An apparatus for treating at least one animal skin substrate with a multiplicity of solid particles comprises a rotatably mounted drum for containing said animal substrate, said solid particulate material and a treatment liquor, said drum comprising an outlet opening and a closure. The closure can be moveable between a first position wherein said outlet opening is closed and the animal substrate, the solid particulate material and the treatment liquor cannot pass through the outlet and are retained within the drum and a second position wherein said outlet opening is open such that solid particulate material and the treatment liquor can exit the drum through the outlet opening. The drum can further comprise an apertured screen arranged at the outlet and configured to permit passage through the outlet opening of the solid particulate material and the treatment liquor when the closure is in the second position and to prevent passage thereof through the outlet opening of the animal skin substrate. The apertured screen is suitably moveable from the outlet opening to permit loading and unloading of the animal skin substrate through the outlet opening when the closure is in the second position. A treatment method using the apparatus is also disclosed.