to their normal pattern and the blow-dry will be lost.

3 Slide GH11.3.2

4 GH The physical effects of setting on the hair structure - (2 of 2) Summary: when hair is in its natural, unstretched state, it is Alpha keratin when hair is wet and stretched slightly setting becomes Beta keratin if the hair is dried into this stretched shape it remains Beta keratin when it becomes wet again when it reverts to its normal, unstretched shape and goes back to being Alpha keratin when the hair is dried into a stretched shape it keeps this shape because the hydrogen and the salt bonds reform into a different pattern Notes

5 GH How the incorrect application of heat can affect the hair and scalp Hairdressers must be aware of the dangers involved in the use of heated styling tools and equipment. If care is not taken there is a danger of: damaging the cuticle causing the hair to break burning the scalp discolouring the hair Notes. If a hand dryer or other heated equipment is held at one area of the scalp or hair for too long or is held too close to the hair or scalp it is likely to burn. The least that will happen is that damage to the cuticle will occur but the hair may break off completely. Hair that is naturally white or that has been chemically treated will discolour if too much heat is applied to it. White hair or bleached hair will become yellow, African Caribbean hair will become reddish and chemically treated hair may fade in colour. How can you prevent too much heat from being applied to the hair or scalp?

6 GH Why hair should be allowed to cool before dressing When hair has been wet and heated during a set the hydrogen bonds and some of the salt bonds will have been broken. To ensure that the set will last, the hair must be dried under tension so that the bonds can reform in a new pattern. Because heat, as well as water, causes the hydrogen and salt bonds to break, the hair should be left in rollers or pincurl clips until it cools. By doing this it allows the bonds to set into their new shape. Remember that the hair must be stretched to let the bonds reform in a new shape. If you take the tension off while the hair is still warm some of the bonds will reform in their usual, unstretched, alpha-keratin state. It is not always necessary to hold the hair for a time while it cools, simply switch the dryer to cool, this will complete the process quickly and without wasting time. If heated equipment such as tongs or straighteners are being used avoid disturbing the hair until it cools, leave it in the styled shape and allow it to cool naturally. If you brush or comb the hair or even position it with your fingers before it has the chance to cool the bonds will reform in their natural shape. Summary There are two main reasons why hair should be allowed to cool before finishing the dressing: to achieve a longer lasting effect to allow the hydrogen bonds to harden into their new position Why hair should be kept damp during the setting process In order to achieve a style that is different to the client s natural look you must make the hair take on a new shape. You must change the position of the bonds in the hair from alpha keratin to beta keratin. This is done by wetting, heating and stretching the hair slightly while drying it into its new shape. If you allow the hair to dry without having it under tension (stretching it) the hydrogen and salt bonds will simply take their normal, unstretched, alpha-keratin position as the hair dries. If the hair is dry, even if you heat the hair, you would have to heat it to quite a high degree before you could cause the bonds to move into a new, beta-keratin pattern. When hair is wet: it stretches more than when it is dry you can achieve a smooth effect the hydrogen and salt bonds can be reformed into a new shape to produce a style.

7 Session 3 GH11 Set and dress hair Learner Check Session 3 1. Hair is hygroscopic what does this mean? 1 2. State the types of hair that are likely to be porous Describe the changes that occur in the hair structure during setting 3 4. What happens to the hair structure when hair becomes wet again after a blow dry? 5. State how the incorrect application of heat can affect the hair and scalp Why should hair be allowed to cool prior to dressing out? 6 7. How do heat protectors work? Se 7