Hi Melanie, The stringy "black stuff" is either silver oxide or silver peroxide. It is formed due to the high voltage that most people use. Yes 27 volts is "high voltage" for the formation of silver oxide, which starts at 1.228 volts.
The best way to contain the "stuff" is to cover the cathode with a piece of new white shoe lace. Rinse it with hot water, squezze it, rinse with DW and slide it over the cathode. Most shoe laces are tubular in weave. At the end of the brew carefully with draw the electrodes and remove the shoe lace. Works great , use it often. "Ole Bob" -- The silver-list is a moderated forum for discussion of colloidal silver. Instructions for unsubscribing may be found at: http://silverlist.org To post, address your message to: [email protected] Silver-list archive: http://escribe.com/health/thesilverlist/index.html List maintainer: Mike Devour <[email protected]>

