Warning: Disturbing Sludge

This is my bathtub. See that black stuff all around the tub? I think I know where that came from...


I decided to clean the overflow drain thingy. Innocent enough. It had a little gray stuff on one corner. So I removed this screw, and off came the cover....
This is what I found....THIS is what I found. Try clicking on the photo to enlarge it.

This is what it looks like now after a little cleaning and scrubbing.

DMC