Foam stability was measured by recording the length of time
required for half of the pre-foam mass to drain (Phillips, Yang,
Schulman,&Kinsella,1989).A bowl with a 6-mm diameter hole in the
bottom was used for stability measurements. Immediately after the
final overrun measurement, the bowl was placed in a ring stand over
aweigh boat on a scale, with the hole uncovered. The time necessary
for half the mass to drain was recorded as the drainage ½ life. The
mass of foam removed during the overrun measurements (less than
20%)was subtracted when calculating half of the pre-foam mass. The
starting time for these measurements was taken as immediately after
foam formation. Each treatment was replicated a minimum of three
times to obtain average drainage ½ life.