The etching was done over a few hours. In this case it contrasts the areas where the cable is forge welded to itself. When pattern welded steels with different steels are etched the different steels corrode and chemically react slightly differently creating a color difference between the steels.
Thank you to Luis Montez for his expert sledge work. Do not use galvanized or coated cable for forging. These are the most common kind and will release poisonous fumes.
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