A glow discharge starter having an hermetically sealed envelope containing an ionizable medium, a bimetallic electrode and a counter electrode located therewithin. A pair of lead-in conductors passes through one end of the envelope for electrically connecting the electrodes. A spot of dried paste is disposed on a surface within the envelope and comprises a mixture of thorium and a binder. The quantity of thorium is sufficient to reduce the dark effect of the glow discharge starter by improving the dark starting performance of the glow discharge starter.