A method for blocking an optical element on an insert of a blocking device including: providing the insert of the blocking device, the insert being blocked in respect with the blocking device; providing thermoplastic material in a solid state in a first particulate form, the provided thermoplastic material having a feature included in an operating range; heating at least a part of the provided thermoplastic material at a temperature at which the thermoplastic material is in a melted state and flows under moderate pressure; providing on the insert an amount of the heated thermoplastic material for blocking one optical element; placing the optical element onto the thermoplastic material in the melted state; allowing the thermoplastic material to solidify, thereby blocking the optical element on the insert; converting the solidified thermoplastic material into a second particulate form, the converted thermoplastic material being intended to block another optical element.