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Comparatively Speaking: Temporary vs. Permanent Hair Color Systems
By: Anthony J. O'Lenick Jr., Siltech LLC, and Nick Morante, Nick Morante Cosmetic Consulting
Posted: July 10, 2012
page 2 of 2
The colorants utilized are conventional cosmetic colors such as FD&C Blue No. 1, FD&C Yellow No. 5 and D&C Red No. 33. These colorants are not considered reactive or oxidative dyes. Using these primary colors in the correct proportions, a brown dye can be created as well as shades in between. The trade-off is that although they do not last as long as permanent hair dyes, they are safer to use.
Permanent Hair Color
In the permanent hair dying process, hair lightening or bleaching (usually with hydrogen peroxide as the primary oxidizing agent) is used to lighten the hair and remove the original color prior to the dying process. The bleach reacts with the melanin in the hair shaft removing the color in an irreversible chemical reaction. The bleach oxidizes the melanin molecule, and although the melanin is still present, the oxidized molecule is now colorless. The hydrogen peroxide breaks chemical bonds in the hair, which releases sulfur that accounts for the characteristic odor of the hair coloring process.
The outer layer of the hair shaft, or cuticle, must be opened with ammonia before permanent color can be deposited into the hair. Once the cuticle is open, the dye reacts with the inner portion of the hair or cortex to deposit the color. This process essentially damages the hair.
Permanent hair colors or coal tar hair dyes are oxidative and use a two-step simultaneous reaction that first removes the original color from the hair and then deposits the new color. It is the same process as lightening, except that color is chemically bonded within the hair shaft. Conditioners close the cuticle after coloring to seal in and protect the new color. This type of hair coloring system can last weeks or until the system is reapplied to begin the coloring process again. An example of a permanent hair dye is phenylenediamine (PPD) (CAS# 105-50-3).
Other organic compounds are responsible for creating different hair dye colors. These ingredients are called couplers. Blue hair dyes include 1,3-diaminobenzene (CAS# 25265-76-3) and its derivatives. Shade variations for all hair dyes are based on different reaction products. Red hair dyes include 3-aminophenol (CAS# 591-27-5), 5-amino-2-methylphenol (CAS# 2835-95-2) and 1-naphthol (CAS# 90-15-3). The combination of 2,5-diaminotoluene (CAS# 95-70-5) with 3-aminophenol gives a magenta-brown dye, while the combination of 2,5-diaminotoluene with 1-naphthol gives a purple dye. Yellow-green hair dyes include resorcinol (CAS# 108-46-3), 4-chlororesorcinol (CAS# 95-88-5) and benzodioxoles (CAS# 274-09-9). These compounds produce broad-band absorption when they react to form colors, allowing for more natural-looking hair colors. The combination of 2,5-diaminotoluene with the coupling agent resorcinol gives a greenish-brown dye. These chemicals are all highly reactive and can be extremely hazardous to use. They can burn the skin or cause irritation, and can be extremely toxic to some individuals.