These pictures were sent to me by a shofar maker I deal with over in Israel.
This is how it starts with a bag of hollowed horns, uncleaned, unpolished …
They have them shipped in this way, the bone core has already been removed by the supplier … this requires soaking he entire horn assembly in warm water for a few days which accelerates the natural bacteria to eat away the thin membrane of tissue between the bone core and the outer “shell” we save as the horn which is basically the same material as our fingernails but thicker. Once the lining is eaten away sufficiently, the bone core can be untwisted from the outer horn, which is what is showing in the pics.
Here is another shot of the first phase.
Here is the owner, Eli, doing a “half-polish” (where the inside curve of the shofar is sanded and polished smooth but leaving the outside curve with the natural texture)
This is Eli applying a full polish (both inside and outside receive the same smooth finish)
Here, the mouthpiece is opened up at the end into a concave “bell” creating the pressure chamber into which the user blows. The inside contouring of the mouthpiece looks just like that of a trumpet mouthpiece.