The Anatomy and Chemistry of Hair and Hair Dye
Many different plant extracts were used for hair dye in Europe and Asia before the start of modern dyes. Indigo, known primarily as a fabric dye, could be combined with henna to make light brown to black shades of hair dye. An extract of the flowers of the chamomile plant was long used to lighten hair. The bark, leaves, or nutshells of many trees were used for hair dyes. Wood from the brazilwood tree yielded brown hair dyes. Another hair dye was derived from a tree similar to the Mulberry tree. Other dyes were produced from walnut leaves or nut husks. Some of these plant-derived dyes were mixed with metals, such as copper and iron, to produce more lasting or richer shades. Outside of the many colors that hair can be dyed, there are many different method used to color hair.
Hair dye and the hair coloring process is a matter of chemistry. The first safe commercial hair color was created in 1909 by French chemist Eugene Schuller. He used the chemical Paraphenylenediamine. Hair coloring is the result of a series of chemical reactions between the molecules in hair, pigments, as well as peroxide and ammonia. The choice of which method to use will depend on the desired shade and longevity of the color.
Temporary hair dye lasts for between one to three washes. This type of hair coloring involves no chemical reactions within the hair. Pigments are applied to the surface of the hair, without penetrating any further. These are easily removed by washing which is why people use them for experimenting without commitment. These dyes, although dependent on the color of hair being applied to, can be very brightly colored.
Semi-permanent hair dye lasts for between five and fifteen washes. These dyes are usually made from vegetable dyes and are mainly designed to penetrate just beneath the hair cuticle. No peroxide is present therefore no chemical reactions take place within the hair. But, pigments can be become trapped beneath the surface resulting in longer lasting color. These gradually wash out, but are able to provide brighter, more vibrant colors than are possible with permanent dyes. The effect of semi- permanent dyes can be greatly enhanced by pre-bleaching which opens the cuticles allowing greater penetration. Often after only a few washes semi-permanent dyes can fade but to increase the color’s longevity, one can reapply at this point before the color is completely diminished. This will cause the surface pigment to build up which intensifies the color.
Permanent hair dye lasts indefinitely. Hair either has to grow out or be chemically treated to remove color. Permanent hair coloring products often combine bleaching and coloring agents. The bleaching agent decolorizes the melanin and prepares the hair for coloring by expanding and opening the hair cuticles. Small dye molecules then enter the hair cortex where they react, increase in size and become trapped. This is how the hair strand is chemically dyed. The effect of permanent hair dye can last for as long as required, however the color can fade slightly over time.
Hair starts at the hair root, a place beneath the skin where cells band together to form keratin. Each strand of hair has two main components: the hair shaft and the root. The shaft is formed from the old cells that are pushed out as a result of new cell growth in the root. The parts of the hair are divided into three segments which include the cuticle, the cortex and the core. The cuticle forms the outer layer. It is made up of transparent, hard cells which overlap almost like scales. General hair condition is largely determined by the condition of the cuticle, since it gives hair elasticity and resiliency. The cortex forms the middle layer. The cortex is protected by the cuticle and consists of rope-like protein fibers. Damaged cuticles exposed the cortex which allows loss of moisture. When this happens the cortex unravels which causes split ends and damaged hair. The medulla is the core. It is the supporting structure for a strand of hair. The medulla can be absent or interrupted without weakening the hair strand. The natural color of hair depends on the ratio and quantities of two other proteins, Eumelanin and Phaeomelanin. Eumelanin is responsible for brown to black hair shades while Phaeomelanin is responsible for golden blond, ginger, and red colors. The absence of either type of melanin produces white or gray hair. Bleach is used to lighten hair. The bleach reacts with the melanin in hair, removing the color in an irreversible chemical reaction. The bleach oxidizes the melanin molecule. The melanin is still present, but the oxidized molecule is colorless. However, bleached hair tends to have a pale yellow tint. The yellow color is the natural color of keratin, the structural protein in hair. Also, bleach reacts more readily with the dark Eumelanin pigment than with the Phaeomelanin, so some gold or red residual color may remain after lightening. Hydrogen peroxide is one of the most common lightening agents. The peroxide is used in an alkaline solution, which opens the hair shaft to allow the peroxide to react with the melanin.
The outer layer of the hair shaft, its cuticle, must be opened before permanent color can be deposited into the hair. Once the cuticle is open, the dye reacts with the inner portion of the hair, the cortex, to deposit or remove the color. Most permanent hair colors use a two-step process which first removes the original color of the hair and then deposits a new color. It's essentially the same process as lightening, except the color is then bonded within the hair shaft. Ammonia is the alkaline chemical that opens the cuticle and allows the hair color to penetrate the cortex of the hair. Peroxide is used as the developer and breaks chemical bonds in hair which accounts for the smell of hair color. As the melanin is decolorized, a new permanent color is bonded to the hair cortex. Various types of alcohols and conditioners may also be present in hair color. The purposes of the conditioners are to close the cuticle after coloring to seal in and protect the new color.
Hair elasticity is the ability of the hair to be pulled or stretched out and returns to its regular shape without breaking or snapping. Elasticity is one of the primary indicators of your hair’s health. Healthy hair has a high level of elasticity, which gives it body, bounce and curl formation. The cortex contributes most significantly to elasticity because it is the portion of the hair structure that carries the bulk of an applied load. Hydrogen bonds are weak physical bonds that occur between hydrogen and amino acid nitrogen and oxygen atoms. These interactions are easily formed and broken and are responsible for a large portion of the elastic behavior of hair. For this reason, it is very important to maintain a proper amount of moisture inside the hair shaft. Lack of hydration would decrease hydrogen bonding which would affect the elasticity of hair strands. Diameter also influences the elasticity in hair. Hair of smaller diameter cannot withstand the same forces as hair of thicker diameter. This means that those with finer hair may have more trouble with their hair losing curl, not holding styles, and developing frizz and breakage. African hair typically has the smallest diameter, with Caucasian hair having medium diameter, and Asian hair having the thickest diameter. There is no way to change the hair’s diameter so one must just maintain the health of their hair.
Hair width measures the width of individual strands of hair but density refers to how closely those strands are packed together on a head. Hair's density can also be affected by hair texture, porosity and width. Awareness of hair density along with curl pattern, porosity and width, creates the ability to choose the right products, styles and cuts to maintain the volume of hair.
Porosity refers to how well your hair is able to absorb and hold moisture. It is affected by the flexible outer hair layer called the cuticle, which determines how easily moisture and oils pass in and out of your hair. Porosity can be affected by external factors such as exposure, heat treatments and chemical processing. Knowing your hair's porosity can help you choose the right products to keep your hair well-moisturized, supple, strong and shiny.
Regardless of if hair is straight, wavy, curly or overly curly we all have 3 basic textures. Those textures are fine, medium and coarse. Fine being the thinnest and coarse being the thickest. Texture is not how the hair feels but describes the thickness of each individual strand of hair.
Fine hair is the most fragile texture and can be easily damaged. People with finer hair tend to have more hair than people with thicker hair strands. Fine hair can tend to be oilier than other hair types. Also those with fine hair you may find difficulty holding a style. This is because hair is light and can often fall flat. Volume with fine hair is often desired but not often attained. Some other qualities of fine hair are inability to hold styles well, ability to become weighed down with heavy products, causing the hair to look stringy and ability to break easily because it’s fragile structure. Structurally, fine hair has two hair layers – a cortex and a cuticle.

Medium hair is the most common hair type and often covers the scalp very well. This hair texture is not as fragile as fine hair and can be manipulated into styles easily. Medium hair holds styles fairly well, usually looks thick and covers the fully covers the scalp and is not as prone to breakage as fine hair. Structurally, medium textures usually include the cortex and cuticle layers and may contain the medulla layer. The coarse hair texture is the strongest because structurally it contains all three hair layers – the cortex, cuticle and medulla. The medulla, the innermost layer of the hair shaft is a series of empty spaces. It’s an area filled mostly with air and protein. This hair texture usually takes longer to dry than others, and can be resistant to various chemical treatments. Coarse hair textures tolerate heat well and resist breakage better than the fine or medium hair. It has a full appearance and holds styles very well.

Works Cited
Milady. "Haircoloring." Milady's Standard Professional Barbering. N.p.: Delmar Cengage Learning, 2010. N. pag. Print.