Modern copper powder production is realized on bar electrodes in the tanks of bunker type at constant current (I) which exceeds the limiting current (Ilim) on a smooth electrode. In the course of the formation of a dendritic deposit is periodically removed from the cathode bars by their shaking. At the moment of deposit removal the cathode surface decreases sharply and cathode potential shifts to negative region. Then dendritic growth on bar electrode enlarges true surface area of the deposit; current density Igr.fr. decreases, growth of dendrites into solution slows down, the rate of hydrogen evolution re-duces. Step by step current density decreases so that dense globules crystallize on deposit growth front. The dense compact copper layer an the surface of dendritic copper deposit prevents their subsequent removal from the cathode. By means of potentiostatic chrono-amperometry technique (CAM) it has been cleared up that transition to globule crystallization takes place within the cathode polarization interval ?E = 0,54 to 0,59 V. The following deposit crystallization leads to the formation of solid compact crust of "cathode scrap". One of the methods to prevent this consists in the correct choice of the period be-tween the removals the deposit from the cathode. The goal of the paper is to determine the optimal duration between the removals the deposit from the cathode for powder of ПМС11 brand by means of measurement the differential current efficiencies for hydrogen and copper during the electrolysis. The rod copper electrode 3,5 mm of diameter and 10 mm in height was placed in a glass cell (Fig. 1) with the solution containing 0,19 мole/l CuSO4 and 1,63 мole/l H2SO4 at 250С. Video recording of dendrite growth has been performed through the windows in copper foil anode. The evolving hydrogen has been col-lected and measured in a burett so that fresh solution hasn't distorted dendrite growth and velocity of gas evolv ing has been fixed with every 0,1 ml of the volume. Immediately after switching current hydrogen has violently evolved (Fig. 2) and created stormy convective electrolyte flows; the cathode polarization has been maximal in that period as well as the rate of dendrites growth (Fig. 3). As the area of dendrite growth front was increasing the cathode polarization was reducing. Correspondingly CE for hydrogen was decreasing and that for copper on was rising. The differential CE permits to determine the moment when hydrogen evolution stops; then copper crystallizes as globules and spherolytes. It takes 5200-5400 sec of uninterrupted electrolysis. This estimate agrees with the results of chronoamperometry measurements (CAT). The application of simulator for galvanostatic dendrite growth gives the expression for the calculation of the structural parameter of dendrite forming NrB2 (eq. 8), where N, m-2 - the displacement density for growing dendrite tops on growth front; rB, m is tip radii of that tops (fig. 4). The NrB2 dependence on N(?) and rB(?) is expressed by the eq. (9). The data of Fig. 5 shows that sharp growth of rB corresponds to globule formation. The sight of cross section for commercial electrode with formed cathode scrap is presented in Fig. 6.