[Mikendebbie]

I found this thread from 2014 that is the same question I have now.
I was wiping down my rubber seals this morning with spray conditioner and some of my slideout bulb seals have this black goo on them and the spray conditioner does not remove it. I can sort of scratch it off with my fingernails. I am not sure what it is or where it came from. It has probably been there for a while. Acetone and WD40 were suggested in this thread from 2014. Has time and technology come up with something better for the present?