Want invisible ink? Just put water in your inkjet

Cosmos Magazine - Wed 25 Sep 19

But you’ll need this special paper to make it work. Mark Bruer reports.

Coated paper holds secret messages that can be erased with a hairdryer

Newscientist - Wed 25 Sep 19

When paper with a special manganese-based coating is printed with water, the message is only visible in UV light – and it can be erased with a hairdryer

Secure printing with water-based invisible ink

Phys.org - Wed 25 Sep 19

Researchers in China have developed a rewriteable paper coating that can encrypt secret information with relatively low-tech invisible ink—water. A message printed out by a water-jet printer ...

Secure printing with water-based invisible ink, Eurekalert - Wed 25 Sep 19
Secure printing with water-based invisible ink, ScienceDaily - Wed 25 Sep 19