easterntraveler:
First, welcome to the forum!
Unless the previous owner used a lighter on the pipe, I'm guessing that you're not so much dealing with "char" as with. . . well, "gunk." I've found that the best way to remove this kind of build-up is with saliva, a clean and lint-free handkerchief or rag, and lots of elbow grease. I don't personally recommend alcohol -- which I think should be kept as far away from a bowl's exterior as possible, for fear of damaging the finish -- or even vinegar, which, while a fairly mild solvent, can still damage a finish. Depending on the extent of the build-up, you should probably be prepared to spend maybe 15 minutes, with multiple applications of saliva and lots of rubbing.
BTW, this is assuming the pipe has a smooth finish on the top of the bowl. If it's a sandblasted or craggy top, I'd encourage you to check the Pipe Maintenance/Repair section of the forum here for more-specific tips.
Bob