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Here you go, see you get a real tutorial from one of the best forum members. You probably don't want to oxidize the whole blade to dark level like charlie does, so you'll have to modify it but you...

No, that would be too strong, you're looking at vinegar level stuff. Warm vinegar can work, play on another blade first see what you can get with the color.
I'm only a casual amateur that toys with...

May be try darkening the groves of the etching/engraving - basically you develop a black oxidation/ patina across the whole surface with a weak acid and then lightly sand the surface to shine leaving...