Do your patina or blasting after HT, and after you have the blade sanded/polished to the degree you want.
BTW, every method of putting a patina/etch on a blade involves chemicals, that's how it works.... mustard, vinegar, lemon-juice, cold-blue etc. are all "chemicals". Simply using the knife to cut meat or veggies will expose it to "chemicals", and that's about as natural as you can get. H20 is a "chemical" and will etch/patina any blade in way that you probably don't want, given enough time.
Don't let the idea of "chemicals" intimidate you, not all of them are crazy-dangerous. Just sayin'.
Google is your friend. The search function on this forum works well, also.