These pieces have been thrown then burnished to a super smoothh finish. This allows the feathers, hair and other combustible materials to come into contact with the surface of the piece more effectively. The pieces are heated to around 800 deg c and then feathers etc are applied to the surface. The resulting carbon from the burning items penetrates the pourus surface of the clay to become permanant part of the pot. The burnished surface is sealed with wax to create a sheen on the surface.