Editing Neon lamp (section)

===Flicker flame===
When the current through the lamp is lower than the current for the highest-current discharge path, the [[glow discharge]] may become unstable and not cover the entire surface of the [[Electrode|electrodes]].<ref name="Glow Lamp Manual">{{cite book |first1=C. R. |last1=Dougherty |first2=T. D. |last2=Foulke |first3=J. D. |last3=Harden |first4=T. L. |last4=Hewitt |first5=F. N. |last5=Peters |first6=R. D. |last6=Smith |first7=J. W. |last7=Tuttle |title=General Electric Glow Lamp Manual |edition=2nd |publisher=General Electric Company |date=1966}}</ref> This may be a sign of aging of the indicator lamp, and is exploited in the decorative "flicker flame" neon lamps. However, while too low a current causes flickering, too high a current increases the wear of the electrodes by stimulating [[sputtering]], which coats the internal surface of the lamp with metal and causes it to darken.

The potential needed to strike the discharge is higher than what is needed to sustain the discharge. When there is not enough current, the glow forms around only part of the electrode surface. Convective currents make the glowing areas flow upwards, not unlike the discharge in a [[Spark gap#Spark gaps as entertainment|Jacob's ladder]]. A [[photoionization]] effect can also be observed here, as the electrode area covered by the glow discharge can be increased by shining light at the lamp.