Thursday, December 22, 2011

Hair Colors

Why coloring hair
Because it is the one thing that can dramatically change our appearance If we don't like the way we look! Also, it is quite fun to change it. I do agree that most of the time we look the best with our natural color. There are few reasons that why we want to dye hair,
(1) We want to lighten  our hair more than three shades,
 (2) We have dark hair and want to dye to make them light or ,
(3) We have natural light  brown or blonde hair and want to dye it,
(4) We are re trying to fix a problem,
(5) We have light hair and want to make it darker.
(6). Many people think that gray is the first sign of aging and the end of his youth, so they go for hair coloring.

Natural hair dyes
Hair dye is one of the oldest known beauty preparations, and was used by ancient cultures in many parts of the world. Records of ancient Egyptians, Greeks, Hebrews, Persians, Chinese, and early Hindu peoples all mention the use of hair colorings. Early hair dyes were made from plants, metallic compounds, or a mixture of the two. Rock alum, quicklime, and wood ash were used for bleaching hair in Roman times, and herbal preparations included mullein, birch bark, saffron, myrrh, and turmeric. Henna was known in many parts of the world; it produces a reddish dye.
Many different plant extracts were used for hair dye in Europe and Asia before the advent 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, and this is still used in many modern hair preparations. The bark, leaves, or nutshells of many trees were used for hair dyes. Wood from the brazilwood tree yielded brown hair dyes, and another hair dye known in antiquity as fustic was derived from a tree similar to the mulberry. Other dyes were produced from walnut leaves or nut husks, and from the galls, a species of oak trees. Some of these plant-derived dyes were mixed with metals such as copper and iron, to produce more lasting or richer shades.
Synthetic hair colors or dyes
In general, hair dyes include
The dye chemicals are usually amino compounds, and show up on hair dye ingredient lists with such names as 4-amino-2-hydroxytoluene and m-Aminophenol. Metal oxides, such as titanium dioxide and iron oxide, are often used as pigments as well.
Modifiers stabilize the dye pigments or otherwise act to modify the shade. The modifiers may bring out color tones, such as green or purple, which complement the dye pigment. One commonly used modifier is resorcinol, though there are many others.
Antioxidants protect the dye from oxidizing with air. Most commonly used is sodium sulfite.

Alkalizers are added to change the pH of the dye formula, because the dyes work best in a highly alkaline composition. Ammonium hydroxide is a common alkalizer.
5.soaps, .ammonia, wetting agents, fragrance, and a variety of other chemicals used in small amounts that impart special qualities to hair (such as softening the texture) or give a desired action to the dye (such as making it more or less permanent).
The developer is most often based on hydrogen peroxide, with the addition of small amounts of other chemicals depending on the manufacturer.

Temporary Hair Dye
Temporary or semi-permanent haircolors may deposit acidic dyes onto the outside of the hair shaft or may consist of small pigment molecules that can slip inside the hair shaft, using a small amount of peroxide or none at all. In some cases, a collection of several colorant molecules enter the hair to form a larger complex inside the hair shaft. Shampooing will eventually dislodge temporary hair color. These products don't contain ammonia, meaning the hair shaft isn't opened up during processing and the hair's natural color is retained once the product washes out.

Semi-Permanent Hair Dye
This product adds color without changing natural color dramatically. The hair color contains tiny color molecules that enter the hair's cuticle, or outer layer, and go into your hair's cortex. They don't interact with your natural pigments. And since the molecules are small, they eventually exit the hair shaft after several shampoos, leaving the hair as it was before treatment.
Permanent Hair Dye
 Permanent Hair Dye  molecules enter all the way into the cortex, where they react and expand to a size that cannot be washed out. These dyes acts to lighten the hair's natural pigment to form a new base and then to add a new permanent color.

Structure of Human hair

Hair is made of strong elastic strands of protein called keratin and in chemical terms is composed of oxygen, iron, nitrogen, hydrogen, sulphur, carbon and phosphorus.   

Each hair is constructed in three different layers: the cuticle, the cortex and the medulla.
The cuticle is the outermost layer of the hair which provides protection to the inner cortex layer.  Improper care and frequent use of harsh chemicals on hair damage the cuticle.

The cortex is the second layer.  . The cortex is composed of fibres twisted together like a rope. It is the cortex which gives the hair its colour. The presence of the four natural pigments black, brown, yellow and red are logged in the cortex in varying proportions, and the air spaces in the cortex determine the colour and shade of hair.  
Lastly, the medulla is the unimportant innermost layer which is composed of soft keratin..  

How hair colors work

The outer layer of the hair shaft,(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 (usually occurring simultaneously)
  1. First removes the original color of the hair
  2. Second deposits a new color.
 Ammonia is the alkaline chemical that opens the cuticle and allows the hair color to penetrate the cortex of the hair. It also acts as a catalyst when the permanent hair color comes together with the peroxide.
The developer( peroxide) removes pre-existing color. Peroxide breaks chemical bonds in hair, releasing sulfur, which accounts for the characteristic odor 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 conditioners close the cuticle after coloring to seal in and protect the new color.

Health risk and hair colors

Use of hair dye has been linked to allergic reactions, respiratory disorders and even cancer. Harmful ingredients used in hair color and hair dyes ,Hair dyes contain heavy metals that can be harmful. Ingredients in hair dyes are toxic and cause irritation to the eyes, skin and mucous membranes to hypersensitive people.  

  • Para-phenylenediamine and tetrahydro-6-nitroquinoxaline, both have shown to damage genetic material and cause cancer in animals. Allergic reactions from PPD are known to cause facial and neck swelling. Inhalation is likely to bring about coughing, sneezing and shortness of breath, and respiratory problems in extreme cases. Skin contact with PPD may cause rashes and eye contact irritation, redness and pain.
  • Coal tar, a known carcinogen is used in hair colors and dyes as it creates brighter and more lasting colors than other organic vegetable dyes.
  • Formaldehyde is a preservative linked to cancer, developmental and reproductive toxicity and more.
  • DMDM Hydantoin, another preservative is a known immune system toxin (and has been restricted for use in cosmetics in Japan).
  • Eugenol is a fragrance ingredient that’s associated with cancer, immuno toxicity, neuro toxicity and allergies
  • Ammonia exposure to high levels of ammonia can cause irritation and allergy, hair loss problems and scalp dermatitis.
  • Hydrogen peroxide Hydrogen peroxide bleaches your hair and thus damages it. But the extent of the damage will depend on its level of concentration..
Further readings

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