Thermochromic inks can loose their original colour when the temperature increase and this is reversible.

For example a visible blue 27°C thermochromic ink will be coloured up to 27°C and will become progressively transparent when the temperature will increase above 27°C.

When the temperature will come back below 27°C , then the ink will be again visible blue. This reaction is always reversible.

The most usual temperatures  are 27°C and 35°C. With those temperatures it is possible to obtain a discoloration reaction simply by rubbing a finger on the printed area.

Inks can be printed by offset, letterpress, flexography, silk-screen and gravure, and usual colours are grey-black, magenta, and blue.

As a variation, inks can also change of colours according to the temperature selected, and in that case tose inks are called bi-coloured thermochromic inks.

Other tempeatures alos exist, such as 10°C which means that the ink will be  visible only below this 10° temperature.

Inks are manufactured with micro-encapsulated pigments, therefore an important deposit is always suitable and best intensity will be obtain by silk-screen process.