Montejano
Elite Cafe Member
The brown substance being 'drawn' on with the pen nib... is that a resist? Is there any chance of learning more about that process?
The technique is called "aqua forte" and used or taught in Fine Arts. The last century was used in Spain in cutlery, but was disappearing in the middle of the last century.
The brown ink is ink antacid. This ink can be bought already prepared in Fine Arts, although my family have our own preparation of the ink.
The technique is complex and needs many years of practice.
Poara learn more about this technique, you should read books on etching, used for intaglio.