This pipe has started to cake.
But see those dark black spots that used to be brown briar?
Whatever capillary system that briar had is roasted and toasted there, all the way through.
But the briar sort of merges with the cake to create a heat sink.
This isn’t common. The old Kaywoodie I own that has two black spots are on the V bottom of a Bulldog.
I had an expensive hand made freehand with a black spot that burned all the way through. The carver was in Arizona, and I contacted him, but he had cancer.
I own too many pipes to add to his troubles, so I kept it to show what defective briar is.
Burnout is why the old timers kept a cake the thickness of a dime. Get out in the wind and a pipe can burnout easily.