Today - as always at "A. Lange & Söhne" - blued steel screws are used because of their proven resistance to corrosion and also because they add highly decorative accents to a movement. The process of blueing (annealing) requires that the steel screws be slowly and cautiously heated to about 300°C. This produces an extremely thin cornflower-blue coating of shimmering magnetite that completely coats the steel.