When I'm finally finished with the rust treatment I'll post the blade before I try an etch with super strong coffee. Right now the blade is in a heavy coating of De-corroder wrapped in plastic wrap to keep it from drying out too quickly.
Something occurred to me about the subject under discussion: there are many variations in quality of steel and pamor material; would this difference not interfere with a consistent result in whatever rust treatment is involved?
/5/20
Well, here are pictures of this blade after treatment with Metal De-corroder (a Renaissance product) a hot rinse and before any etching has been attempted.
It was quite crusty and the color difference was not aparrent; no before pics, sorry.