How do you make silver nano?

The most common device uses three 9-volt batteries in series to make a 27-volt DC source. This is hooked to two pure silver wires that are suspended in a glass of water. Some recommend using a salt solution to increase the conductivity of the water. With a salt solution it takes about 2 minutes to make a glass of colloidal silver. Others claim that the salt solution can cause problems and recommend to only use steam-distilled water. Without the salt it may take 45 to 60 minutes to make a glass of colloidal silver. The serious problem with this method is that you do not know when the process is done, and how many PPM of colloidal silver you made. Running a few extra minutes may burn the silver and create mud on the bottom and metallic silver floating on the top of the water. This may contain dangerously large particles of silver!