Foam fraction as a function of gas velocity, at a liquid velocity of
0.205 cm/s, for a 0.06% wt. SDS + 1.0% wt. 1-Butanol solution, without
particles (red, solid circles) and, with 10% volume fraction of solids
(From STIM-LAB, 
= 2.65 g/cc,
mean size = 600-850 µm); uncoated or hydrophilic sand (blue, open
circles) and resin coated or hydrophobic sand (green diamonds).