These inks are also sensitive to water and certain chemicals but they also offer another particularity: they become fluorescent under UV rays once they have been in contact with water.
This type of ink is used in many countries to immediately detect an attempted fraud: if the printed document has been in contact with water, firstly the color will be washed out and then it will become strongly fluorescent if exposed to Ultra rays Violets.
These inks are to be printed in dry offset or letterpress exclusively: the visible color will not show any fluorescence but if the document has been “washed”, the ink will become fluorescent (especially in blue) and the maximum effect will of course be obtained on unglazed supports.
In this video, a damp finger, rubbed on the ink and under UV rays, reveals the protection provided by this ink.
