Specification of a method for determining an apparent viscosity of resins in a liquid state, using one of the types of rotational viskosimeter described in this standard. A spindle or disc is driven at constant rotational frequency in the product being studied. The resistance exerted by the fluid on the spindle, which depends on the viscosity of the product, cause a torque, which is indicated by a suitable meter. The application of this method to specific products is detailed in annex A. The viscosimeters types A, B and C permit visscosity measurements from 0,02 Pa.s to 60 000 Pa.s.