Thermochromic inks are brilliant smart materials that change colour in response to a change in temperature. This can be achieved via body heat, such as using your hand to touch the material, or a stronger heat source like a hairdryer.
Mood rings are fun novelty items which demonstrate the effects of thermochromism in a very a simple way. Although the ring appears to turn a different colour depending on your mood, this change actually happens because of varying body temperature. Nowadays, thermochromics have helped to improve designs for scientific and applications such as thermometers, safety warning labels, clothing and baby accessories like feeding spoons. Since thermochromics change colour, this effect can create amazing eye catching graphics for marketing and branding to really help products sell.
Browse our colourful range of Thermochromic inks! They can be screen printed or applied using a foam gloss roller.
Is it magic?
We like to think so! Watch the video below to see Thermochromic ink in action and let us know in the comments . . .
The two types of Thermochromic Ink and how they work
Liquid Crystal / TLC (Thermochromic Liquid Crystal)
Liquid Crystals are a type of Thermochromic material that are in fact, exactly what their name indicates: a material with both the properties of a liquid and the repeated molecular characteristics of crystals.
Liquid Crystals, or TLCs, exhibit varying colours in response to the change in temperature. At lower temperatures, Liquid Crystals are mainly in a solid, crystalline form. In this state, TLC's don't reflect much light at all, therefore, appearing black. Apply some heat, and TLC's start to shift from black to all variations of red, blue and green. At the molecular level, when temperature rises, the space between the molecules of the crystals change, so they reflect light differently.
To create Liquid Crystals, they must first be microencapsulated into millions of tiny capsules only a few microns in size. As Liquid Crystals are very delicate, encapsulation protects the the thermochromic properties they hold. Next, these capsules are blended with other substances to manufacture different products, like room thermometers. As the temperature of a room changes, a Liquid Crystal Thermometer will display different colours. If the room is cool, the thermometer will appear black. TLCs allow precise measurement of temperature and can indicate cold or heat levels to within +/- 0.5 degrees or less.
As TLCs have such a delicate nature, they require specialist manufacturing equipment and facilities. Therefore, Liquid Crystal is one of the more expensive smart materials in today's market. SFXC Liquid Crystal products are on offer for the best price we can. The rainbow effect is so incredible we want everyone to experience it!
Leuco dyes and inks
Leuco dyes are microcapsules about 3 to 5 microns in size containing a colourant, organic acid and a solvent. They feature a more robust chemical makeup than TLCs, which prevents them from reacting or being damaged by other chemicals.
When Leuco dyes are kept at lower temperatures they appear coloured. The solvent remains in a dense state, since the colorant and acid are kept in close proximity to one another. When a Leuco dye is heated, the solvent warms up. The colourant and acid start to separate and the Leuco dye appears clear or translucent. So when patterns, words or other colours are printed on an underlying layer of ink, heat allows these visuals to be revealed.
Coors beer are a great real life example of a brand that has incorporated leuco dyes into modern design. Their beer can packaging featured a graphic of a mountain, and at room temperature, the mountains appear white. Yet when cooled to the perfect drinking temperature (around 7 Celsius), the mountains change to a bright blue colour. Once the beer warms up again, the mountain reverts back to white. This change isn't a one time thing! If cared for properly (that means no excessive exposure to UV or heat), Thermochromic materials can repeat this effect over and over.
In most cases, Leuco dyes can also be mixed with another colour, so as the temperatures changes, a two-tone colour effect can be achieved. For instance, if you mix blue and yellow together, the ink will be green at a low temperatures but yellow when the temperature rises.
Get our Thermochromic Green to Yellow colour switching ink here!
Or you can buy our trial pack that includes all the colours available in our colour switch range!