Gunk in bathroom sink

[everyman46]

All through the fall and winter, my master bathroom sink flows free and clear..no problems. Now spring has come, and periodically from now through the summer I will get a build-up of a black, almost tarry gunk that grows up around the plastic sink stopper support, the flanged shaft that connects the round sink stopper to the push rod that comes into the drain plug. I have to take out the stopper, clean off the shaft, and hook it back up which is kind of a pain to keep it from clogging up. Any ideas on what it could be and how to keep it from forming? I'm thinking some kind of mold but it doesn't smell moldy or smell at all for that matter.

[HayZee518]

the human body has all sorts of bacteria, on skin, in saliva, and any other bodily discharges which build up inside your drain. slimy snot, saliva all contribute to this build-up. all I can say is to use an acid based drain cleaner to dissolve this stuff and flush it away.

[Redwood]

I do not advocate any acid or, caustic based drain drain cleaner.

I would recommend using a bacteria & enzyme based one only...