Redken Laboratories Inc.

L'avant Garde, Inc.

Hayel M Said

Roger A Mathews

Hian Said

Leroy D Hunter

The condition of hair or other keratin fibers can be evaluated by measuring the force required to obtain a first value of elongation of the fiber in the yield region of the force-elongation curve, and the force required to obtain a second value of elongation of the fiber in the yield region. The ratio of these two measured forces is then determined as a damage index for the fiber. It is found that a constant force ratio is obtained for wet virgin keratin fiber independent of fiber diameter or the source of the fiber. It is also found that the force ratio changes as a function of subjective or objective measures of chemical damage to the hair fiber. The force ratio or damage index can, therefore, be used for identifying hair care products suitable for application to the hair without inducing unacceptable damage. The tests may be performed with simple tensile testing apparatus without tedious examination of the hair under a microscope.

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Simi Valley, CA, United States of America

Hayel M Said