Water-Activated Graphics - Paper that reveals graphics and text when wetted

Text and graphics are printed on paper with a transparent hydrophobic (water-repellent) ink. The printed areas will not absorb liquids and will therefore keep the paper's colour, while the non-printed areas will turn opaque and reveal the dark base colour when wetted. The colour change is reversed when the paper dries; the paper can therefore be activated multiple times.

Used for:
Water-activated graphics are used to convey marketing messages on beverage coasters and labels. It is also used for greeting cards, ads in magazines, and lottery tickets.

Details:
The sample has a black base colour, but other colours are available. A permanent colour change can be achieved by using juice, cola, coffee, or other strongly coloured liquids.

Idea:
Use it for paper-based diagnostic indicators in which the travel of blood or urine can be controlled.

The sample:
You get a beer coaster where you can read the secret text by adding a few drops of water. You can dry and try out the sample multiple times.  

All samples come with a laminated information card, which includes contact details for the supplier.