Abstract: The method of optimizing the metering of charge-reversal agent into broke in the form of a suspension of fibers from paper treated in a coating machine and to be reintroduced into the production line, is distinguished by the fact that a partial stream is branched off from the main broke flow, the volume flow of the main stream and of the partial stream is measured, the turbidity of the partial stream is determined, downstream thereof the charge-reversal agent is added in a quantity that varies with time and, following that, the turbidity is again measured, in that the optimal metering rate is determined from the change in turbidity caused by the charge-reversal agent, and the said metering is carried out in the main stream in proportion to the mass or volume flows.