A video by Sentinel76 gives an intriguing view inside an electric arc furnace with the power turned on. The furnace works by running a powerful electrical current through an electrode to heat its contents into liquid steel.
What you’re seeing here is the arc between the tip of an electrode and liquid steel, which is hidden under nearly a foot of slag (the bubbling liquid you see here). This video was recorded entirely by chance, I was videoing other things when I realised that I had a clear view of ‘A’-phase. I had to use two crossed polarised filters in order to block out enough light to see things clearly – and yet the arc itself is still blue-white and indistinguishable!