Metal Effects primer is a unique water-based acrylic primer. Unlike other primers, it is especially formulated to block Metal Effects patina aging solutions and activators from reaching the metal, wood or reactive substrate. This helps prevent the formation of rust or other oxidation products from forming under the paint film. Metal Effects primer will also block out alkali salts, tannins, acid salts or other unwanted contaminates from bleeding through to the Metal Effects reactive metallic paint film and causing adverse reactions and unwanted color changes in the oxidized finish.