Semipermanent dyes

Semipermanent hair color products are formulated at an alkaline pH, usually between 8.5 and 10. At this pH the cuticle of the hair lifts away from the hair a Httie, allowing for easier penetration of dye. An alkyl amine buffered with an organic acid normally is used to obtain the desired pH. The formulations contain a mixture of solvents and surfactants to solubilize the dyes and a thickening agent is added so that the product stays on the hair without mnning or dripping. A 20—30 min appHcation time is normal for this type of product. A representative formula for a semipermanent dye product is given in Table 7. 

Hair dyeing includes the use of permanent, semipermanent, and temporary dyes. A permanent dye lasts through any number of washings as well as permanent waving. A semipermanent dye is removed after two to ten washings, and a temporary dye is largely eliminated after one washing. 

Hair dyes are of two types permanent and semipermanent. Permanent dyeing is achieved with a synthetic dye, applied with hydrogen peroxide that first bleaches the natural pigment melanin. Semipermanent dyes are generally made with vegetable extracts, such as henna, that coat rather than penetrate the hair shaft. There are a number of questions about the safety of synthetic hair dyes, since some of the products they contain cause cancer. 

ESSENTIAL INGREDIENTS OF OXIDATIVE PERMANENT AND SEMIPERMANENT DYEING SYSTEMS... 

Permanent or oxidation dyes Semipermanent dyes Temporary dyes or color rinses Other dyes... 

For forensic or commercial evaluations, light microscopy can readily determine whether or not hair of unknown history has been dyed with a permanent hair dye or has recently been dyed with a semipermanent dye. Human scalp hair does not generally contain pigment in the cuticle. Therefore, a light microscopic evaluation of fiber cross sections or even an optical section can readily reveal whether the hair in question has been treated with a commercial hair dye by determining whether the cuticle has been dyed. 

Semipermanent dyes are formulations that dye the hair without the use of hydrogen peroxide, to a colour that only persists for 4-6 shampooings. Temporary hair dyes or colour rinses aim to provide colour that is removed after the first shampooing process. 

Another important formulation in the cosmetic industry is that used for hair dyeing. Three main steps may be involved in this process bleaching, bleaching and coloring combined as well as dyeing with artificial colors. Hair dyes can be classified into several categories permanent or oxidative dyes, semipermanent dyes and temporary... 

Grollier, J. F. Process for preparing a composition for permanent or semipermanent dyeing of skin, eyebrows, lips or nails from a fluid under pressure, and dyestuffs. Eur. Pat. Appl. EP 1559392, 2005 Chem. Abstr. 2005,143, 179096. 

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