Packaging and beverages
Labels that indicate the optimal consumption temperature (beer, soft drinks, wine); caps and containers that visually confirm the drink is cold.
Thermochromic inks:
color change by temperature
Printing inks that change color with temperature. In the reversible version the color change returns to its initial state; in the irreversible version the change is permanent, for monitoring thermal processes.
Phenomenon
Thermochromism · microencapsulated
Reversible
−10 °C to 69 °C
Irreversible
65 °C to 200 °C
01
What they are and how they work
Thermochromic inks are printing inks that change color as the temperature varies. In international technical terminology they are called thermochromic inks, and the physical phenomenon that governs them is thermochromism. They allow a printed text or graphic to change color —or disappear completely— when heated or cooled, either reversibly or permanently.
The active thermochromic system is microencapsulated in capsules of 3–5 µm —about ten times larger than a conventional pigment— that isolate it from changes in pH, solvents and moisture. This protection is what allows it to be formulated as a stable printable ink.
Microencapsulation is common to all thermochromic inks: without it the active compound would degrade and could not be printed stably.
02
Technologies: leuco dye and liquid crystal
There are two families of thermochromic compounds, with very different behaviors and precisions. The choice determines the cost, robustness and precision of the color change.
| Technology | Principle | Accuracy | Typical use |
|---|---|---|---|
| Leuco dye · leuco colorant | Color former + developer + solvent that melts at the activation temperature. | ±3 °C approx. | ~95% of commercial applications |
| Liquid crystal · TLC | Chiral-nematic helical structure that reflects a narrow band of light depending on temperature. | ±0.5 °C | Precision thermometry |
Note
Leuco dye inks are the general-purpose type: more robust, economical and formulable in almost any printing system. Liquid crystal inks offer very narrow, precise transitions, but are more expensive and sensitive to UV light. In both cases, prolonged exposure to UV, extreme temperatures or aggressive solvents reduces the service life of the ink.
03
Reversible versus irreversible inks
The functional difference determines what each ink is for. A rule of thumb: if the goal is a repeatable visual effect, the ink is reversible; if the goal is to leave a record that a thermal threshold has been reached, the ink is irreversible.
| Reversible | Irreversible | |
|---|---|---|
| Behavior | Changes and returns to the initial state | Changes permanently |
| Cycles | Repeatable indefinitely | Single use |
| Calibration range | −10 °C to 69 °C approx. | 65 °C to 200 °C approx. |
| Typical function | Repeatable visual effect | Thermal threshold indicator |
| Characteristic use | Packaging, promotion, education | Process monitoring and traceability |
Reversible inks are ideal for promotional items, smart packaging (beer or soft-drink labels that indicate serving temperature), touch-reactive cards and educational or cosmetic applications. Irreversible inks certify that a product has reached (or exceeded) a given temperature —for example, verifying that a loaf of sandwich bread has finished baking or that a sterilization cycle has been completed.
What temperature and color do you need to monitor?
Tell us the activation temperature, whether you need a reversible or permanent color change, the substrate and the printing method, and we'll select the optimal ink or pigment. Free engineering support, temperature control specialists since 1975.
04
Printing methods and formulations
All the inks in the catalog are printing inks. The method and formulation depend on the type.
Irreversible inks
Designed for screen printing and flexography, all water-based. Intended for printing text or graphics on paper labels whose color change certifies that the product has correctly gone through its heat process.
— Methods
Screen printingFlexography
— Formulation
Water-based
Reversible inks
Much greater versatility of methods and formulations, given their broad demand and diversity of applications.
— Methods
Screen printingFlexographyOffsetGravure
— Formulation
Water-basedSolvent-basedPlastisolEpoxyUV-curing
Note
Because of the size of the microcapsules (3–5 µm), printing thermochromic inks usually requires more open screen printing meshes and a more generous ink application than conventional inks, in order to deposit enough active compound and ensure a visible color contrast.
05
Materials, substrates and pigments
The versatility of formulations allows the inks to be applied to a wide variety of surfaces. Color-change performance depends on the adhesion, absorption and thermal conductivity of the substrate, so the formulation must be adjusted to the material and the end use.
— Compatible substrates
PaperCardboardPlasticsWoodCeramicGlass
06
Industrial and commercial applications
Thermochromic inks are used in two broad application groups depending on whether they are reversible or irreversible.
Marketing and promotion
Promotional items, touch-reactive business cards, games and campaigns with temperature-revealed prizes.
Thermal process monitoring
Irreversible labels that certify baking, cooking, curing or drying on the production line.
Sterilization and healthcare
Irreversible indicators that confirm an autoclave cycle or a sterilization process has reached the required temperature.
Safety and signage
Hot-surface warnings that change color when the contact-risk threshold is exceeded.
Education and cosmetics sector
Teaching materials and cosmetic products with a color-change effect.
07
Frequently asked questions about thermochromic inks
01 What is the difference between a reversible and an irreversible thermochromic ink?
A reversible ink changes color when it reaches its activation temperature and returns to its original color when the temperature goes back to the starting point; the cycle repeats indefinitely and is used in packaging and promotion. An irreversible ink changes color permanently: once activated, it keeps the new color forever, which makes it ideal for certifying that a process has reached a given temperature (baking, sterilization, curing).
02 At what temperature do thermochromic inks activate?
Reversible inks are usually calibrated between −10 °C and 69 °C, with standard temperatures and colors available. Irreversible inks cover a higher range, between 65 °C and 200 °C, intended for industrial heat processes. The exact activation temperature is defined according to the application; for precise effects, custom formulations are available.
03 What method are thermochromic inks printed with?
It depends on the type. Irreversible inks are water-based, formulated for screen printing and flexography. Reversible inks accept screen printing, flexography, offset and gravure, in water-based, solvent-based, plastisol, epoxy or UV-curing formulations. Since the microcapsules are larger than a normal pigment (3–5 µm), a more open mesh and a thicker ink layer are usually used to ensure color contrast.
04 What materials can they be applied to?
Paper, cardboard, plastics, wood, ceramic and glass, adjusting the formulation to the substrate, since adhesion, absorption and thermal conductivity influence the result. Besides the printable ink, the compound is supplied as a pigment in powder, paste or pellet form, which can be incorporated into plastics to manufacture parts that change color on their own.
05 How long does a thermochromic ink last?
Its lifespan depends on the use and the environment. The main degradation factor is UV light, which reduces color contrast over time; extreme temperatures and contact with aggressive solvents also affect it. Leuco dye systems are more robust and economical, while liquid crystal systems offer greater precision but are more sensitive. For applications with sun exposure or a long service life, it is worth consulting the most suitable formulation.
What temperature and color do you need to monitor?
Tell us the activation temperature, whether you need a reversible or permanent color change, the substrate and the printing method — we'll select the optimal ink or pigment and get back to you with the appropriate solution. Free engineering support, temperature control specialists since 1975.