lower charge density polymer yields higher tress stiffness than the higher charge density polymer at 50% RH, but this trend is reversed at 90% RH. A hypothesis is offered in explanation of this phenomenon, relating adhesion and cohesion to the performance of fixative-hair composites. At high humidity, moisture can plasticize the polymers, reducing the cohesive strength, so electrostatic attraction and thus adhesion becomes the dominant force. Evidence to support this hypothesis is given.