Table V Spreadability of Each Solvent INCI name Peak positive (fi rmness) Positive area (hardness work done) Peak negative (stickiness) Negative area (adhesiveness) g g.sec g g.sec 1 Isododecane 8.5 ± 0.3 0.1 ± 0.0 -10.5 ± 0.5 -0.0 ± 0.1 2 Cyclotetrasiloxane and cyclopentasiloxane 9.1 ± 0.1 7.7 ± 0.2 -9.7 ± 0.1 -0.0 ± 0.0 3 Olea europaea (olive) fruit oil 11.8 ± 0.2 8.4 ± 0.2 -9.4 ± 0.6 -0.1 ± 0.0 4 C12-15 alkyl benzoate 15.0 ± 0.1 9.0 ± 0.2 -11.2 ± 0.0 -1.3 ± 0.0 5 Shea butter ethyl esters 10.6 ± 0.1 7.7 ± 0.3 -9.4 ± 0.2 -0.1 ± 0.0 6 Mineral oil 62.1 ± 0.7 20.1 ± 0.1 -55.6 ± 0.8 -8.1 ± 0.1 7 Helianthus annuus (sunfl ower) seed oil 46.1 ± 0.2 15.8 ± 0.5 -37.7 ± 0.3 -5.1 ± 0.0 8 Isopropyl isostearate 12.3 ± 0.1 8.3 ± 0.2 -10.6 ± 0.4 -0.1 ± 0.0 9 Dimethicone 10.4 ± 0.4 7.3 ± 0.6 -9.9 ± 0.3 -0.1 ± 0.0 10 Heptyl undecylenate 9.2 ± 0.1 7.2 ± 0.1 -9.0 ± 0.3 4.7 ± 3.4 11 Isopropyl myristate 9.7 ± 0.1 7.2 ± 0.5 -10.4 ± 0.8 -0.1 ± 0.0 12 Caprylic/capric triglyceride 21.4 ± 0.1 10.3 ± 0.4 -15.1 ± 0.1 -1.9 ± 0.0 13 Ethanol 8.9 ± 0.1 0.1 ± 0.0 -9.3 ± 0.3 -0.0 ± 0.0 14 Ricinus communis (castor) oil 477.5 ± 4.8 107.5 ± 1.5 -484.1 ± 3.2 -57.6 ± 0.4 15 Propanediol dicaprylate/caprate 13.5 ± 0.1 8.9 ± 0.3 -10.7 ± 0.1 -0.1 ± 0.0 16 2-Ethylhexyl palmitate 13.6 ± 0.1 8.3 ± 0.1 -11.2 ± 0.3 -1.1 ± 0.0 17 Diethylhexyl 2,6-naphthalate 238.0 ± 3.6 62.7 ± 0.5 -224.8 ± 18.2 -30.5 ± 0.5 18 Pentylene glycol 27.3 ± 0.1 11.8 ± 0.1 -21.4 ± 0.1 -2.7 ± 0.1 19 PPG-3 benzyl ether ethylhexanoate 16.0 ± 0.1 9.3 ± 0.7 -11.5 ± 0.0 -1.2 ± 0.0 20 Tris(PPG-3 benzyl ether) citrate 278.0 ± 6.3 71.9 ± 0.9 -277.1 ± 6.4 -35.6 ± 1.1 21 Butyloctyl salicylate 17.3 ± 0.2 10.0 ± 0.4 -12.3 ± 0.2 -1.5 ± 0.0 22 Diisopropyl adipate 10.0 ± 0.1 8.3 ± 0.3 -9.5 ± 0.2 -0.1 ± 0.0 23 Ethylhexyl methoxycrylene 3,837.4 ± 35.8 1,273.8 ± 12.5 -3,765.4 ± 42.8 -768.5 ± 13.7 24 Polyester-8 3,252.8 ± 37.5 1,040.5 ± 14.7 -3,238.9 ± 43.4 -640.0 ± 15.3 SOLVENT EFFECTS ON SPF AND BROAD-SPECTRUM PROTECTION 163

JOURNAL OF COSMETIC SCIENCE 164 structural elements, including ester bonds, conjugated structure, and aromatic ring(s). Ethylhexyl methoxycrylene and polyester-8 also had –CN groups. These four solvents had an inherent SPF-absorbing capacity as well, which led to the high SPF of the UV fi lter–solvent mixtures. Our results indicated that these structural characteristics are important and can in- dicate good performance however, the absence of some of these structural elements did not necessarily prevent a solvent from being a booster. Multiple solvents caused a signifi cant hyp- sochromic or bathochromic shift in the UV fi lters’ λmax, especially for butyl methoxydibenzo- ylmethane. However, in all cases, the λmax stayed in the range where the UV fi lter was normally absorbed in. In the case of the UVB fi lters, most solvents only caused a minimal or no shift. Although polyester-8 and ethylhexyl methoxycrylene achieved the highest SPF values, they were viscous and sticky and had a strong color. Optimizing their use level is recommended to achieve good performance and acceptable aesthetics. For a formulator t o select and estimate the effect of a solvent on the UV-absorbing char- acteristics of a UV fi lter, solubility of the UV fi lter in the solvent, chemical structure, and mechanism of action of the solvent and solvent–UV fi lter interactions should be consid- ered. Results of this study provide practical information that can guide sunscreen formu- lators in selecting solvents for UV fi lters and making more effective sunscreens. ACKNOWLEDGMENTS We would like to e xpress our thanks to the suppliers, including Symrise, Croda, BASF, East- man, Active Concepts, Innospec, AAK, Lubrizol, INOLEX, Hallstar, and Wacker Chemie for providing us with samples of their ingredients. We also acknowledge the assistance of Katie Wolf, Jess Kona-Stanciu, and Janelle Barth in this project. We acknowledge the partial sup- port from Access Business Group International LLC under award number N-127059-01. REFERENCES (1) H. H önigsmann, E rythema and pigmentation, Photodermatol. Photoimmunol. Photomed., 18, 75–81 (2002). (2) J. H. Rabe, A. J . Mamelak, P. J. McElgunn, W. L. Morison, and D. N. Sauder, Photoaging: mechanisms and repair, J. Am. Acad. Dermatol., 55, 1–19 (2006). (3) Hawaii State Senate, A bill for an act relating to water pollution, 29th Legislature SB 2571, 2018, ac- cessed December 4, 2019, https://www.capitol.hawaii.gov/session2018/bills/SB2571_.HTM. (4) City of Key West, FL City Commission, Action Minutes—Final, 2019, accessed December 4, 2019, http://keywestcity.granicus.com/MediaPlayer.php?view_id=1&clip_id=941. (5) Committee on Government Operations, Consumers, and Veterans Affair, Thirty-Third Legislature of the Virgin Islands, 2019, accessed December 4, 2019, http://legvi.org/committeemeetings/Rules%20 and%20Judiciary/Thursday,%20June%2013,%202019/Bills/33-0043.pdf (6) S. L. Schneider a nd H. W. Lim, Review of environmental effects of oxybenzone and other sunscreen ac- tive ingredients, J. Am. Acad. Dermatol., 80, 266–271 (2019). (7) S. Q. Wang and H . W. Lim, Principles and Practice of Photoprotection (Springer International Publish- ing, Cham, Switzerland, 2016). (8) S. Abbott, Solubi lity Science: Principles and Practice (Creative Commons BY-ND, Attribution and No- Derivatives, 2018), https://www.stevenabbott.co.uk/_downloads/Solubility%20Science%20Principles%20 and%20Practice.pdf. (9) J. Wiechers and S . J. Abbott, Formulating for Effi cacy, the Software, 2011/2013, accessed August 24, 2019, https://www.jwsolutionssoftware.com/. (10) M. A. Kalam, S. Alsheri, A. Alshamsan, M. Alkholief, R. Ali, and F. Shakeel, Solubility measurement, Hansen solubility parameters and solution thermodynamics of gemfi brozil in different pharmaceutically used solvents, Drug Dev. Ind. Pharm., 45, 1258–1264 (2019).