The mask carver -the undagi tapel– is a specialized craftsman who has likely come to his calling through heredity.
The sacred aspect of the mask comes from its treatment by the carver, the wood that is used, the magic letters inscribed inside it, and the spirit power it receives in the pasupati or ngerehun ceremony held on an auspicious day.
As the carving process itself is sacred, the temple priest, carver, and villagers select propitious days to cut the wood and begin the carving process.
The choice of the tree from which to secure the wood is also extremely important. Sacred trees include the pule, waru taluh, kayu kepah, kayu jaran, and especially the kepuh rangdu, in which the spirit of Banaspati Raja`s soul is said to reside. Pule is used for common masks. Both kepuh and pule are strong but not thick, and are light in colour.
The carver first shapes the raw wood with a hand axe. The outline of the face and its features begin to appear. The forms are further refined by flat and smooth chisels. The carver sits cross-legged, usually on a woven mat, steadying the wood with his fee, since both hands are required for carving. r
Using a knife to create detail, the carver searches out obscure and stubborn areas, especially the eyes and nasal-labial folds. The back of the masks is cut out with a curved knife, and concave areas are shaped to accommodate the facial places of the wearer. Eyes are carved out.
The next step, the process of painting, varies. For sacred masks, traditional paints made from ground, calcified pig jaw or deer horn must be used as a base. Secular masks are colored with imported, commercial paints, and the painting process is much fster than for sacred masks.
Trim is finally applied. Facial hair, most commonly from goat skin, is cut to shape and attached with knotted bamboo fasteners. Holes are punched next to the ears, and cotton string with a rubber strip made of old inner tire tubes secures the masks to the wearer.

Extract from Balinese Masks: Spirits of an Ancient Drama – Judy Slattum