EXTRUSION OF COSMETIC PRODUCTS 901 Figure 11. I I The extrusion pressure of a wax system as a function of the concentration of carnauba wax and mineral oil in a nonthixotropic system It is frequently desirable to have effects similar to those of cocoa butter where the melting point is not affected, but the release, or other properties, can be changed. However, the addition of triglycerides, such as cocoa butter or cocoa butter substitute, can lead to other problems. It is well known that triglycerides can exist in various polymorphic forms that is, they have various crystal structures designated a, •', and •. The a form is the most unstable and rapidly converts to the •' form. The •' form slowly converts to the most stable • structure. During the change from a to •, the triglyceride has a certain mobility within the wax system and frequently will deposit on the outer surface of the lead. This is commonly called bloom and has plagued the chocolate industry for a number of years. Bloom was intentionally grown on the surface of a cosmetic lead for investigation. This matehal was carefully scraped off the lead and examined by IR. Figure 8 compares the original tri- glyceride of the formulation to the scrapings.

902 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table I Effect of Pigment on the Breaking Strength and Extrusion Pressure of Cosmetic Leads Breaking Strength Extrusion Pressure Pigment (era) (psi) Black (carbon black) Black (iron oxide) Brown (iron oxide) Red (iron oxide) Yellow (iron oxide) Green (chromium oxide anhydrous) Green (chromium oxide hydrated) Blue (ferric ferro cyanide) 22.50 1100 13.00 350 10.80 300 9.00 175 10.00 250 9.00 175 10.00 200 14.00 300 Table II Effect of the Addition of Wax on the Extrusion Pressure of a Standard Wax Base Extrusion Pressure (psi) Wax Added (%) 0 5 10 15 20 Carnauba 900 1100 1150 1200 1225 Ceresine 900 950 1025 1100 1150 Cocoa butter 900 850 700 625 550 The control of bloom is usually accomplished by the substitution of matehals, such as Eutectol©, * which have only one crystal form. If this is not feasible, a controlled-temperature process known as temper- ing is employed. This step in the manufacturing process involves the controlled cooling of the wax mixture so that the stable fi form is en- couraged. The use of surfactants has also been shown to inhibit bloom (4). PIGMENT EFFECTS The pigments employed to attain the various shades required in eyebrow and lipliner pencils can also affect the strength of the resulting product. It is frequently necessary to have completely different wax bases for various pigments. The effect of adding various pigments to a wax base on the pressure required for extrusion and the breaking strength of lead is shown in Table I. * A&S Corporation, 10 Summit Rd., Verona, N.J.