Jim, If I understand you correctly, you want to repalce the silver cathode with copper.
If you do then in a little while you will have a silver plated copper cathode. Now you savant need not question that as I use a brass brazing rod all the time in my wide anode steup. It soon takes a beautiful silver plate. After all the CS process is a very poor silver plaring operation. If you wanted to inject some copper into you CS you might attach a small piece of #14 copper wire to the silver anode, be careful as too much copper is toxic. "Ole Bob"
