You can make your own high quality IS(Ionic Silver) or CS ( Colloidal Silver ) with DW(Distilled Water) a current control and a stopwatch. Current and time determine ppm of silver. See Faradays calculator/equations. With making the silver yourself you control how clean the equipment is and how careful you are in making it. Your cost per 500ml @ 20ppm will be under $0.10! The silver wire or bar will last a very long time. I have been making my own for years and just built a generator for my two daughters since I now have grandchildern! They bought the silver and I built the generator (around $25.00) So now they have IS & CS to use and a nebulizer for colds & flu.