You might find this thread helpful. The hardest part is findind the arsenic trioxide. Other substances will darken a keris blade, but only arsenic will give you the correct colors, and even though, only if done properly. I would recommend that to make you initial attempts on some cheap blades, but even if you work on this one the process is, for the most part, reversable, as long as you don't seriously over-etch and eat away at the blade. That's kinda hard to do with pineapple juice or other fruit acids though.
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