Basic Theory of Hair Color

All artificial colors are based on one, or more, of the three primary colors: red, blue and yellow. These form the basis of the color circle. The other colors on the circle are produced when the primary colors are mixed together.

Examples: yellow+ blue = green, blue+red = purple, etc. Opposite colors on the circle neutralize each other, e.g. blue neutralizes orange and green neutralizes red.

A blue based shade should not be applied to hair with yellow tones as it could result in a greenish cast. This is because green is positioned between blue and yellow on the color circle. The same happens if a red shade is applied to hairwith yellow tones. Result? An orange cast.

The problem for the colorist is that the dye-stuffs have a varying behaviour pattern:

1. Development Time. Some colors develop quicker than others. The potential development rate of the colors (from the quickest) is as follows:

  • Red
  • Orange
  • Yellow
  • Purple
  • Blue
  • Green

If a tint (which comprises a mixture of these colors) is under-developed there is a possibility of an irregular result. But, if the hair is given a full development time under normal conditions it will not over-develop. It is when the conditions vary, or the selection is incorrect, that the desired result will not be achieved.

2. Tenacity is the ability of the colors to grip and retain within the hair structure. It is interesting to note that, in order of tenacity, the colors are as follows: Green Purple Yellow-Blue Orange Red

Almost a reversal of the development rate! The texture of the hair must therefore be carefully considered before coloring. The finer textures take more readily—the coarser textures resist penetration.

It is important for the student colorist to learn the manufacturers\’ shade charts and understand the difference between shades and tones.

Tones determine the color of hair. A tone is a variation of a shade, e.g. Dark Blonde, Dark Ash Blonde and Dark Reddish Blonde.

Shades determine the depth of color. The ten shades are: blue-black, black, dark brown, mid brown, light brown, dark blonde, mid blonde, light blonde, very light blonde and white.

Another point, on which I feel particularly strongly, is that you should have a basic knowledge of the chemical substances in the products being used. The professional colorist must be aware of the damaging effect they could have on the hairif used incorrectly.

pH Scale

The pH scale is a chemical gauge which determines whether\’ a product is acid or alkaline (see diagram). pH 7 is the half-way point on the scale and is said to be neutral. From pH 6.9 down to 0.1 the scale measures acids—the lower the product reads the more acidic it is. Conversely, from pH 7.1 up to 14 the scale measures alkalis and the higher the product reads the more alkaline it is.

The pH of a product is determined by its active working substances. In refined products, a careful chemical balance is usually achieved and essential active materials are \’buffered\’ with other ingredients to prevent damage to the hair or skin.

The pH scale can become complex when used by chemists to measure a product—every number is a logarithmic scale often. This means that pH 6 is ten times more acidic than pH 7 and . . .

  • pH 5 is 100 times more acid than 7
  • pH 4 is 1,000 times more acidic than 7
  • pH 3 is 10,000 times more acidic than 7
  • pH 2 is 100,000 times more acidic than 7
  • pH 1 is 1,000,000 times more acidic than 7

It may sound frightening when I say pH 1 is one million times more acidic than pH 7 but everyday foods, for instance, often have a very low pH. Example: Orange juice has a pH of 2. The contents of the stomach, which contain hydrochloric acid, can measure as low as pHl!

On the alkaline side of the scale . . .

  • pH 8 is 10 times more alkaline than 7
  • pH 9 is 100 times more alkaline than 7
  • pH 10 is 1,000 times more alkaline than 7
  • pH 11 is 10,000 times more alkaline than 7
  • pH 12 is 100.000 times more alkaline than 7
  • pH 13 is 1,000,000 times more alkaline than 7
  • pH 14 is 10,000,000 times more alkaline than 7

If you compare pH 1 to pH 13 you will find that it is ten billion times more acid. Conversely, pH 13 is ten billion times more alkaline than pH 1!
The most accurate way of reading pH is with a pH meter. This comprises electrodes which measure the concentration of hydrogen ions on the alkaline side. An ion is an electrically charged atom—ions are attracted to the two types of electrode on a pH meter: cathode and anode. The balance of readings from these two electrodes gives the pH reading.

The pH of hair and skin is determined by the sebum and sweat which make up the acid mantle. The actual pH of hairand skin varies from one person to another but will generally be acid at a pH of 4.5 to 5.5.

Tints and bleaches are always alkaline and cannot work on the outer part of the hair structure—they have to penetrate the hair shaft. How? These products have to open the cuticle of the hair shaft to enable active materials to penetrate to the inner part of the hair. This is only possible if the products are alkaline. The concentration of alkaline materials and other \’buffer\’ ingredients determines how long the penetration and opening of the hair will take. If this process is carried out too quickly, hair damage will occur.


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