  We report on a comparison between stress relaxations after an applied step
strain and stress relaxations during slow, continuous strain in a bubble raft.
A bubble raft serves as a model two-dimensional foam and consists of a single
layer of bubbles on a water surface. For both step strains and continuous
strain, one observes periods of stress increase and decrease. Our focus is on
the distribution of stress decreases, or stress drops. The work is motivated by
apparent disagreements between quasistatic simulations of flowing foam and
simulations of continuous strain for foam. Quasistatic simulations have
reported larger average stress drops than the continuous strain case. Also,
there is evidence in quasistatic simulations for a general divergence of the
average size of the stress drops that only appears to occur in steady strain
near special values of the foam density. In this work, applied step strains are
used as an approximation to quasistatic simulations. We find general agreement
in the dependence of the average stress drop on rate of strain, but we do not
observe evidence for a divergence of the average stress drop.
