Both van der Waals and electrostatic forces of adhesion between toners and substrates play an important role in electrophotography processes employed in copying machines and laser printers. We report here a method of estimating van der Waals forces of adhesion between various substrates and toners of different particle sizes. The method involves the measurement of the detachment force and the resultant current caused by toner jumping between two closely-spaced conducting parallel plates. Conducting toners are first sprayed on the top surface of the bottom plate; the voltage across the two plates is then ramped at a constant rate. When the electrostatic force of detachment exceeds the forces of adhesion between the toners and substrate, there is a significant increase of current between the two parallel plates. The particles jump from the bottom plate and reach the upper electrode. Upon reaching the upper electrode, the initial induced charge is lost and the particles acquire electrostatic charge of the opposite polarity, then move toward the bottom plate. From the balance between the forces of detachment and adhesion (comprising of van der Waals, gravitational, and electrostatic image forces), the van der Waals force between the toner and test substrates can be determined.