ABSTRACTThe Bostwick consistometer is a durable and simple instrument that is widely accepted in industrial practice to evaluate product consistency. Flow observed in the Bostwick consistometer was evaluated as a balance of forces; the resulting expression yields the Bostwick measurement as a function of trough geometry and fluid properties. Experimental measurements for four Newtonian fluids verify the theoretically predicted dependence of the extent of flow on the kinematic viscosity to the – 1/5 powe