Nice work Alan. I have another plate in the tank right now btw , running at 2.5V and 0.15A. This one was started on monday and will run until (at least) Friday.
I have been pondering something about the use of HCl with brass or iron cathodes. This was because Stevenson gave us the voltage data for his plates - which were brass. For a lot of the time the voltages he was using were below the Faraday limit so could not possibly break down water into H2/O2. I found this puzzling.
HCl will chemically attack iron or brass with the evolution of hydrogen. In the case of brass you can see the colour change since it preferentially leaches out the zinc component of the alloy, leaving copper behind- the colour goes from golden to rosy pink. I do suspect the HCl method is good in that chemical hydrogen is produced at the cathode surface underneath the plating, which together with electrolytic water breakdown -= H2 deposition from both sides. Also, my long ago Chemistry tutor told me that the hydrogen produced by the action of HCl on Zinc is monatomic - but he may have been wrong about that. I know that Frank Gordon has used zinc galvanised pipes as electrodes- this may also be important.
I am thinking of running another plate with an airstone in the tank (porous stone used in conjunction with a pump to aerate aquaria) connected in this case to a hydrogen generator. H2 is not very soluble in water but it might help to have a cloud of microscopic H2 bubbles being attracted to the cathode