Effect of Bleaching on the Streaming Potential of Human Hair
The streaming potential method reveals the changes of the hair surface upon hair treatment processes and supports the optimization of cosmetic products.
The importance of cosmetic products, especially for hair treatment, has reached an enormous dimension in the last years. The development of hair care products and the demand for improved formulations require the understanding and control of different hair treatments such as the application of shampoo and conditioner, bleaching or coloration.
Besides the different behavior of virgin hair, the different acceptance of hair care products due to a permanent modification of the hair structure by bleaching introduces another challenge for the cosmetician.
Streaming potential measurements at pH 5,9 (below) show the effect of the bleaching agent on the human hair and correlate with the degree of bleaching.
The high negative streaming potential for virgin hair indicates the hydrophobic property of an untreated natural hair surface. With increasing degree of bleaching the natural hair structure becomes more destroyed through breaking the R–S–S–R1 bonds of cystine and oxidation of the remaining sulfide groups. Water penetrates into the more open and hydrophilic structure of bleached hair and the negative streaming potential decreases.
The knowledge of the streaming potential (zeta potential) of bleached hair is the basis for the investi-gation of a subsequent hair treatment by different hair care products.