PRACTICAL ASPECTS OF EMULSION FORMULATION* By I.'R. HOLLENBERG I/an Dyk & Company, Inc., Belleville, N.y. I'r IS THE PURPOSE Of this paper to indicate briefly a practical approach to the subject of cosmetic emulsion technology. In general, emulsions may be said to consist of a dispersion of ex- ceedingly small droplets of a liquid in another equally immiscible liquid. The term oil-in-water emulsion is, therefore, applied to those emulsions in which oil is dispersed in an aque- ous medium. Conversely, where water is the dispersed liquid, the resulting suspension is classified as a water-in-oil emulsion. Most cos- metic emulsions fall into the former category they include vanishing creams, cleansing creams, cold creams, skin and hand lotions, de- odorant creams, etc. The so-called tissue, or'nourishing, creams are, as a rule, however, water-in-oil emul- sions. Emulsions may further be classified into the liquid or solid type. The solid emulsions are formed by oils or fats that are liquid when heated but which solidify when cooled to room temperature. Another means of differentiating * Presented at the May 20, 1949, Meeting, New York City. emulsions other than by phase clas- sification or consistency is in terms of function. We use the terms "non-vehicle" and "vehicle." Per- haps the simplest way to 'define these types is by illustration. Al- though the terminology is admit- tedly somewhat cumbersome, it is believed that the meaning will be- come clear. The vehicle type emul- sion may be described as an emul- sion which in itself does not exert a cosmetic effect, but acts as a carrier for the cosmetic agent. As .an ex- ample, we may cite suntan, de- odorant, and make-up creams. In these preparations, the emulsion is merely used as a vehicle for the as- tringent in the deodorant cream, the ultra-violet absorbent in the suntan cream, or the pigments in the make- up preparation. The non-vehicle type may be characterized as an emulsion whose basic ingredients-- fats, oils, water, etc.--give the de- sired cosmetic effect. Among the non-vehicle preparations are cold or cleansing creams, hand lotions, night creams, etc. For example, ill a cold cream the evaporation of the water phase on the skin surface 368

PRACTICAL ASPECTS OF EMULSION FORMULATION 369 gives the characteristic cooling ef- fect. The ingredients of the oil phase afford the desired cleansing, lubricating, and emollient effects. The non-vehicle type emulsion is comparatively easy to formulate and does not present the problems characteristic of the vehicle type. placed in a jacketed vessel and heated and stirred to around 75- 80øC., until melted. They are then stirred into another similar vessel containing a solution of the aqueous ingredients, which have been heated in a like manner, usually at a tem- perature that is about 5 ø higher. Figure 1.--Non-Vehicle Type Creams 7 ¸ A 29 1 55 B 35 1 5O C 55 .. 20 A 65 2 .. B 67 2 c ss • '• A 40 .. 25 B 40 27 C 55 '1' 5 A 88 1 1 B 90 1 .. C 94 .... Cold or Cleansing Creams 15 .. •o i' 'i' Vanishing Creams 25 .. 20 T 'i "• .. 2 .. i6 2s Tissue or Night Creams 3 10 10 .. 3 .. 25 2 .. •o • 8 5 'f 2 .. .. 7 Cream Lotions 3 1 1 .. 5 2 .. 'i " • s i .... 'i .. 1'.• 2.5 In Fig. 1 are listed a dozen in- gredients which are commonly used in the non-vehicle creams. It will be noted that these formulations have a good deal in com/m3n,mot., only as far as ingre&{eht•m•'½'Sn- cerned, but also in e. he,metqhod•l•f• manufacture.., of tiss•, Stirring is continued, rather rapidly, until the temperature drops to around 3040 ø . Solid creams may be perfumed and packaged at this temperature. Liquid creams, on the other hand, are stirred until completely cooled. The general procedure for prepar- i•hg water-in-oil emulsions is some- •hat as follows. The fatty materi- 4• ,•ir• stirred and heated together im:a•jacketed vessel until melted,