HARDNESS OF EMULSION LIPSTICKS 49 Table VI Heat of Transition of Endothermal Peak of Figure 5 Formula 1-1 1-2 1-3 Water content (parts by weight) 5 10 15 Heat of transition (J/g) 4.63 4.35 none 1, 2, and 3 of Table II) are shown in Figure 4. The emulsion lipsticks have a smaller peak area than a conventional lipstick. The heats of transition are given in Table V. The heats of transition of Formulae 2 and 3 are lower than that of Formula 1, which implies that waxes in emulsion lipsticks are less crystalline. The use of emulsion droplets appears to interfere with the crystallization of the waxes. Also, the crystallization (heat of transition) of Formula 3 is smaller than that of Formula 2. However, Formula 3 gives a greater hardness (Table II). This supports the view that crystallization is not the only factor that affects hardness. The effect of water content in emulsion lipstick formulae on the amount of crystalliza- tion was studied for Formulae 1-1, 1-2, and 1-3 of Table IV. The heat of transition calculated from Figure 5 is listed in Table VI. When the water content was changed from 5 to 10 parts by weight, the crystallization (heat of transition) decreased only slightly. However, the hardness of Formula 1-2 is about 1.6 times that of Formula 1-1 (Table IV), which is indirect evidence that the size and number of emulsion droplets are also very important factors for hardness. It seems likely that a larger number of emulsion droplets will cause the hardness of the lipsticks to be higher. When the water content is 15 parts by weight, the endothermal peak disappears, i.e., there is no crystallization in Formula 1-3. But the hardness of Formula 1-3 is the highest among these three samples. Thus the effect of emulsion droplets on the hardness is very important for emulsion lipsticks, irrespective of crystallization of waxes. ACKNOWLEDGMENT The authors would like to thank Dr. A N. Gent of the University of Akron for his helpful discussion. REFERENCES (1) I. Iida, Recent trend of development of lipsticks viewed from the point of touch and make-up effect, FragranceJ., 20, 22-28 (1992). (2) N. Sato, Lipcolor composition, Eur. Pat. App/. EP 585,981 (1994). (3) G. Schneider, S. Teichmann, M. Klier, and M. Aul, Cosmetic sticks containing beeswax and wax esters for prevention of chapped lips, Ger. Often. DE 4,306,068 (1994). (4) M. Fujii, Development of DGS (isopalmityl diglyceryl sebacate) as a vehicle component of lipsticks for the purpose of protecting lips from dryness, FragranceJ., 22, 31-37 (1994). (5) M. Mamyama, Characteristic hardness and gloss of natural waxes, FragranceJ., 18, 52-58 (1990). (6) A. Harashima, Functions of silicones and their application to lipsticks, FragranceJ., 20, 50-56 (1992). (7) D. G. Krzysik, Cosmetic lipsticks containing alkylmethyl siloxanes, U.S. Pat. US 5,288,482 (1994).

50 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (8) A. Kojuma, Y. Endo, J. Tsujumura, and T. Kizu, Cosmetic makeup pastes containing volatile oils, modified monotmorillonites, polar substances, and lipophilic surfactants,Japan KoKai Tokkyo KohoJP 01,106,809. (9) R. Leporati and L. Tigano, Solid water-in-oil emulsions for lip products, Cosmet. Toilerr., 108, 65-68 (1993). (10) M. Nakajuma and M. Osaki, Functions of lanolin and its derivatives and their application to lipsticks, FragranceJ., 20, 3649 (1992). (11) D. F. Williams and W. H. Schmitt, Eds., Chemistry and Technology of the Cosmetics and Toiletries Industry. (Chapman & Hall, Glasgow, 1992).