  We investigate the process of shear melting and re-solidification of a
colloidal glass, directly after loading (pre-yielding) and after a series of
consecutive strain sweeps (post-yielding). The post-yielding glass shows a
significant softening compared to the pre-yielding glass, together with the
absence of history effects in successive shear melting protocols, indicating a
reproducible process of fluidisation and re-solidification into a glass state
unaffected by residual stresses. However, a significant hysteresis
characterises strain sweeps with increasing or decreasing strain amplitude. The
appearance of history and hysteresis effects coincides with the formation of a
glass state, whereas it is not observed in the liquid. We can describe the
onset of shear melting over a broad range of volume fractions and frequencies
using a recently developed model which describes the yielding process in terms
of loss of long-lived nearest neighbours.
