Kinematic viscosity is structure-sensitive characteristic of melt. The polytherms of kinematic viscosity are plotted for LS59-1 brass at different temperature conditions. An availability of polytherm hysteresis under heating and cooling the melt testifies the nonreversible structural changes. Metallographic analysis shows a presence of α-, β-, and Pb-phases. The rise of zinc content from 36 to 39% results in the microhardness increase due to zinc redistribution and raised saturation of α-phase with Zn.