Abstract: A method of balancing a rotor. An epoxy resin balancing composition is applied to the rotor and the rotor is dynamically tested before the resin is cured. The resin composition includes fibrous inorganic material, which renders it cohesive, weighting material including powdered zinc and barium sulphate and a reactive polyamide, catalyst, and a diluent. The composition has a specific gravity of at least 2.0 and has substantially no slump at room temperature. The composition is sufficiently tacky, adherent, and cohesive to adhere to the rotor during dynamic testing before curing.