The process of making amorphous ribbon by impinging a liquid jet on a substrate to form a steady‐state puddle from which the ribbon is drawn out by the moving substrate is examined. It is shown that lateral variations in the thickness of the ribbon across its width at any particular ribbon section are directly related to the puddle shape at an instant of time. Longitudinal dimensional variations in the thickness or width of the ribbon along its length indicate an unstable puddle whose shape varied with time. These longitudinal dimensional variations can be minimized by using nozzle geometries, jet velocities, and puddle sizes that induce uniformity and steadiness in the fluid flow. Various means to achieve such uniformity are suggested.