Thermal paint
Thermo colors (including thermal coatings , thermochromic coatings called) are paints , depending on the temperature its color change. They are used in technical applications in order to have a simple visual control of temperature changes. The underlying effect is thermochromism .
One area of application is e.g. B. with threaded busbars where the screw heads this paint can be detected quickly obtained so that the compound has loosened and contact resistances occur, causing a rise in temperature. It is important for this application that a contactless temperature display is possible. Thermal inks are also used in process engineering to quickly detect faults in which the temperature of system parts deviates from the setpoint.
Thermal inks are also used in advertising ; these are mostly lacquers that are black when cold and cover an underlying image. If you touch the giveaway with your hand (or fill a hot drink into a mug with this print), the image underneath with the advertising message appears as if by magic; when it cools down, the surface turns black again. These lacquers are applied using the screen printing process.
There are also thermal inks where the color change is irreversible . When heated above a certain temperature, these materials either undergo a chemical transformation (for example oxidation by atmospheric oxygen) or a change in structure through melting of the material. These substances are used to monitor the maximum temperature in furnace processes or to determine whether, for example, an electrical device has overheated.