Attaining high PPM, or the relative concentration of the silver in the colloidal solution is not a difficult task.The key question to ask are you thinking of buying a Colloidal Silver generator from market then some point needs to know "Is your generator a constant voltage device?". If they answer "Yes" then you will be getting an uncontrollable device. It doesn't matter if the voltage is provided by a transformer/rectifier or batteries. Constant voltage generators are rudimentary and you will probably be unhappy with the device in the long run. They just aren't much good.