In the 16th century etching developed into the most needed printing technique in all of Europe. Thus woodblocks were displaced, losing importance with the invention of lithography and later photography. For this reason it remained above all an artistic printing means instead of something more practical and economical.
I honestly don't know, but my best guess would be the highly concentration salt solution because usually salt dehydrates things.
Black Market? this is just a guess but it's two words so yeah
