Most high carbon Damascus is etched in a ferric chloride mixture, then often given a finish etch in coffee. The first time I tried making a knife with stainless Damascus, I tried Ferric, but it didnt touch it. Despite trying for increasingly longer periods, Ferric brought out virtually no pattern at all.
The last two knives I have actually successfully made from this stainless Damascus, I have used hydrochloric acid for the etch. It does much better, with some pattern emerging within the first minute. Now I am just trying to work out how long to leave it in the etch, so thats still an ongoing process.