Two-range thermochromic inks for printing
Two-range thermochromic inks are inks with a ‘temperature memory’ in a way. They colour at one temperature and discolour in another.
After reaching a temperature of change, together with its increase, the ink discolours and remains in such state even after decrease of temperature below limit. Only after reaching much lower, usually minus temperature, the colour returns to its original state.
Two-range thermochromic inks are used as indicators of reaching certain temperature as an alternative to irreversible thermochromic inks, which can be used only as indicators of high temperatures.
In case of two-range inks, the colour change after reaching the temperature is permanent, but until the ‘erasure’ of colour at a low temperature.