A small ceramic pot created expressly for the processing of this particular head is filled with water and put over a fire. The head skin is inserted into the hot water three times by the leader and then left to simmer for 30 minutes; anything longer than that may lead to the hair coming out. After that, it's removed from the water and placed on a spear to dry. The Shuar view the instruments used in their raids as spoiled after they're used. They leave their spears behind after the raid, they discard the skulls of victims and, similarly, after its single use, the pot used to boil the head skin is discarded.
The boiling action leads to a significant decrease in the size of the skin -- to about one-third its size -- but it is hot pebbles, sand and rocks that complete the transformation. After it dries, the sewing begins. In most cases the mouth is pinned shut using wooden pegs prior to boiling. After drying, the pegs may be left in and the mouth is further sewn shut by threading the top and the bottom lips together using fiber; this fiber is woven in such a way that characteristic strings typically hang down from knots along the lips in completed tsantsas. The eyes of the victim are likewise sewn shut as will the incision that created the initial flap along the back or side of the neck. What results is essentially a pouch, with the base of the neck as the only opening.
This serves as the entrance for inserting hot rocks that are rolled constantly around inside the head to prevent burning the skin and to cure the skin evenly to prevent distortion of facial features. As further shrinking occurs, smaller hot pebbles and finally hot sand are used to complete the curing process. The outside of the skin is held against a flat, heated rock to smooth out wrinkles, much like a clothes iron. A hot blade is pressed to the lips to dry them. Finally the head is dangled over a fire to finish the process, darkening and toughening the skin; charcoal ash rubbed over the skin darkens it further. This dry heat curing stage is carried out over a matter of days.
After a series of steps that takes place over the course of several days and in locations along the way from the raid back home, a tsantsa, a human head reduced to about one-quarter of its original size -- about the size of a fist -- has been created. While the head skin shrinks, the hair is not reduced, lending an odd, characteristic look to the small head with long hair attached.