  Dilute Laponite suspensions in water at low salt concentration form repulsive
colloidal glasses which display physical aging. This phenomenon is still not
completely understood and in particular, little is known about the connection
between the flow history, as a determinant of the initial state of the system,
and the subsequent aging dynamics. Using a stress controlled rheometer, we
perform stress jump experiments to observe the elastic component of the flow
stress that remains on cessation of flow or flow quenching. We investigate the
connection between the dynamics of these residual stresses and the rate of
physical aging upon quenching from different points on the steady state flow
curve. Quenching from high rates produces a fluid state, G">G', with small,
fast relaxing residual stresses and rapid, sigmoidal aging of the complex
modulus. Conversely, quenching from lower shear rates produces increasingly
jammed states featuring slowly relaxing stresses and a slow increase of the
complex modulus with system age. Flow cessation from a fixed shear rate with
varying quench durations shows that slower quenches produce smaller residual
stresses at short times which relax at long times by smaller extents, by
comparison with faster quenches. These smaller stresses are correlated with a
higher modulus but slower physical aging of the system. The characteristic time
for the residual stress relaxation scales inversely with the quench rate. This
implies a frustrated approach to any ideal stress-free state that succinctly
reflects the frustrated nature of these glassy systems.
