RE: Do you think size of the electrodes has much to do with particle size or is it more about the amount of power that is being put out?
> Actually it works out to be both in this case, as electrode size, spacing and current, all work together in realizing the electrochemical reaction causing the formation of silver ions in solution.
RE: ...however the most important thing is still quality of silver.
> The rule of thumb is that 99.99 is more than enough to maintain a high quality solution. Though keep in mind that's it's unlikely to retain that purity as cross contamination occurs the moment you subject the rods to processing, cleaning etc. That said, it can't hurt to aim higher either. My take on silver purity is to try and strike a balance between cost and purity. 5 nines isn't likely reasonable, whereas 99.9 could carry risks of heavy metal contaminants depending on the foundry. As most foundries won't concern themselves with specific contaminants given that the silver is rarely if ever drawn for consumption.