Last weekend I filtered out the sludge, using the same filters I use for making my morning coffee, which I have done a couple of times over the past two years. The crud that accumulates at the bottom is not silver, as far as I know. I'm not a chemist, and would enjoy hearing from a chemist/chemical engineer/scientist as to what that stuff is. I recall having read somewhere that it is probably a sulfite or a sulfite/calcium sludge. I live in an area with very hard water, so that seems likely.