I put a shiny coffee filter holder in dishwasher, and it turned dull grey. In the pic you can see the difference with filter cup, which retained silvery shine in the same dishwasher:
The holder leaves dark grey spots on kitchen towel, when I try to brush it.
I thought it is aluminum, but got confused by posts in internet stating it would turn black if washed in dishwasher. Mine is dull silvery grey.
What would the filter holder be made of, and is it safe to use it now, considering all the coffee drips through it into the cup?