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
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
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