It's reasonable to conclude that at the end of the boil-off, when voltage is 50 V and the liquid water is only a few millimeters, the cathode can easily reach the melting temperature of the plastic support.
that it is reasonable
and that the cathode can easily reach...175C
Without numbers, formulas and equations,
Physics is only foamy philosophy.
You said it could be explained easily ? Correct?
The only absolute value which has remained is truth"