: I have this smell that comes from the sink in our bedroom. Awhile back we had a cloge so I used a plunger….While doing this, all this black scum like stuff emerged from the area behind the sink..the overspill area. The plunger stirred up all this stuff…most of it gone but the remaing stuff still smells and after awhile is builds up again. What is this stuff?? Is it caused by my wifes makeup? a Soap? What can one use to get rid of this scum? Please help, : Thanks, : JohnIts caused by all of the above, use a chlorine based cleaner to remove it all. Pour it in the sink waste and let it sit for as long as possible.DISCLAIMERAll advice is given with-out seeing the job, and hence all advice MUST be taken as advice with limited knowledge on the exact situation. NO responsibility can or will be taken. And yes, I am a licensed plumber with my own business in Brisbane Australia