 Low-mercury designs of lamps may fail when mercury is absorbed by the glass tube, phosphor, and internal components, and is no longer available to vaporize in the fill gas.Loss of mercury initially causes an extended run-up time to full light output, and finally causes the lamp to glow a dim pink when the argon gas takes over as the primary discharge.Subjecting the tube to asymmetric current flow, effectively operates it under a DC bias, and causes asymmetric distribution of mercury ions along the tube.