Reversible hydrochromic inks for printing
Reversible hydrochromic inks react to water or moisture.
A white ink becomes transparent after contact with water, revealing a colourful design printed underneath.
When the ink becomes dry again, it returns to its original white colour. This type of hydrochromic inks react to water in a reversible way.
They are used for production of advertising materials and gadgets, toys, posters, moisture indicators etc. They are probably most widely used in colouring books for children.
A child paints pictures by using a paintbrush soaked in just water. The white ink, when exposed to water, becomes transparent, showing colourful pictures hidden underneath.