Just an observation I have made of my pipes, I have two that have a tiny depression at the bottom of the chamber that goes below the, for lack of a better term, 'pipe cleaner trough' --- the small area where the pipe cleaner comes into the bottom of bowl; there is always a few grains of tobacco that have fallen in there and the ember never touches them. (Pete Pub Pipe and Savinelli 2614KS) Its just the way they were drilled. Therefore, I agree with all of the above. +1