Production of Indelible Script

A method to produce indelible script on a paper substrate provides for the introduction of at least one highly penetrating coloring compound having at least two reactive functional groups into the substrate. An oxidation dye in the script is subjected to oxidative polymerization within the paper substrate itself. A liquid composition is disclosed having a solution of at least one oxidation dye with functional groups in a concentration of 0.01 % to 40% by weight, such solution including up to 80% by weight of a suspension of carbon black and a solution of an oxidant.