In silver Digest V 102 #68, Ode Coyoye wrote: " ........... Stir speed: I've found that stirring too fast promotes a build up of a fuzzy grey deposit that grows opposite to the direction of the water currents. I believe this to be caused by water pressure keeping the size of the hydrogen bubbles so small that their bouyancy won't overcome their adhesion to the electrode and silver becomes deposited on the surface tension of the water/bubble interface. As the hydrogen bubble is stabilized in size by the coating, a new bubble forms and also becomes stabilized. Eventually, a structure forms on the electrode that falls off into the water as light grey chunks. Also, this build up is only semi conductive and slows the process [keeping the hydrogen bubbles forming slowly]...sometimes developing a feedback loop that just makes the structure bigger and deposits little silver into the water. The upside to a bubble system is that it might knock those hydrogen bubbles loose before the structure can grow............"
Polarity switching is the favoured method for avoiding silver and/or silver oxide plate-out on the cathode. Has anyone tried a rapidly spinning cathode; ie a rod of stainless or similar attached to the shaft of an electric motor? Perhaps the high shear at the liquid-solid interface will prevent plate-out. Properly done such an arrangement might kill two birds with one stone - provide the stirring and obviate the need for a polarity switching circuit. Mechanical complexity is not great - feeding current to the spinning rod via a flexible strip would be no great problem. Any thoughts? Kevin Nolan ken...@optusnet.com.au
