I had a go with the 5% nitric solution today. I have two pattern welded knives on which the patterns are not well defined & my plan was to etch them until it was!
I cannot submerge the blades as they have grips on them, so repeatedly painted the solution onto the steel with a feather. Apparently, they are not affected by the acid.
The result was that the pattern did become a bit more defined, but although detritus washed off the steel each time I swilled it with fresh water, there is no noticeable depth of etching. I've left them to dry & will see what a repeat does this afternoon
Regards,
Kim Siddorn