I do not get residue in the bathtub, shower floor nor on my porcelain sinks from micas in soap. However, sometimes I have used too much mica and ended up with lather that was darker than intended and before rinsing out the sink, would see some slight color on the porcelain, but since I always rinse & wipe my sink after each use, there was no remaining residue left behind. Perhaps if not rinsed, it would leave residue, but I don't know as I am compulsive about leaving the sink clean after I use it. Shower water is more prolific than handwashing water, so I have never seen a residue remain after a shower either.