FIXED AND BULK EMULSION WATER 57 (12) Deutscher Arzneimittel-Codex (DAC), Erganzungsbuch zum Arzneibuch, (Govi-Verlag, Frankfurt/ Main, 1979). (13) H. Tronnier, •lber die 1Virkungsweise indifferenter Salben und Emulsions-systeme an der Haut in Abhangigkeit yon ihrer Zusammensetzung, (Editio Cantor, Aulendorf/W•irtt, 1964). (14) W. Heering, Die Struktur des Gelger?•sts der 1Vasserhaltigen Hydrophilen Salbe DAB 8 Anwendung der Gefrierbruch-Atztechnik und Transmissionselektronenmikroskopie auf kolloide pharmazeutische Zubereitungen, thesis Braunschweig (1984).

j. $oc. Cosmet. Chem., 35, 59-71 (January/February 1984) Measuring the viscoelastic properties of aerosol shaving foams M. M. BREUER and H-C. TSAI, The Gillette Company, Personal Care Division, Gillette Park, Boston, Massachusetts 02106. Received July 22, 1983. Presented at the 57th Colloid and Surface Science Symposium, Toronto, Canada, June, 1983. Synopsis A method has been developed for measuring the theological properties of rigid aerosol foams using the Instron Tester. The force, acting on a glass plunger during its gradual penetration into a glass cup filled with aerosol foam, was measured in three modes of operation: a) slow plunger penetration to very small depths giving quasi-static force-displacement curves and the elastic moduli of foams b) single penetration mode to larger depth at faster speeds yielding foam viscosity as functions of shear rates and the yield points of foams and c) dynamic, oscillating plunger movements allowing the calculation of the dynamic storage and loss moduli of the foams. An interpretation of the data in terms of theological models has also been developed. INTRODUCTION The acceptability of many consumer products is closely linked to the quality and texture of the foam they produce (e.g., shaving foams and creams, shampoos, etc.). These attributes depend, to a large measure, on the rheological properties of the foams. Only limited experimental and theoretical work has been done on the theology of foams. The early work has been reviewed by Bikermann (1) who described the principal techniques then available for measuring foam theology. Most of these methods had been developed originally for the characterization of emulsions and colloidal disper- sions (2) and were later adapted for the study of foams. Sanders (3) described the use of a simple penetrometer which measured foam stiffness for empirical evaluation and quality control. More recently, Cottie (4) designed a torsional foam viscometer for the determination of fire-fighting foam viscosities. Sharovarnikov and Kokorev (5) developed an elegant technique that determines the longitudinal viscoelasticity of a foam column immediately after its extrusion from a pipe. Komatsu and Yamada (6,7) described a parallel plate viscometer especially designed for the measurement of the viscoelasticity of light foams produced by cosmetic products (e.g., shampoos). In the present paper, we describe the development of an experimental technique that is suitable for determining the viscoelastic properties of rigid foams (e.g., shaving foams that are capable of retaining their shape for considerable lengths of time in the absence of extraneous forces). To date, the only published method available for measuring the 59