[Amps] Pre-heating of tubes

[Peter Chadwick]

Will said:
>Under 300 deg C which is just under where you can't see the anode turn red in the dark, is where zirconium will not do any good at all, neither for hydrogen or O2 and the others. These heat colors work for any metal, but not for graphite. You can check them against any heat treatment or metalurgical chart.<

According to my book on heat rreatment (Hardening, Tempering and Heat treatment, Tubal Cain, Nexus  Special interests, ISBN 0 85242 837 5) in a dim natural light, 700 deg C is dull red, 740 blood red, 800 cherry red, 825 bright cherry red, 850 red, 900 bright red and 1000 deg C is yellow. Not to be confused with the pale straw through dark blue used when tempering steel. I would be surprised if 300 deg C can be seen, even in the dark - unless maybe, you are a pit viper!
73
Peter G3RZP