A new approach to the bending properties of hair fibers.

A new test developed to characterize the bending properties of treated or virgin hair fibers is described. The device consists of a pendulum that bends a sample made up of 39 parallel hair fibers at each swinging stroke. Hair bending stiffness can be assessed by the number of strokes observed until the pendulum stops. The mechanical behavior of natural hair fibers is related to their geometric characteristics. The effects of various hair treatments can be assessed by this method.

Contribution to the quantification of the conditioning effects of hair dyes.

Synopsis Apart from the problem of colour, the cosmetic properties of hair after dyeing play a vital role both for the cosmetic chemist and the user. A methodology for a quantitative assessment of these conditioning effects is proposed. This methodology is based on a realistic approach to the protocols, and uses original apparatus and accessories which take the particular context of the dyeing process into account. Particular importance is given to studying the length of set hold and the ease of combing. Big differences were observed between three dyes on sale on the market, including their finishing treatment products such as shampoo or rinse.