While wood glue works wonders repairing split shanks and cracks in bowls, Pipe Mud should be something every cobber is familiar with. If you win old/new stock cobs fron eBay, or remove the inner shank from a MM cob, Pipe Mud needs to be used to reinforce the often soft bottom of the bowl.
Yes, it's called Pipe Mud, because it's used on cob pipes, but it isn't made with pipe tobacco ash. Pipe Mud should be made from Cigar Ash, since such mud will be denser and stronger. All according to how many pipes you'll be working on, you need to collect ash for several cigars; real cigars, not little cigars or cheap ones made with non-tobacco filler. When you're ready to use the Pipe Mud, slightly break up the cigar ash, and add just a few drops of water or spittle, and miss a very stiff paste. I use a folded bristle pipe cleaner to apply a thin coating to the area needing to be reinforced. Waiting a minute or so, add several layers of Pipe Mud, and smooth it out. Set the repaired/reinforced cob aside for 3-5 days to allow it to harden and cure before smoking it. Maybe we should start calling it Cob Mud.