Yellow Thermochromic Pigment, Temperature Sensitive 18°C, 1–10μm – KTP-18-BY

Yellow Thermochromic Pigment, Temperature Sensitive 18°C, 1–10μm – KTP-18-BY

Special Effect Pigments › Thermochromic Pigment Series

KTP-18-BY is a Yellow thermochromic pigment with an activation temperature of 18°C, in the fine 1–10μm particle size range — a microencapsulated leuco dye pigment that is yellow below 18°C and becomes colorless as temperature rises above the threshold. At 18°C activation, KTP-18-BY sits in the cold-indicator range alongside the 16°C and 17°C grades — reliably yellow at refrigerator temperature and reliably colorless at normal room temperature, producing a clean visual signal that a product is at the correct cold serving condition. The fine 1–10μm particle size makes it compatible with printing inks, coatings, and nail lacquer systems where smooth film formation is required.

18°C Yellow — Positioning Within the Cold-Indicator Range

Within the Kolortek thermochromic series, the 16–22°C grades are the cold-activation group — these pigments are colored at refrigerator temperature and become colorless approaching room temperature. KTP-18-BY at 18°C is yellow in this cold state. Yellow is visually distinct against dark backgrounds and provides high contrast on labels and packaging — a practical advantage over colors like malachite green (KTP-17-MG) for applications requiring high-visibility cold indication in print. The two-degree difference between the 16°C red grade (KTP-16-BR) and KTP-18-BY allows formulators to create dual-color temperature-responsive designs using both grades simultaneously.

Technical Specifications

Cold-Range Thermochromic Grades — Activation Temperature Comparison

Multi-color designs using two or more thermochromic grades at different activation temperatures allow sequential color changes across a temperature range — for example, combining KTP-16-BR and KTP-18-BY creates a red-to-yellow-to-colorless progression as temperature rises. Each layer activates independently at its threshold.

Key Technical Characteristics

Yellow at cold, colorless at warm — high contrast for cold-indicator design: Yellow provides strong contrast against dark backgrounds — black, navy, dark green — which makes KTP-18-BY effective for cold-indicator labels where visual impact at low temperature is the design brief. When the temperature rises above 18°C, the yellow disappears cleanly to colorless, revealing whatever is beneath: a static graphic, contrasting text, or a different color. The base coat determines what the warm-state visual looks like; the thermochromic layer controls what appears when cold.

Using KTP-18-BY in multi-layer temperature-responsive designs: Because different thermochromic grades activate independently at their respective temperatures, formulators can stack two or more grades to create sequential color changes across a temperature range. KTP-16-BR (red, 16°C) and KTP-18-BY (yellow, 18°C) printed in separate layers or zones will both be colored below 16°C, then the red disappears first between 16–18°C leaving only yellow, then the yellow disappears above 18°C. This creates a three-state visual progression — both colors, yellow only, colorless — across a 2-degree temperature window. Practical bench testing is essential to confirm the transition sequence and visual separation in your specific ink system.

Microencapsulation and the critical low-shear processing rule: KTP-18-BY consists of leuco dye chemistry encapsulated within polymer microcapsules. The microcapsule wall maintains the controlled chemical environment that enables the thermochromic reaction. Any processing step that fractures the capsule — high-shear dispersers, ball mills, three-roll mills — permanently disables the color-change function in those particles. Add KTP-18-BY to fully prepared ink or coating base using low-shear paddle mixing only, after all other dispersion steps are complete.

Kolortek has produced thermochromic pigments across a range of activation temperatures and colors for over 20 years, maintaining consistent activation temperature calibration and capsule quality across production batches. A BPA Free yellow thermochromic grade is also available at 32°C (KTP-32-BY F) for food-adjacent applications requiring BPA Free compliance. TDS and SDS are available on request for KTP-18-BY.

Application Range

Frequently Asked Questions

Q: What is the practical visual difference between KTP-18-BY and KTP-16-BR on a dark label?
A: Both grades are colored when cold and colorless when warm — the difference is color and the 2°C separation in their activation thresholds. KTP-16-BR gives red at cold; KTP-18-BY gives yellow. Over a dark base, both produce high-contrast visible color when the product is cold. If both grades are printed in the same design, the red disappears first as temperature rises (at ~16°C), then the yellow disappears (at ~18°C) — creating a brief intermediate yellow-only state between the two temperatures before both are gone. Whether this sequential change is visible in practice depends on how quickly the product moves through the 16–18°C range and the loading levels of each grade.

Q: Is there a BPA Free yellow thermochromic at 18°C?
A: The BPA Free (food-grade) yellow thermochromic available from Kolortek is KTP-32-BY F at 32°C — a higher activation temperature grade. A BPA Free yellow at 18°C is not currently listed in the standard range. Contact Kolortek to discuss whether custom activation temperature options are available for BPA Free food-grade yellow specifications.

Q: Can KTP-18-BY be used in UV-curable ink systems?
A: Yes, with care. UV-curable systems are compatible with microencapsulated thermochromic pigments provided the UV cure cycle does not generate excessive substrate heat that activates the pigment during curing — if the substrate temperature rises significantly above 18°C during cure, the pigment will be in its colorless state during the cure window and the printed color may appear uneven. Test under your specific UV cure parameters (lamp intensity, line speed, substrate) before production specification.

Request Samples or Technical Data

Thermochromic performance — transition sharpness, color intensity, and cycling durability — varies with ink system, film thickness, and substrate, and must be confirmed by bench trials before production. Contact Kolortek to request a sample of KTP-18-BY alongside adjacent temperature grades, download the TDS, or discuss multi-layer thermochromic design options for your application.