air here the transport device 2 expediently consists of a plurality of parallel polyamide or polyester filaments a distance apart between which spaces are left these filaments are shown on a larger scale in the drawing in practice their diameter is less than 4 mm a superheated steam feeding device connected to a superheated steam source is provided above the solidified plastic dispersion 4 provided on the leather 3 which superheated steam feeding device consists of tubes 5 having any desired cross section which are provided with outlet nozzles or outlet slots 6 from which expanded superheated steam emerges without pressure or at only low pressure in the direction of the solidified plastic dispersion 4 as a result hollow microspheres 7 are formed from the compact particles within a very short time when the leather 3 provided with the solidified plastic dispersion moves past so as to form foam coating which is nubuck like on its surface and has no skin on the leather without the properties of the leather being adversely affected thereby for better visibility the hollow microspheres are shown on a larger scale the number of tubes 5 arranged one behind the other in the transport direction 1 depends on the transport speed of the leather 3 and must be chosen so that treatment of the solidified plastic dispersion with expanded superheated steam in the short time span required for the formation of the hollow microspheres is ensured the distance between the outlet nozzles or outlet slots 6 and the solidified plastic dispersion.