JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 14. Typical sag test. This paste has a sag number of 5.

CHARACTERIZATION OF DENTIFRICES 203 span of time taken to reach a given sag number in five successive trials on one paste. CONCLUSIONS The measurement and control of the complex and rather ill-defined rheological properties of semisolids are becoming increasingly important to industry and to the consumer to-day. It is hoped that the methods des- cribed will prove useful in factories and in other laboratories for research, development and quality control. In the absence of expensive, multipurpose equipment, adequate measurements may still be made with rather simple devices. This work has been based on the research of scientists from the United Kingdom, South Africa, Israel and the United States on materials as diverse as cooking fats, butter, Napalm and paints. ACKNOWLEDGMENT I wish to thank Mr J. A. Cristofides for his assistance during an indus- trial training period. (Received: 5th September 1973) REFERENCES (l) Sargent, J. D. The measurement of 'body' in butter by physical determination. N.Z.J. Sci. Technol. 16 213 (1935). (2) Soltoft, T. On the consistency of hardened fats. Proc. Int. Congr. Rheol. 2nd 273 (1949). (3) Sherman, P. Industrial Rheology 194 (1970) (Academic Press, London and New York). (4) Clardy, L. et al. A shortening consistometer. J. Amet,. Oil. Chem. Soc. 29 591 (1952). (5) Brown, W. S. and Cutler, I. B. Extrusion of soft solids through a tube, J. Colloid. $ci. 12 195 (1957). (6) Owen, V. J. and Worrall, W. E. An extrusion method for the testing of the flow properties of plastic clays. Tt,ans. Brit. Ceram. Soc. 8 285 (1960). (7) British Standard 3712, Part 1 (1964). (8) Hawkins, A. E. Non-Newtonian technology associated with some food products. Chem. Eng. (London) Jan. 19 (1971). (9) Prentice, J. H. The rheology of margarine and compound cooking fat I. Brit. Fd. Mfg. Ind. Res. Ass. Res. Rep. No. 37 (1952). (10) Prentice, J. H. An instrument for estimating the spreadability of butter. Lab. Pt'act. 3 186 (1954).