The structure of hair can be divided into three parts: epidermis, cortex and medulla.

1. Epidermis: about 10%. It is the coat of hair, which protects the head in scales, and the coarse luster of hair depends on this layer. The more layers of hair scales, the thicker and harder the hair. Generally 3- 15 floors. This floor

2. Cortical layer: It accounts for about 80% of hair and is made of keratin. It contains a lot of natural pigment particles, and the cortical layer reflects the color of hair. Dyeing and perming all work on this floor.

3. Myeloid layer: about 10%, which mainly absorbs nutrients from the scalp for hair growth and has no effect on hair dyeing and perm.

2. Hair growth cycle and formation of natural hair color

Healthy hair grows at the rate of 1-2cm per month, but it will not grow permanently. There is a growth period, a development period and a death period. A hair has a life span of 2-7 years, and it will fall out after this life. Hair grows in the hair root near the papilla, where there are many embryonic cells, including a group of embryonic cells responsible for producing natural pigment body-melanin, which is transferred to daughter cells, which eventually form a part of the cortex, so hair has a natural color when it grows.

Melanin, also known as natural pigment body, consists of two kinds of natural pigment particles.

1, dark brown pigment particles

2, yellow and red pigment particles.

All natural hair colors are formed by the ratio of these two natural pigment particles. Europeans have more yellow and red pigment particles and less dark brown pigment particles, while China has more dark brown pigment particles.

Three. Classification of hair

1, neutral: the sebaceous glands of the papilla at the hair roots secrete moderate oil and water, and this kind of hair dyeing is easy to master and accurate. 2, oily: the sebaceous glands of the hairy root nipple secrete too much oil and water, which makes it difficult to color this hair.

3, dry: the sebaceous glands of the hairy root nipple secrete too little oil and water, and this kind of hair is easy to change color.

4. Damage: the hair is bifurcated, not supple, not supple and porous. The main reason is that there is something wrong with the epidermis, the hair scales fall off and it is easy to change color and fade.

5, resistance: the hair is thick and hard, with many scales, which is not easy to color.

4. Classification of hair dyes

1) temporary hair dye

Temporary hair dye is a kind of hair dye that can remove the color from hair only by washing it with shampoo once. Because the particles of these hair dyes are too big to enter the hair shaft through the epidermis, they just deposit on the hair surface to form a colored covering layer. In this way, the interaction between dyes and hair is not strong, and it is easy to be washed off by shampoo.

2) Semi-permanent hair dye

Semi-permanent hair dye generally means that it can resist 6- 12 shampoos before fading. Semi-permanent hair dye is applied to the hair, and after staying for 20-30 minutes, it can be washed with water to color the hair. Its principle of action is that dye molecules with relatively small molecular weight penetrate into the hair epidermis and partially enter the cortex, which is more resistant to shampoo cleaning than temporary hair dyes. Because no hydrogen peroxide will damage hair, it is more popular in recent years.

3) Permanent hair dye

There are three kinds of permanent hair dyes: plant permanent, metal permanent and oxidation permanent.

1. Plant persistence:

Dyeing with substances extracted from the stems and leaves of plants is expensive and rarely used in China.

2. Durability of metal: Dyeing with metal raw materials is mainly deposited on the dry surface of hair, and the color has a dull metal appearance, which makes the hair brittle and the perm efficiency low.

3. Oxidation durability: The mainstream products in the market contain dye intermediates and coupling agents, which are generally not called dyes. After penetrating into the hair cortex, through oxidation, coupling and condensation reactions, larger dye molecules are formed and wrapped in hair fibers. Due to the different types and content ratios of dye intermediates and coupling agents, different color reaction products are produced, and the products of different colors are combined into different colors to dye different colors of hair. Because dye macromolecules are generated in hair fibers through the reaction of dye intermediates and coupling agents. Therefore, when washing, the formed dye macromolecules are not easily washed out through the pores of hair fibers.

Effect of formula composition of hair dye on hair dyeing and hair dyeing

The selection and proportion of (1) dye intermediates and coupling agents are directly related to the dyeing effect. Because each dye intermediate contains a small amount of isomers, the products produced by oxidation are complex and affect the effect, so the quality of dye intermediate should be guaranteed, that is, the purer the better. The ratio of dye intermediate and coupling agent is also the key to display the correct color.

(2) the content of free alkali in the dye

The alkali content in the dye is also very important, because the high alkali content is conducive to the penetration of dye intermediates into the hair, but it has a great stimulating effect on the skin, and because the intermediate coupling agent reacts under alkaline conditions, the oxidation reaction is incomplete. Moreover, the hair with low alkalinity is not easy to swell, and dye intermediates and coupling agents can not penetrate the hair well, resulting in uneven and incomplete dyeing effect. (3) the content of active substance hydrogen peroxide in the developer

The content of hydrogen peroxide directly affects the complete degree of oxidation reaction of dye intermediates in dyeing process. Low content, incomplete oxidation reaction and lighter color than planned. Under the influence of other media, it is possible to continue the reaction, resulting in unstable color after dyeing and failing to achieve the original effect. On the contrary, if the oxidation reaction is complete, but hydrogen peroxide has both oxidation and bleaching effects on hair, oxidation and bleaching may occur at the same time. High content will greatly enhance the damage to hair keratin, and it will also fail to achieve the ideal effect, and it is easy to fade after dyeing. Five: Introduction of color swatches

There are many ways to express colors, and the digital color coding system is the main one in the international market, which is adopted by most professional hairdressing factories in the world.

(1) chromaticity

Chroma is an index used to indicate how much melanin is contained in hair, and different shades indicate different shades of hair. Generally speaking, hair is divided into ten shades, which are represented by the numbers 1 to 10 respectively. The smaller the number, the higher the melanin content and the darker the color. Conversely, the larger the number, the less melanin and the lighter the color.

1) dark black, 2) natural black, 3) dark brown, 4) brown, 5) light brown, 6) dark gold, 7) gold, 8) light gold, 9) light gold 10) extremely light gold.

China people's hair is generally 1-3 degrees, the most common is 2 degrees, so the No.2 color is also called natural black, while Europeans' hair chroma is generally 4-6 degrees.

(1) Tone

Tone determines the specific color of a color.

Different manufacturers may have different shades and numbers. Our hue and numbers are as follows: 1) gray blue, 2) purple, 3) golden yellow, 4) copper, 5) bordeaux, 6) red and 7) green.

Example 1: dye paste color code 4.6

4- indicates that the chromaticity of the color is 4 degrees, that is, brown, and 6- indicates that the main color of the color is red. 4.6 The color of dye paste is reddish brown.

Example 2: Dye Paste Color Code 5.36

5- indicates that the chromaticity of the color is 5 degrees light brown, 3- indicates that the main tone of the color is golden yellow, and 6- indicates that the secondary tone of the color is red.

5.36 The color of dye paste is light red and golden brown.

(2) Enhanced colors:

Only hue has no chroma, and each hue has its own enhanced color.

There are two main functions:

1. When a color is not deep enough, adding it can deepen and strengthen a color.

2. Used to neutralize other tones and make them approximate gray.

Six: the principle of three primary colors and the process of color washing

When white light passes through the prism, it will be refracted into rainbow colors on the other side: red, orange, yellow, green, blue and purple.

1) Primary colors: Red, yellow and blue are called three primary colors because they cannot be mixed with other colors.

2) Secondary colors: orange, green and purple are all mixed by two primary colors. In fact, any imaginable color is a mixture of primary colors in different proportions.

3) Color wheel diagram: Primary colors and secondary colors can form a color ring to represent the relationship between colors. Clockwise, the color changes from light to dark, and the pigment particles change from small to large.

4) Contrast color: The opposite colors are mixed together to cancel each other out and become gray. For example, yellow can offset purple, green can offset red, and blue can offset orange, which is an important aspect of color characteristics. You may have an unsatisfactory tone or color after dyeing your hair. At this time, you can use the strong color of yellow tone to offset the unacceptable purple.

Wash your hair with hair bleach. Conceptually, blue is dark, red is medium and yellow is the lightest color. The darkest color in the hair is washed off first. Because the darker the color, the larger the volume of pigment particles, and the less the number of pigment particles in the cortex, which can only enter the surface part of the cortex. The lighter the color, the smaller the volume of pigment particles, and the more pigment particles in the cortex, which can enter deeper into the cortex. Therefore, the color of hair changes gradually during bleaching. Make the following changes: 1 23455 6789 10.

Blue, blue, purple, purple, red, red, orange, orange, yellow, light yellow.