I use Archer Etchant from Radio Shack. I mix the etchant with water, about half and half. I clean the damascus with acetone and dip the damascus in the mixture for a couple minutes, take it out and see how it looks. I re-dip for a couple more minutes and then soak in water/baking soda mix to neutrilize the mixture.
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In the first photo of this thread, the third knife is finished and headed to it's new home. It has titanium frame, CPM154 stainless blade. I've attached a pic of it.
Thanks for looking,