I have been thinking about this for probably a year, but:
I have been trying to remember what itype of ink we used in art class in high school ---- The teacher had dispersed the ink into tiny container for us to dip our stick from a tree into and we drew a line or fern in the case of my class. Then after we completed the fern drawing, we used plain water and with a small paintbrush, paint over the line (or next to) and thus bled the ink into either the negative space (BG) or the leaf itself. It created nice shading.
I always thought it was India ink, but I don't think so now. When I try India ink at home and it dries, it won't move (which makes sense since it's waterproof when dry); if I get the wet paintbrush to the ink before it dries, it will bleed. But from what I recall, in high school we drew out the entire fern first then used water to it….thus drawing was more than likely dry; but it still bled with the water.
Anyone know what ink this was from my story? Right now I am either thinking the art teacher added something to India ink to keep it wet or moveable later….or it was a different ink I don't know about. It was black ink…that when it bled, the shading was a purple shades.