Advances in Hair Styling 442 Volume: This hair attribute is highly sought-after by consumers. Ring/radial compression methods have been used to measure hair body, in which volume is a key component. In this method, a hair tress is pulled through a ring of different radial dimensions. The force required to do this is presumed to provide a measure of volume or body.38 Method development in hair volume as an attribute of hair styling has progressed significantly with quantifiable measurement techniques. For example, two advanced methods that have been developed include a controlled mechanical styling component employing the use of laser stereometry39 and image analysis of two-dimensional spatial arrangements of tresses, mannequin heads, or styles from live panelists. Smoothness: Coefficient of friction of styling product films may be assessed using a slip peel tester, where the movement of a sled over a stationary styling polymer film measures force vs. distance and allows for the calculation of static and kinetic coefficient of friction. More recently, the atomic force microscope (AFM) has become an important tool for studying the micro-/nano-scale surface architecture of styled human hair. Nanotribological properties such as roughness, friction, and adhesion from styling products can be observed through AFM. AFM has been used to evaluate the film properties of styling treatments on the hair surface and can be operated in a controlled climate chamber in order to study the effect of temperature and humidity on various physical properties.40 Using a nanoindentor, a nanoscratch experiment may be performed by applying a constant vertical force and a constant lateral velocity. The coefficient of friction is determined as the ratio of lateral force to normal force monitored during nanoscratching.41 Shine: In assessing the finished style, shine (or matte finish for some stylers) is a key claimed attribute. A smooth cuticular surface and fiber alignment increases specular light reflectance, displaying a visible reflectance “shine band” on hair, and increases perceived shine. When evaluating shine, it is best to conduct the evaluation in a controlled light box where lighting is uniformly distributed and the source for light has several options, such as daylight or