Advances in Hair Styling 444 the product is evaluated in its entirety, from the product package (dispensing the product), product form (distribution through hair), styling process (tack phase), ease of styling, compatibility with styling tools, and end result (the stiffness, shine, etc.). Evaluations are typically half-head versus a control formulation. The control formulation may be an internal or commercial benchmark. Full head evaluation may be used for new technology/product concept testing when there is no suitable benchmark. Salon tests are designed to closely approximate actual conditions of styling usage, yet yield some degree of control and objectivity to maintain the scientific principles of the study design and data analysis. Salon results with statistical analysis may be used as product claims substantiation. The evaluation commences with well-defined attributes with which the evaluator has been trained to discern degrees of difference. During application, the stylist evaluates wet parameters which may consist of attributes such as product spreading, tackiness, and wet combing. Upon completion of the wet evaluation for both sides of the head, the stylist then evaluates the dry hair parameters such as stiffness, shine, smoothness, style memory, volume, combing, and residue. Evaluations are tabulated and results with statistical analysis are reported. Consumer home use testing: The last phase of the styling product evaluation is consumer use studies. Data collected up to this point from instrumental, trained panel, and salon studies has been controlled with application dosage amount, environmental conditions, and designed criteria for evaluation. This step is critical to reflect consumer opinion because often results from trained panelists and instrumental analysis are not perceived by the consumer, or attributes that have not been measured or evaluated in salon or lab tests are key attributes for the consumer.43 Trends Hair products: Over the course of the last century, formulators have developed different hair care categories, e.g. shampoo,