Adsorption Properties of Hair 364 lubrication to enhance feel and facilitate manageability. Yet the dramatic influence of water on the properties of hair demonstrates the potential for manipulating the fiber bulk. To date, alteration of hair’s internal properties has involved reactive routes, but simple, reversible adsorption processes are clearly observed to have major effects. Water is a plasticizer for hair. Its polar nature disrupts hydrogen bonds and salt bridges that provide secondary structuring within fibers. But the extent of this affect depends on concentration within the hair, and this parameter alters constantly with the relative humidity of the environment. Therefore, the properties of hair are not constant, and the dimensions, stiffness, and conductivity are all at the mercy of climatic conditions. Thus style retention becomes an issue at elevated humidity when diminished stiffness prevents the fibers from supporting their own increased weight. In addition, fiber strength is lessened, and increased swelling leads to reduced feel properties. Meanwhile, static flyaway is a problem when low water content hinders the ability to dissipate charge buildup. This said, the ability to alter the moisture content, or finding molecules that provide a comparable effect, affords the potential to free ourselves of this dependence. Preliminary efforts in this area appear promising yet it is clear that penetration of materials into hair is often a slow process. Heat is an ally, but nonetheless, conventional product forms would not appear to be a suitable vehicle for best delivering these benefits. The substantial literature on the effects of moisture in a variety of related materials provides both background and a springboard for activities in this area. However, it also serves as an indication of knowledge gaps pertaining to our own substrate of choice. Namely, there is very little independent, fundamental knowledge about penetration and retention of potentially salutary materials in hair. As such, this would appear to be an exciting topic with much to be learned and the ultimate potential for innovative products with new and novel benefits.