PROCESS OF PREPARATION OF AN AQUEOUS GEL INK WITH VARIABLE COLOR COMPRISING SILVER NANOPARTICLES

A process for preparing in situ an aqueous gel ink with variable color comprising the following steps: (i) preparing a gel-based matrix of aqueous ink comprising an N-Acyl-aminophenol, wherein the hydroxyl group is preferably in meta or para position on the benzenic group, and (ii) adding a solution of silver salts to the gel-based matrix of aqueous ink prepared in step (i), to obtain an aqueous gel ink with variable color with silver nanoparticles disposed therein. An aqueous gel ink with variable color obtained according to process for preparing, comprising an N-Acyl-aminophenol, wherein the hydroxyl group is preferably in meta or para position on the benzenic group and silver nanoparticles. A writing instrument comprising an aqueous gel ink with variable color.