Reconstructed Roman writing tablet. Object found at the Museum of London | MOLA 2012
Ancient Romans used ink, usually made of rubber and soot, to write on papyrus and parchment. They used red ink to better visualize the titles.
The ancients also knew the “likeable” ink. Pliny the Elder mentions the tithymalos plant (known as tithymalos characias), which was referred to as a “milk plant” or “goat’s lettuce”. Writing the inscription with its juice, it is invisible after drying; in order to show the content, it was enough to sprinkle ashes1.