Ink stamps can be fun to make and use, and 3D printers are uniquely positioned to create quality stamps of all kinds with just a little care. As with most things, the devil is in the details and th… ...

The “anti-groping” stamps, manufactured by stamp-maker Shachihata Inc., allow victims of harassment to mark their assailants with invisible ink, and also provide a deterrent to would-be attackers.

Let the stamps be printed in "weak ink,' while the canceling is done with "strong" ink. The result will be that any attempt to erase the cancel-mark would remove the colored ink of the stamp ...

Indelible Ink for Home Quarantine: The Election Commission has allowed health officials to use non-erasable ink to identify home quarantine people infected with COVID-19 virus.