What sort of experiment would be sufficient to test the foam hypothesis?
Can foamy boiling water in a tube without electrolysis be used informatively?
Do I need dewars, or will graduated cylinders be good enough?
It seems that a graduated cylinder is good enough:
(From http://jlnlabs.online.fr/cfr/diycfr/index.htm , with detailed instructions)
But to reproduce the same amazing effect shown in the videos of the 1992 boil-off experiment, I think it is necessary to use a cylinder with the same dimensions of the F&P cell and replicate the same electrolytic process.