How coated paper and low-tech invisible ink could encrypt secret information

1

Paper is coated with chemicals which can absorb and emit light. Messages can then be printed on this paper with water using an inkjet printer

 

Print

and view

UV

2

The water disrupts the structure and properties of the chemicals so the invisible printed message shows up dark under short- wavelength UV light

Heat and

erase

3

When briefly heated under a hairdryer, the message disappears. So far, scientists have reused the paper up to 30 times

How coated paper and low-tech invisible ink could encrypt secret information

UV

Print

and view

Heat and

erase

Reuse

1

2

3

Paper is coated with chemicals which can absorb and emit light. Messages can then be printed on this paper with water using an inkjet printer

 

The water disrupts the structure and properties of the chemicals so the invisible printed message shows up dark under short- wavelength UV light

When briefly heated under a hairdryer, the message disappears. So far, scientists have reused the paper up to 30 times