LIGHT SCATTERING THEORY TO MEASURE RINSABILITY OF HAIR CONDITIONERS 405 determine concentration based on optical density. This method can be applied to deter- mine the rinsability of various conditioner systems with varying chemistries. Future ex- periments will include studying more complex systems, commercial conditioners, 2-in-1s and shampoo systems. In addition, whole-head salon studies will be conducted in the hopes of correlating the instrumental rinsing data to consumer perceivable data. Last, continued development includes plans to correlate wet frictional data to the rinsing data. ACKNOWLEDGMENTS The authors would like to thank the Croda R&D team and Research Director Mr. Abel Pereira for their contribution and continued support on this project. REFERENCES (1) Olivares, Ernesto. “Desalination: A Global Solution to Water Scarcity.” Visual.ly, Energy Recovery, 7 July 2013, accessed March 7, 2018 visual.ly/community/infographic/environment/desalination-global-solution- water-scarcity. (2) “Water Facts.” UN-Water, WHO/UNICEF, accessed March 7, 2018 www.unwater.org/water-facts/. (3) M . C. Robles, Marketing required for water effi cient products to succeed in beauty and personal care, Euromonitor International Blog, Euromonitor International, accessed February 15, 2018, blog. euromonitor.com/2016/05/marketing-required-for-water-effi cient-products-to-succeed-in-beauty-and- personal-care.html. (4) R. Savo et al., When the structure becomes insignifi cant: invariance of the mean path length in light- scattering media, Advanced Photonics 2018, BGPP, IPR, NP, NOMA, Sensors, Networks, SPPCom, SOF, 2018, https://doi.org/10.1364/NOMA.2018.NoM3D.5 (5) C . P. Lienemann et al., Optimal preparation of water samples for the examination of colloidal material by transmission electron microscopy, Aquat. Microb. Ecol., 14, 205–213 (1998). (6) B. C. Matlock et al., Analyzing differences in bacterial optical density measurements between spectro- photometers, ThermoFisher Scientifi c, UV-Vis/Fluor-Molecular Spectroscopy, Wilmington, DE, assets. thermofi sher.com/TFS-Assets/CAD/posters/nanodroptryPOSTER.pdf., 2011 (7) Bru, P., et al. “Particle Size and Rapid Stability Analyses of Concentrated Dispersions: Use of Multiple Light Scattering Technique.” ACS Symposium Series Particle Sizing and Characterization, vol. 881, 25 June 2004, pp. 45–60. ACS Symposium, doi:10.1021/bk-2004-0881.ch003.