Cake is the black carbon, but don't confuse that with black, wet tarry substance in a heel that hasn't caked yet. If you don't have a cake, try smoking 1/3 or 1/2 bowls until the heel starts to cake. The sides cake pretty easily after that. I clean the bowl on cobs, but never on briars. I just run a pipe cleaner through the stem after each smoke. I might take the stem off my pipes 2-3 times per year and do a more thorough cleaning, but not of the bowl. If you wipe out your bowl you will delay the formation of cake. After a cake is the thickness you want, wiping the bowl is not a bad practice, to keep it from getting too thick.