I suggest applying a lower potential, say 4 Volts. That would make the glow
a more orange color, maybe more impressive, without risk to the filament and
a lower bulb temperature.

On the other hand, are you sure this tube is defective? Good tubes are
worth around $100 and I'm sure you can find a shorted one for very little.

Due to the high current drawn by the filament, it's common for a poor socket
contact to cause excessive heat at the tube pin, melting the solder and
causing the filament to go out. There are many tubes out there that have
been scrapped with the thought that the filament is burned out, when in fact
the tubes are repairable. (I just repaired one for a fellow amateur.)

Bob