5th carbon arc laboratory session - Close up of the arc.

In this tonight's session, I performed more advanced observations about electrode wear, always with my experimental carbon arc electrode holder. The arc was running at 225W (30V, 7,5A). Here are the major conclusions:

- A pair of D size batteries will have an estimated lifespan of 45 min. to an hour in free air. Considering that enclosing the arc multiplies the lifespan by a factor of 10, those rods could last from 7h30 to 10h in my future automatic arc lamps!

- Being chemically optimized for batteries, the latter's formulation seems to generate more ash and slag, in addition of generating a curiously large amount of sparks! Those particularities do not affect the arc, but could pose some problems when I'll design the electrode holders and enclosing globe. It could be necessary to add a slag/spark arrestor just below the bottom electrode.

- Size 4 (from D batteries) carbon rods are a little too big for a 225W arc. Ignition is difficult due to the higher heat dissipation of the larger electrodes. Performances of ignition by an automatic mechanism in such conditions are at the moment unpredictable.

In the next session I will probably perform similar tests with size 3 rods (from C batteries). I will also probably design a new electrodes holder that will reproduce more accurately the arc position of the future automatic arc lamps.