Abstract: An apparatus for the rotational coating of a surface of a substrate with a fluid, in particular the surface of a wafer with a polymer liquid, especially with a photoresist includes a rotary plate (2) for receiving the substrate (11), a drive device (3) for rotating the rotary plate (2), a dispensing nozzle (4) for the application of a predeterminable quantity of fluid onto the surface of the substrate (11) for the purpose of forming a layer (12) and also a pump (5) for conveying the fluid, the pump being connectable, on the one hand, to a source (20) for the fluid and, on the other hand, to the dispensing nozzle (4). A viscosimeter (6) is provided with which the actual viscosity of the fluid can be determined by physical measurement prior to the application of the fluid. Furthermore a corresponding method is proposed.