545 CHARACTERIZATION OF BLEACHED HAIR phases of the hair. When conditioned in dry ambient environments, cysteic acid moieties in keratin appear to bond ionically with proteinaceous residues, where the resultant physical cross-links within the fiber matrix are quite strong. Hence, many moderate-humidity thermomechanical measurements may not straightforwardly distinguish the effects of oxidative physiochemical fiber damage. However, in the wet state, water solvates hydrogen and ionic physical cross-links within the cortex and the residual thermomechanical strength is bestowed to the durability of the remaining disulfide bonds. Consequently, results from wet thermal and wet mechanical testing protocols accurately describe oxidative chemical damage however, in the dry state, the effects of cystine oxidation may not directly correlate with results from routine mechanical testing. ACKNOWLEDGMENTS The authors would like to acknowledge Dr. Guojin Zhang for the virtual ISys lessons T-bone Schiess, William Thompson, and Fan Wu of Ashland LLC and Geddy Lee of Rush. Special thanks to Dr. Crisan Popescu for any results that we properly interpreted. REFERENCES (1) C. R. Robbins, Chemical and Physical Behavior of Human Hair, 4th Ed. (Springer-Verlag, New York, 2002), pp. 360–435. (2) E. P. Everaert, S. Zhang, D. Tran, B. Kroon, G. Zhang, W. T. Thompson, and R. L. McMullen, 2015. Strengthening the hair fiber from within: repairing the cortex of damaged hair, Zurich, Switzerland, 21–23 Sept 2015. 23rd IFSCC Conference accessed April 1, 2021, http://tst.pg2.at/abstracts/data/full_ papers/full_paper_90.pdf. (3) L. J. Wolfram, K. Hall, and I. Hui, The mechanism of hair bleaching, J. Soc. Cosmet. Chem., 21, 875–900 (1970). (4) A. J. Grosvenor, S. Deb-Choudhury, P. G. Middlewood, A. Thomas, E. Lee, J. A. Vernon, J. L. Woods, C. Taylor, F. I. Bell, and S. Clerens, The physical and chemical disruption of human hair after bleaching— studies by transmission electron microscopy and redox proteomics, Int. J. Cosmet. Sci., 40, 536–548 (2018). (5) W. W. Edman and M. E. Marti, Properties of peroxide-bleached hair, J. Cosmet. Sci., 12, 133–145 (1961). (6) C. Popescu (June 16, 2016), The internal structure of hair and its interpretation by tensile strength and DSC measurements, The Cosmetic Chemist, accessed March 13, 2021, http://www.thecosmeticchemist.com/ education/hair_care_technology/the_internal_structure_of_hair.html. (7) C. Popescu and C. Gummer, DSC of human hair: a tool for claim support or incorrect data analysis, Int. J. Cosmet. Sci., 38, 433–439 (2016). (8) D. Istrate, C. Popescu, and M. Möller, Non-isothermal kinetics of hard alpha-keratin thermal denaturation, Macromol. Biosci., 9, 805–812 (2009). (9) F.-J. Wortmann, C. Popescu, and G. Sendelbach, Non-isothermal denaturation kinetics of human hair and the effects of oxidation, Biopolymers, 83, 630–635 (2006). (10) F.-J. Wortmann, G. Sendelbach, and C. Popescu, Fundamental DSC investigations of alpha-keratinous materials as basis for the interpretation of specific effects of chemical, cosmetic treatments on human hair, J. Cosmet. Sci., 58, 311–317 (2007). (11) F.-J. Wortmann, C. Springob, and G. Sendelbach, Investigations of cosmetically treated human hair by differential scanning calorimetry in water, J. Cosmet. Sci., 53, 219–228 (2002). (12) F.-J. Wortmann and H. Deutz, Characterizing keratins using high-pressure differential scanning calorimetry (HPDSC), J. Appl. Polym. Sci., 48, 137–150 (1993). (13) D. Istrate, “Heat induced denaturation of fibrous hard alpha-keratins and their reaction with various chemical reagents.” PhD thesis, RWTH Aachen. 2011. (14) F.-J. Wortmann, G. Wortmann, J. Marsh, and K. Meinert, Thermal denaturation and structural changes of alpha-helical proteins in keratins, J. Struct. Biol., 177, 553–560 (2012). (15) F.-J. Wortmann, A. Hullman, and C. Popescu, Water management of human hair, Int. J. Cosmet. Sci., 30, 388–389 (2008).

546 JOURNAL OF COSMETIC SCIENCE (16) G. Zhang, R. L. McMullen, R. Mendelsohn, and O. Musa, “Applications of Vibrational Spectroscopic Imaging in Personal Care Studies,” in Computational Optical Biomedical Spectroscopy and Imaging, S. M. Musa. Ed. (CRC Press, New York, 2015), pp. 1–26. (17) A. Kuzuhara, Analysis of structural change in keratin fibers resulting from chemical treatments using Raman spectroscopy, Biopolymers, 77, 335–344 (2005). (18) P. D. Pudney, E. Y. Bonnist, K. J. Mutch, R. Nicholls, H. Rieley, and S. Stanfield, Confocal Raman spectroscopy of whole hairs, Applied Spectroscopy, 67, 1408–1416 (2013). (19) V. Signori and D. M. Lewis, FTIR investigation of the damage produced on human hair by weathering and bleaching processes: implementation of different sampling techniques and data processing, Int. J. Cosmet. Sci., 19, 1–13 (1997). (20) A. Barth, Infrared spectroscopy of proteins, Biochim. Biophys. Acta., 1767, 1073–1101 (2007). (21) R. McMullen, D. Laura, S. Chen, D. Koelmel, G. Zhang, and T. Gillece, Determination of physicochemical properties of delipidized hair, J. Cosmet. Sci., 64, 355–370 (2013). (22) R. L. McMullen, S. Chen, and D. J. Moore, Spectrofluorescent characterization of changes in hair chemistry induced by environmental stresses, J. Cosmet. Sci., 62, 191–202 (2011). (23) R. L. McMullen and G. Zhang, Investigation of the internal structure of human hair with atomic force microscopy, J. Cosmet. Sci., 71, 117–131 (2020). (24) C. Barba, M. Martí, J. Carilla, A. M. Manich, and L. Coderch, Moisture sorption/desorption of protein fibres, Thermochim. Acta, 552, 70–76 (2013). (25) C. Robbins and C. J. Kelly, Amino acid analysis of cosmetically altered hair, J. Cosmet. Sci., 20, 555–564 (1969). (26) M .L. Tate, Y. K. Kamath, S. B. Ruetsch, and H.-D. Weigmann, Quantification and prevention of hair damage, J. Cosmet. Sci., 44, 347–371 (1993). (27) C. Popescu and E. Segal, Critical considerations on the methods for evaluating kinetic parameters from nonisothermal experiments, Int. J. Chem. Kinet., 30, 313–327 (1998). (28) T. Ozawa, Kinetic analysis of derivative curves in thermal analysis, J. Therm. Anal. Calorim., 2, 301–324 (1970). (29) D. Istrate, M. E. Rafik, C. Popescu, D. E. Demco, L. Tsarkova, and F.-J. Wortmann, Keratin made micro-tubes: the paradoxical thermal behavior of cortex and cuticle, Int. J. Biol. Macromol., 89, 592–598 (2016). (30) T. A. Evans, “Adsorption Properties of Hair,” in Practical Modern Hair Science, T. A. Evans and R. R. Wickett. Eds. (Allured Books, Carol Stream, IL, 2012), pp. 333–365.