Formula code Casson yield stress (Pa) Flow index Consistency index (Pa·s) n Shear stress at the limit of LVE (Pa) Storage modulus at the limit of LVE (Pa)of Loss modulus at the limit LVE (Pa) Damping factor Flow point (PA) Viscosity at different shear rate values (Pa·s) 25·s-1 75·s-1 Infi nite shear viscosity K7.5B 7.5 G – – – 50.7 ± 17 8.3E+04 ± 1.6E+04 2.2E+04 ± 0.4E+04 0.26 ± 0.00 123.0 ± 14.0 56.0 ± 1.1 9. ± 1.4 – K5B5 567.5 (0.99) 0.42 (0.95) 236.8 (0.95) 206.0 ± 72 3.1E+05 ± 0.62E+05 7.5E+04 ± 1.9E+04 0.24 ± 0.02 410.3 ± 60.1 43.0 ± 2.9 24 ± 8.2 13.5 ± (0.99) N 0.05 G 713.2 (0.98) 0.26 (0.98) 395.5 (0.98) 101.6 ± 41.7 1.1E+05 ± 0.58E+05 2.8E+04 ± 1.4E+04 0.27 ± 0.02 246.3 ± 58.8 44.0 ± 7.9 13 ± 0.25 6.16 ± (0.98) K10BG2 – 0.07 (1.0) 604.8 (1.0) 93.9 ± 28.4 1.4E+05 ± 0.15E+05 3.3E+04 ± 0.14E+04 0.24 ± 0.04 153.0 ± 15.6 59.0 ± 0.9 11 ± 4.7 – a K = kaolin, B = bentonite, N = Natrosol250 ® HHX, G = glycerin, over-the-shelf mud = RV, NC, BL, BS, and AQ. Results represent the mean ± SD or mean (2) for parameters calculated using Casson and Herschel–Bulkley models (n = 3). For samples RV, NC, K15G, K7.5B7.5G, and K10B2G the models are not applicable to data, results make no sense rheologically. Table III Continued JOURNAL OF COSMETIC SCIENCE 346

PHYSICAL PROPERTIES AND STABILITY OF DEAD SEA MUD MASKS 347 However, when our data were fi tted to the Herschel–Bulkley model, we faced a problem of meaningless negative yield stress values for many of the samples, which include AQ, BL, BS, NC, K15G, K7.5B7.5G, K5B5, N0.05G, and K10B2G. Figure 3. Typical shapes of Casson and Herschel–Bulkley (HB) modeled fl ow curves, data shown are for B10G at initial time (fi rst day) point compared with unmodeled fl ow of the same formulation sample. Figure 4. Casson and Herschel–Bulkley (HB) modeled fl ow curves for K7.5B7.5G at initial time point com- pared with observed fl ow curves of the same formulation.