Method of fragmenting and/or weakening a material, in particular rock or ore, by means of high voltage discharges, comprising the steps: a) providing a process zone between at least two electrodes arranged at a distance relative to each other, which process zone is flooded with a process liquid,; b) feeding through the process zone the material that is to be fragmented and/or weakened; c) generating high voltage discharges between the at least two electrodes while feeding the material that is to be fragmented and/or weakened through the process zone for fragmenting and/or weakening the material; d) feeding process liquid into the process zone and discharging process liquid from the process zone while feeding the material that is to be fragmented and/or weakened through the process zone and while generating high voltage discharges between the at least two electrodes; e) determining a degree of turbidity of the process liquid in the process zone or near the process zone or of the process liquid discharged from the process zone or determining a difference in the degrees of turbidity of the process liquid fed into the process zone and of the process liquid discharged from the process zone; f) comparing the determined degree of turbidity with a reference value for the degree of turbidity or the determined difference in the degrees of turbidity with a reference value for the difference in the degrees of turbidity; and g) changing the generation of high voltage discharges and/or of the feeding of the material through the process zone depending on a detected deviation of the determined degree of turbidity from the reference value for the degree of turbidity or of the determined difference in the degrees of turbidity from the reference value for the difference in the degrees of turbidity in such a manner that, when subsequently the steps e) and f) are repeated, no deviation is detected or the detected deviation is smaller. a) providing a process zone between at least two electrodes arranged at a distance relative to each other, which process zone is flooded with a process liquid,; b) feeding through the process zone the material that is to be fragmented and/or weakened; c) generating high voltage discharges between the at least two electrodes while feeding the material that is to be fragmented and/or weakened through the process zone for fragmenting and/or weakening the material; d) feeding process liquid into the process zone and discharging process liquid from the process zone while feeding the material that is to be fragmented and/or weakened through the process zone and while generating high voltage discharges between the at least two electrodes; e) determining a degree of turbidity of the process liquid in the process zone or near the process zone or of the process liquid discharged from the process zone or determining a difference in the degrees of turbidity of the process liquid fed into the process zone and of the process liquid discharged from the process zone; f) comparing the determined degree of turbidity with a reference value for the degree of turbidity or the determined difference in the degrees of turbidity with a reference value for the difference in the degrees of turbidity; and g) changing the generation of high voltage discharges and/or of the feeding of the material through the process zone depending on a detected deviation of the determined degree of turbidity from the reference value for the degree of turbidity or of the determined difference in the degrees of turbidity from the reference value for the difference in the degrees of turbidity in such a manner that, when subsequently the steps e) and f) are repeated, no deviation is detected or the detected deviation is smaller.