amount of collapse decreased and transient time increased dramatically in higher volume fraction samples. For concentrated samples with colloid volume fraction above 0.55, it took more than 4 weeks to see tiny collapses of less than half a millimeter at the very top of the meniscus. These collapses were distinguished from normal sedimentation by their characteristic sharp and non-flat boundary between the collapsed material and a clear supernatant. No crystallization was observed in these samples however long they were left undisturbed. Interestingly, for non-crystallizing samples with very high colloid volume fraction and polymer concentration (crosses), characteristics of both hard-sphere glass and transient gels were present. After 4–8 weeks, tiny collapses were seen, and also a thin layer of crystal phase appeared just under the collapsing boundary.

Consider a sequence of samples of similar colloid volume fraction and increasing attraction, for example samples A-H in Fig. \[fig:phasediag\] with $\phi\sim0.6$. According to thermodynamic equilibrium theory, all these samples should crystallize [@cptheory]. Sample A without polymer was a glass. Sample B with a small amount of polymer was also a glass as no homogeneous crystallization was observed for 4 weeks and only heterogeneously nucleated crystals at the meniscus were observed after 13 days. 