PSA: Not every Damascus cladded blade can be etched with coffee.
Someone posted a question about re-finishing damascus on a SG2 knife(stainless steel, stainless cladding), and the most upvoted comment recommends coffee, despite the fact that coffee basically does nothing to stainless steel.
(This is the gazilliont time this has happened hence the PSA)
In all fairness, the commenter didn't claim it would look the same, but considering how dark a coffee etch can turn out, when it's not stainless steel, it gives the impression that it would be relatively easy to create a similar look, which makes the comment, imo, somewhat misleading.
My friendly tip is to not mention coffee unless you're certain that the knife is carbon/non stainless and that it was etched to begin with, OR to include a disclaimer that it only works on carbon/non stainless.
Also, if there's ZERO patina on a used blade that's needs to be thinned and/or refinished, there's a 99,9% chance that it's a stainless steel blade, which means coffee or other mild acids won't do much to it.
Tl:dr - Stop telling people that they can etch their stainless damascus with coffee or other very mild acids. They can't which mean you're not actually helping them.
Ps. The knowledge of this place is vast and it's great that so many want to help out, but I believe we can do a little better when it comes to these type of very general answers to very specific questions.