Abstract: Flock fibers suitable for use in the manufacture of pile fabrics and materials by electrostatic flocking are treated to improve the electric conductivity of the fibers as well as enlarging the range of humidity in which the fibers retain good conductivity, flow, gliding and spring capacity characterstics. The process comprises treating the fibers, such as polyamides, polyesters, polyacrylonitriles and cellulose triacetate, with an aqueous solution containing a water-soluble alum, and tannin. In a preferred embodiment, the treating solution also includes a water-soluble alkali- or ammonium salt.