Did you know that there are inks that, when introduced to certain temperature's, change colour? Often used in packaging processes where sterilisation is achieved using an autoclave, these inks are known in the industry as thermochromic inks, and in this article, we will explain how they work, where they are used and why they are so fascinating!
What exactly is Thermochromic Ink?
Designed for retort sterilisation of filled cans or plastic pouches, thermochromic ink changes from black to blue when the food package reaches the correct temperature of between 115 and 125 degrees celsius. Thermochromic ink can also turn transparent when heat is applied; an example of this type of thermochromic ink is found on the corners of an examinationmark sheet. This proves that the sheet has not been edited or photocopied, and also on certain pizza boxes to show the temperature of the product.
Why do we need ink that responds to heat in this way?
With the growing regulatory demands by governments for proper coding and marking on cooked food products, there is a growing need for reliable and cost-effective solutions. This can be especially important in the food industry, where heat-treated ready meals are becoming more popular for convenience. Equally, there is a consistent demand for solutions that can be applied to products such as baby food and pet food.
Thermochromic inks that change colour when the treated product reaches the required temperature fulfil this requirement and reverse when cooled. While thermochromic inks cannot guarantee that sterilisation has actually occurred, they assist manufacturers by providing a good indication that the process has taken place. While there have previously been challenges associated with this form of coding, thermochromic inks provide a reliable solution. Inks which do not reverse once cooled are Thermotropic inks.
Needham Ink Technologies' OEM compatible thermochromic ink can be used to print on both metal cans and plastic film. With excellent adhesion to plastic pouches, no pre-or post-treatment of the packaging substrate is required.
Giving good contrast on the dedicated white printing area, the ink offers a clear colour change from black to blue at temperature. It has an operating temperature from 5 to 40 degrees celsius, ensuring it can work effectively in a wide range of environmental conditions. Unlike some earlier generations of thermochromic ink, today’s innovation will not change colour prematurely due to temperature effects from the printer itself, rather than the sterilization process.
Thermochromic inks such as our 03955 formulation also dries quickly, ensuring optimal integration into fast-paced manufacturing processes, with a drying time of only one second on all materials. Our OEM compatible thermochromic inks are also smear-resistant. This ink serves as a good black to blue thermochromic ink, and also as a 'green' MEK free general-purpose black ink.
We hope that this blog has helped to shed some light on thermochromic inks and their uses. Here atNeedham Ink Technologies, we have decades of experience in providing reliable coding solutions and consumables you can rely on.
If you would like to learn more about our range of OEM compatible thermochromic ink formulations, you can get in touch with our friendly sales team: