Time dependent scattering properties of slow decaying liquid foams

An experimental procedure is described to explore the physical characteristics of foam structures using a diagnostics tool based on elliptically polarized light scattering (EPLS) concept. The experimental system was constrained in cylindrical geometry and used to test a slow decaying, stable foam. Measurements were taken over a period of 30 h to utilize the scaling behavior of foam over long time scales. The normalized Mueller matrix elements were obtained for backscattering angles in the range of 120-150°. Additionally, Monte Carlo simulations were conducted and compared to the experiments. Experimental results suggest that backscattering signals, as quantified with the matrix elements (S₁₁, S₁₂, and S₃₃), are sensitive to foam age and show a dynamic range especially at angles between 120° and 135°. The Monte Carlo simulations display a qualitative agreement with the angular profiles obtained from experiments. The age dependence of the properties of shaving foam in terms of the liquid fraction, bubble size, and polydispersity is used to understand the correlation with the measured profiles of S₁₁, S₁₂, and S₃₃.