The invention provides a method for producing prion protein having an aggregated conformation by contacting native conformation prion protein with aggregated conformation prion protein in a liquid preparation and subjecting this to at least one cycle or to a number of cycles of application of shear-force for fragmenting aggregates of prion protein, wherein the shear-force applied is precisely controlled. In addition to this process for amplification of aggregated state prion protein from native conformation prion protein, the invention relates to the aggregated state prion protein obtained by the amplification process, which aggregated state prion protein has one conformation, which is e.g. identical within one batch and reproducible between batches, e.g. as detectable by proteinase resistance in a Western blot.