Pipe mud is either cigar ash or pipe tobacco ash (can do a combo of both or either or) cigar ash I think hardens better but I prefer tobacco pipe ash myself, other threads here perhaps explain better than I but I just use an old tobacco tin lid and start putting all my ash in it, mound it up and then in center I put a few drops of honey to start (others again have used just water and ash combo...again I prefer a little honey w/water mixed into the ash which has great results for me) start mixing the wet into dry until you get a grout-like mixture, then take this mixture and coat the inside of your pipe bowl with it and (I put a doubled-up pipe cleaner inside the shank/into the bowl to prevent mud from cloggin up the draft-hole) once you have given a nice even coat to the entire bowl let this dry for a few days....that is it...it should harden and give you instant "cake" I only really do this for a cracked bowl or on my cobs...cake will build in briar pipes just from smoke'in and this is the ideal way of doing it...but if in a jam pipe mud has never let me down...others/comments...?