Based on my experience today I would also add that the substance used as the finish on briar can be an important factor in rim char. The first unsmoked Kaywoodie I ever bought was one of the 1970s lacquer-finish pipes. Although it is not a high-end 'woodie, I have always treated it with kid gloves. Until today I had been able to keep the rim pretty pristine. This afternoon I stepped outside to enjoy some unseasonably nice weather while smoking. There had been no hint of wind or breeze until I was finishing my light. A rogue breeze took a tongue of flame up over the rim. The lacquer touched by the flame instantly scorched and darkened. When I finished my smoke I tried the spit polish method only to find that much of the discoloration will remain until the day I decide to sand off the lacquer.