Abstract The effect of the properties of the granulation liquid, i.e. viscosity (amount of binder) and surface tension on residence time, torque and granule properties such as size, shape, structure, strength and flowability was studied in a co-rotating twin screw granulator. An increase in the viscosity of the granulation liquid increased the residence time and torque. The granule size distribution reached mono-modality and their strength and flowability increased at high viscosity. The reverse was observed with a decrease in viscosity. The surface tension of the granulation liquid had only a minor influence on the residence time, torque and granule properties.