TECHNIQUES OF FOAM MEASUREMENT 401 present, which is not really a foam, or foams with very large bubbles, which are not encountered in shampoo practice. GRAPH 4 PLOT OF SPECIFIC SURFACE V/S AGEOF FOAM IN MINUTES 2 M H N C Time minutes 1 4 8 1 4 8 1 4 8 1 4 8 « 0.40 -- -- 0.85 -- -- 1-12 -- -- 1-15 -- -- 1 1.05 0.30 0.27 1.77 0.52 0.37 1-88 1.18 0.40 1.95 0.42 0.40 1« 1.36 -- -- 2-08 -- -- 2.10 -- -- 2.25 -- -- 2 1.51 0.68 0.60 2.28 1.00 0.87 2.17 1.62 0.88 2-40 0.95 0.85 2• -- __ __ 2.37 -- __ 2.25 __ __ 2.42 __ __ 3 1.70 0.86 0.88 2.42 1.27 1.20 2.30 1.78 1.10 2.50 1.20 1.02 4 1.76 1.04 1-05 2.48 1.48 1-37 2.38 1.88 1.35 2.55 1.35 1,18 5 1.81 1.12 1.22 2.55 1.58 1.50 2-40 1.98 1.45 2.60 1.48 1.30 6 1.86 1-22 1.30 2.58 1.68 1.60 2.43 2.05 1.55 2.65 1.52 1.38 8 -- 1-31 1.38 -- 1.78 1.72 -- 2.15 1.68 -- 1.68 1.48 10 -- 1.39 1.48 -- 1-85 1.78 -- 2.20 1.75 -- 1.75 1.62 70 • • I • AGE OF FOAM IN UlNUTE5 The rate of draining of the four shampoo detergent solutions was studied after 1, 4 and 8 minutes. All the 1 minute samples drained after 6 minutes, as is shown in Table 2. Table 2 Draining of Mother Liquor from Shampoo Foam.

409, JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS M drains more slowly than the other three. This is to be expected if we consider the ease of foaming and the larger volumes of foam produced per cc of detergent solution. The draining rate of the other three shampoo detergent solutions is similar, although N is quicker draining foam than HorC. An experiment was carried out to investigate the foam volume and viscosity of soiled shampoo detergent solutions. Carefully blended salon sweepings were washed in the shampoo detergent solution, the soiled detergent solution was squeezed out and foams generated from these detergent solutions. The foam volume and the viscosity differential of the foam was measured. The viscosity of the soiled detergent solution is given in Graph $. The characteristic of the N foam altered, the super foam curve disappearing altogether, and the detergent appeared exhausted. M and H altered their characteristics very little. There is a slight increase in viscosity with both, but the detergent solution is not exhausted, and the presence of dirt did not seem to make too much difference to the foam. There is a very great increase in viscosity with C. The specific volume of the soiled shampoo detergent solution with M, H and N are the same as with the unsoiled samples. There is a small increase in specific volume with C, the soiled solution generation 16.3 ml of foam/g of solution, and the unsoiled sample generating 19.3 ml of foam/g of solution, after 4 minutes' beating at 720 r.p.m. It is clear that the soil has a profound effect on the foam viscosity, and this must be important in the differences in the first and second applications of a shampoo. 2. Toothpaste There is very little difference between the specific volume obtained from the shampoo detergent and toothpaste solutions studied. This is surprising as the concentration of active detergent in the toothpaste solutions we have used is only 0-30//0, compared with 1.5% with the shampoo detergents. Both the concentrations are similar to those used in practice. Thus the volume of foam obtained from shampoos is very much less per unit weight of detergent than from toothpastes. Other components of the toothpaste must be responsible for this increase of foam volume. PD/1 and PD/2 produce the same volume of foam and are in practice the highest foamers among the toothpastes studied (25 cc of foam/g of slurry beaten at 720 r.p.m.). CD is slightly lower at 22 cc of foam/g of slurry. CS does not produce foam at the 15ø//o w/w 25% is the lowest concentration at which a stable foam is produced. This foam is a creamy foam and yields 5 cc of foam/g of slurry after 4 minutes' beating at