I spilled some ammonium nitrate on the garage floor, and while sweeping it up, I got the idea of disolving it in water, and dropping in a bright steel screw. I dont know where I got this idea, but I did need to darken a bolt for a project. Well, it worked. It turned a deep, dull, black. upon drying, it did develope some red rust, but the rust brushed off, leaving the black.
BTW, I had the ammonium nitrate on hand from an experiment in non-electric cooling, not for nefarious purposes.
BTW, I had the ammonium nitrate on hand from an experiment in non-electric cooling, not for nefarious purposes.