In the study of thixotropic substances and of materials of non‐Newtonian behavior, it is important to obtain complete flow curves (rate of shearversusshearing stress) which are taken in accordance with a standardized procedure. The time interval for any given increase or decrease in rate of shear should remain constant. A recorder which draws complete flow curves has been developed as an attachment for a Couette type of viscometer. The deflection of the bob, which is proportional to the shearing stress, is plotted against the speed (r.p.m.) of the cup which is proportional to the rate of shear. For precise measurements the bob suspension spring must not be subjected to any friction load; therefore the recorder uses sparks generated by a high voltage to puncture the recording paper. The sparking electrode is moved by the bob deflection spring while the paper is moved perpendicularly to the electrode motion by the transmission handle, the position of which controls the cup speed. A number of measurements made with the recorder are shown. The recorded flow curves permit immediate interpretation and calculation (without any replotting) of the plastic viscosity, the yield value, and the thixotropic behavior of the tested materials. Also, a method is proposed for determining the plastic viscosity and the yield value at initial agitation, which are identified as ``the initial thixotropic viscosity'' and ``the initial thixotropic yield value.''