The nineteenth ink. Arsenic sulfide ground into gum arabic — the warmest yellow medieval scribes could afford, and the only one that killed the people who used it.
Click anywhere to grind a fresh stroke. The pigment ages downward as gravity pulls it through the paper. Each grain rings a chromatic pitch.
Scribes who illuminated psalters in poison gold died young and didn't know why. The pigment in your screen is a memory of the harm.