I have trained myself to avoid touching surfaces outside my home. I guess my college microbiology training has helped. Silver works much better, but I guess it depends on the long term colour change you are looking for, green or black. Perhaps an alloy works like our pre 68 coins which were 80% silver. A two hour window with copper would not be much good on a public door. Anyway I regularly go to the mall and never touch a door as I can nudge the handicap switch with my elbow. On public transit I rarely touch anything unless the driver isn't waiting for people to take their seats before gunning the accelerator. That's why you should always carry some hand sanitizer. These products look worthy if the price is right. Mike like expensive stuff 😁🇨🇦