ink

Out of idle curiosity, I was wondering about the properties of blood when used as ink. Writing in blood sometimes pops up in the cliche of signing a deal with the devil in blood. Apparently real-life practitioners of the occult sometimes use blood (mixed with sour salts to prevent it...

If one were to print using black ink on say, a fairly porous paper soaked in a suitable solvent, would I be right in saying that the ink would effectively separate out into various colours around the printed areas (these colours being the other tints within the black ink), I'm thinking in the...

New color-shifting ink can turn a variety of colours. They use diffraction from silicon dioxide spheres and are iridescent.