ABSTRACT
Particular care is taken to twist and turn the lament in the shape of a helix to minimize the heat conduction loss from the lament into the surrounding gas, which is generally an inert gas such as argon having a high atomic weight to prevent evaporation of tungsten. Before lling argon, the bulb is evacuated and any residual oxygen or hydrogen is absorbed by a suitable gettering compound incorporated in the bulb. is helps in keeping away from blackening of the bulb. Inclusion of a small percentage of nitrogen along with argon aids in avoidance of arcing inside the bulb during lament failure.
