Thermochromic inks are paints that change their color under the influence of heating or cooling. The sensory threshold of the material mostly depends on the sphere where it is used. Due to its popularity, we can meet such a technology in various spheres including label printing, packaging production, car painting and so on. What is more, depending on the current temperature, the image either appears or disappears.
The active component is a thermochromic pigment. It provides the reaction of the coating to temperature. The amplitude of temperature fluctuations are from minus 15 to 70 °C. Thermochromic inks are enclosed in microcapsules. They have a round shape and the average size can reach 3-10 micrometers. The color pigments contained in the paint can be represented as liquid crystals or in the form of leuco dye. The reactive element can be to be mixed with different solutions. For instance, it can be mixed with acrylic, rubber or oil-based paints. The share of an active substance is from 5 to 30 percent by weight of the finished product. The paint is heat-resistant, non-toxic, has a good chemical reaction. Ig we speak about motor industry, it really helps to reduce the “greenhouse effect”.
Types of thermochromic paints:
1. Reversible. They change their color at a certain temperature. When it changes in the opposite direction, the pigment returns to its original hue. In other words, it is a reversible color conversion.
2. Irreversible. If the temperature changes again, the original hue can’t be restored. This kind of pigments can transform the color only in one direction.
The most popular type is the first one. It is even used in medicine to control the sterilization of surgical devices.
- Due to the fact that this ink changes its color under different temperatures, each type of this material has a characteristic activation temperature. For example:
- Below +20 degrees Celsius. Used for applying to dishes in which people mix soft drinks
- +29-30 degrees Celsius. It is suitable for surfaces that change color when exposed to body temperature(T-Shirts, magazines, booklets and so on)
- Above + 45 degrees Celsius. This material is for products that interact with hot temperature (mugs for hot drinks).
The process of applying thermochromic inks is not something that will catch our eyes. This type of paint is applied in the same way as other paints. When we do it using our own hands, is appropriate to use a roller, brush, sponge etc. The most economical one for applying is a spray gun.
If the surface is covered with water-based material, then after application it is necessary to give it some time to dry, which can be reduced by using hot air.
The color palette that is used for such pigments is wide. The most popular are the following colors: red, blue, pink, cyan, yellow, green, orange, purple, black and brown.
It is recommended to keep it away from direct sunlight, otherwise it will be inappropriate for applying. An ideal place to keep is a dry and dark room. Furthermore, it these paints are expired, they will change into a gel-like material that need to throw away.
As thermochromic inks are getting more and more popular, so the sphere of application is also getting wider and wider. Nowadays book have become one of these spheres. The most catching books are Penguin Frozen Book and To you by Yiota Demetriou.
Penguin Frozen Book.
Penguin Frozen book is one of the most wonderful books. It uses only thermochromic inks on its pages. Taking into account that the story itself is about global warming. Therefore the usage of such ink is relevant.
Each book is delivered in a box to protect it from humidity while keeping in the fridge. The package makes the copy looks like a real block of ice. The text and graphics are 100% visible when the book is frozen. When it gets warmer, the graphics starts to disappear.
This book is worthy pay attention to, because it is based on an intimate reading experience. There are a lot of unsent letters on all pages written in poetry, prose and so on. All of these letters are addressed to You, reader. But the point is the text is hidden. If we attempt to touch it with love, respect and warmth, it becomes to get clear, of course, because of thermochromic inks. Gentle touches help black pages become translucent.
All in all, thermochromic inks are an integral part of printing innovations. It is developing and bringing a lot of new ideas into this sphere. Now we see books and other spheres of application. But what is the next step?..