Chapter 15 503 testing. Whenever possible the use of in-house, skeletal formulations is preferred. Without doubt, the largest source of variability associated with virtually all instrumental testing of hair products relates to the treatment procedure, where variation in the way a given product is used can outweigh formulation differences. For example, the deposition efficiency of conditioners will be highly dependent on factors such as product-to-hair dosage levels, residence time on the hair, and thoroughness of rinsing. As such, the generation of quality data necessitates standardizing and controlling each of these variables. Figure 5 shows wet combing results for conventional, commercially available rinse-off conditioner products that were generated by the standard methodology used at TRI-Princeton. As described earlier, sensitivity is improved by using bleached hair, which, for reference purposes, yields maximum load combing forces of around 60 grams in an unconditioned state. Therefore, all formulations are observed to dramatically lower grooming forces however, typical “moisturizing” conditioners tend to yield the greatest benefit due to being intentionally formulated with high Figure 5 Typical wet combing results for commercial conditioner products