Tanning begins with the dye section. Stripped of its hair, the hide undergoes a slow surface tanning over a period of about four weeks, opening its fibers to absorb the tannin. The hides are passed through several pits, connected in a closed circuit through a system of pipes and containing different concentrations of tanning fluid. The hides themselves hang on frames and are moved manually from one pit to the next on a daily basis.
The second stage of the preliminary tanning involves a pit half filled with tanning fluid. The hides are submerged in the fluid with a layer of the shredded tan substances between each one. They remain here for approximately six weeks, after which the procedure is repeated in a second pit.
The oak-bark ground-tanning is an extremely gentle process taking place in old, three-metre deep oak lined pits. During the course of this process, tannin is absorbed into the hide binding and conserving its protein-structures. Nature supplies the main ingredients for the tan mixture used in traditional oak-bark ground-tanning; primarily oak, spruce and mimosa bark as well as valonea fruit.