Using Interfacial Rheology to Investigate a Soap & Surfactant based Body Wash

Carole Moules
Camtel Ltd., 5 Carrington House, 37 Upper King Street , Royston, Herts SG8 9AZ , UK

INTRODUCTION： Two samples of commercial body wash were presented for testing. Solution BW-1 is a natural soap based system and Solution BW-2 is a commercial surfactant based system. Three further samples of potassium laurate (KL), a commercial surfactant (CS) and a mixture of KL and CS in the ratio 30:70 were also provided. BW-1 is known to contain both lauric and myristic acid in its formulation. Visually the customer observed that BW-1 formed a rigid film with excellent foam stability whereas BW-2 formed a quite mobile film with significantly less foam stability. The three surfactant solutions showed no rigidity. The customer was looking for a method to distinguish body wash products based on their formulation. Bulk rheology and surface tension values were very similar for BW-1 and BW-2.