Abstract: What is disclosed is a method of processing and/or recycling materials, especially thermoplastic materials, wherein the material is agitated and mixed m a receiving vessel (1), especially a cutting compressor or a preconditioning unit (PCU), and optionally also heated, committed and/or softened, wherein the material in the receiving vessel (1) remains in the form of pieces or particles and unmoltenthroughout, and—wherein the material in piece or particle form being agitated within the receiving vessel is subjected to inline spectroscopic and/or spectrometric analysis and/or measurement wherein die measurements ascertained in tins way are employed to obtain information about the material being analysed in each case, especially quantitative and/or qualitative indices of the respective material.