Carbon steel that has been blued can turn to a plum color over time. Sometimes carbon steel comes out of the blueing bath with a plum color. The plum color in carbon steel can be the result of the steel alloy, higher chrome, nickel and silicon content will make blued steel look plum colored, or the condition of the bluing salts. Cast steel usually has more chrome and silicon in the alloy, so it often comes out of the blueing tank with a plum color.

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