Hair Testing: Opportunities & Challenges: A very personal view

Hair testing is an integral part of the research & development of hair cosmetic processes and products. This includes, namely, the support of associated marketing concepts. From rather modest beginnings based on wool science, hair testing today comprises a wide portfolio of bio-physical and –chemical experimental as well as theoretical methods, ranging from quite basic to very advanced techniques. Methods may be applied across all structural levels from molecular properties of specific hair proteins to the movement and appearance of hair collectives. Each method provides its primary set of information as well as possibly unexpected opportunities and challenges. For this presentation, the author will look at a number of seemingly standard and popular tests in the wider areas of thermal and mechanical analyses, for which he has a special interest. Namely for seemingly simple tests, theory development, kinetic and statistical analyses do not only play an important role to obtain valid data, but also to derive an optimum of information. As a fundamental requirement, detailed theoretical and model-based approaches to data analysis need to provide a solid basis to establish data precision and accuracy. Beyond this, innovative concepts may lead to unexpected insights into the specific performance of the main morphological components of hair (cuticle, cortex: intermediate filament & matrix) as well as their changes with cosmetic processes and products.