An organic release agent is vacuum deposited over a substrate and surface treated with a plasma or ion-beam source in a gas rich in oxygen-based functional groups to harden a very thin layer of the surface of the deposited layer in a passivating environment. Aluminum is subsequently vacuum deposited onto the hardened release layer to form a very flat and specular thin film. The film is exposed to a plasma gas containing oxygen or nitrogen to passivate its surface. The resulting product is separated from the substrate, crushed to brake up the film into aluminum flakes, and mixed in a solvent to separate the still extractable release layer from the aluminum flakes. The surface treatment of the release layer greatly reduces wrinkles in the flakes, improving the optical chracteristics of the flakes. The passivation of the flake material virtually eliminates subsequent corrosion from exposure to moisture.