898 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 30- & 21 • 15 5 10 15 20 25 % Cocoa Butter Figure 7. Breaking strength as a function of cocoa butter concentration Cosmetic leads are formulated principally from waxes, fats, and oils. The characteristics of these waxes and combination of the waxes can be found in the works of Bennett (3). Beeswax, carnauba, and ceresinc are used primarily for body and strength in the stick. Lanolin, mineral oil, and cocoa butter are good emollients. Japan wax is used because it has certain qualities that improve the sharpening of cosmetic leads. Micro- crystalline wax, carnauba wax, and mineral oil add thixotropic properties to the product. Various blends of these component waxes could give products with qualities of lipsticks and/or cosmetic leads. A typical formulation for cosmetic lead could be the following: Japan wax .......................... 25% Beeswax ............................ 15 Ceresinc ............................. Carnauba ............................ 6 Mineral oil ........................... 3 Lanolin ............................. 20 Cocoa butter ........................ 10 Pigment ............................ 17 A lead of various hardness could be formed by changing the ratio of the lower-melting waxes to the higher-melting waxes.

EXTRUSION OF COSMETIC PRODUCTS 899 I I I I I 4 8 I I ! I I Wavelength, (microns) Figure 8. IR spectra of triglycerides [ 25 •, 20 Q• ,• 15 • 1o • 5 Figure 9. 500 1000 1500 Pressure, (psi) Break{ng strength as a function of extrus{on pressure PHYSICAL PROPERTIES The characteristics most sought after in stick formulations are the strength of the stick and the release properties of the product. These relationships can sometimes be equated to the penetration of the wax base and its melting point. Figure $ shows the relationship of melting point to penetration of the cosmetic lead formulation previously discussed. This relationship is only applicable to this particular system. It has also been found that