The pendulum instrument (made in TRI) allows twisted fibres to untwist. The speed and force by which the pendulum rotates is a measure of hair flexibility and softness.
Hair Flexibility and Softness
If you want to show that hair is harder to bend, because you want to deliver greater style hold, or if you want to show that it is or easier to bend, because you want to deliver greater hair softness and pliability, then it is useful to perform torsion experiments.
Torsion experiments involve attaching a weight to one end of a hair fiber and then gently twisting it. When the fiber is released it untwists itself, rotating backwards and forwards. The speed and force by which the fiber untwists itself is a measure of the hair’s pliability and elasticity. Torsion experiments are most sensitive to changes in the hair cuticle. These experiments have been used to show the hair softening effects of moisture and hair treatments, such as hair oils.