The flow behavior of crosslinking polymer solutions as they transition from liquid-like to solid-like material determines success or failure in several applications. Blood clots clog arteries and veins to initiate the repair of injured tissue or to cause injury themselves. Inks for 3D bioprinting need to balance viscosity, crosslinking degree and cell concentrations to avoid clogging the nozzle of ink-jet and extrusion equipment. Clogs in these applications may grow to block the channel, disrupting further flow. Flow disruption is typically undesirable, expect in the case of injury repair, in which further flow of blood would worsen the injury. However, in flow situations that involve polymer crosslinking in flow through small channels, no single a priori theoretical or empirical framework describes the conditions under which material flows or stops flowing.