Acid based plating solution plates a very dark gray (anthracite) color, almost black. Can be used alone or as a contrast color on both yellow and white metals. For bath plating only, cannot be used for pen plating. 4 oz. bottle has 100 ml of solution containing 2 grams of Ruthenium. To make a 1 liter bath, stir contents of bottle into 800 ml deionized water. Umicore Black Ruthenium 475 is strongly recommended to be plated over an undercoat of 18k for proper adhesion. When plating over non-precious metals, plate the item with gold prior to using Black Ruthenium. As with all liquids, Rhuthuna Black is not able to be returned or exchanged.