  In this work, we study ageing behavior of aqueous laponite suspension, a
model soft glassy material, in creep. We observe that viscoelastic behavior is
time dependent and is strongly influenced by the deformation field; the effect
is known to arise due to ageing and rejuvenation. We show that irrespective of
strength of deformation field (shear stress) and age, when imposed time-scale
is normalized with dominating relaxation mode of the system, universal ageing
behavior is obtained demonstrating time-stress superposition; the phenomena
that may be generic in variety of soft materials.
