Black to Red Color Change Thermochromic Pigment, 31°C, 3–10μm – KTP-30-BR

Black to Red Color Change Thermochromic Pigment, 31°C, 3–10μm – KTP-30-BR

Special Effect Pigments › Thermochromic Pigment Series › Colored-to-Colored

KTP-30-BR is a Black-to-Red color-changing thermochromic pigment with a 31°C activation temperature in the fine 3–10μm particle size range — a microencapsulated leuco dye pigment that shifts from black below 31°C to red above 31°C, producing a two-color visual transition triggered by body temperature or warm contact. The color-to-color shift (C2C) format makes KTP-30-BR distinct from the more common color-to-colorless grades — the color change is visible against any substrate color, not only dark bases, because the pigment maintains a visible color state on both sides of the transition. At 3–10μm, it disperses in printing inks, coatings, and nail lacquer without surface texture in thin films.

Color-to-Color vs. Color-to-Colorless — Why the Distinction Matters

Most Kolortek thermochromic grades are Colored-to-Colorless (C2CL) — they are colored when cold and become transparent when warm, revealing whatever is underneath. This requires a dark or designed base coat to create a visible warm-state result. KTP-30-BR is a Colored-to-Colored (C2C) grade — it shifts between two distinct colors (black and red) at the 31°C threshold. Both the cold state and the warm state are visibly colored, which means the color change is apparent on any substrate and does not depend on a specifically designed base layer for the warm-state visual. For formulators designing products where the color change itself is the primary visual — without wanting to engineer a reveal-layer system — C2C grades are the more straightforward specification.

Kolortek Color-to-Color (C2C) Thermochromic Series — 31°C Range

All C2C grades listed above activate at approximately 31°C — the body temperature threshold. The BPA Free series (KTP-31-RBF, KTP-31-GBF, etc.) covers the Colored-to-Colorless 31°C grades with food-grade compliance. Contact Kolortek for the complete thermochromic range including other activation temperatures.

Technical Specifications

Key Technical Characteristics

Black-to-red — maximum contrast color-to-color shift: Among the Kolortek C2C range, black-to-red produces the highest perceived contrast between the two color states. Black at ambient temperature shifts to saturated red at body temperature — a transition that reads clearly in both directions under standard indoor lighting without requiring specific background colors or base coat engineering. For nail lacquer, the shift occurs when hands are warm and reverses when cooled; for cosmetic products, skin contact at normal body temperature triggers the transition.

31°C — the body temperature standard: The 31°C activation threshold is calibrated to respond reliably to human skin contact and body warmth without activating under typical room temperature conditions (20–25°C). Products formulated with KTP-30-BR remain black in ambient conditions and shift to red when held, worn, or touched — a touch-activated or wear-activated color change. For cosmetic applications, the change occurs naturally during product wear. For packaging, activation requires direct warm-body contact rather than passive ambient temperature changes.

C2C substrate independence — practical advantage in nail and cosmetic applications: Color-to-Colorless grades require a designed base coat to create a meaningful warm-state visual — the colorless state reveals whatever is underneath, which must be pre-planned. KTP-30-BR shifts from black to red regardless of what is beneath. In nail lacquer, this means the color change is visible over any base coat and in any light direction — the shift is intrinsic to the pigment layer, not dependent on a layered design system.

3–10μm fine particle range: The slightly coarser lower cut of 3μm (vs. 1μm for C2CL grades at 1–10μm) reflects the C2C capsule construction, which typically produces a slightly different size distribution than standard C2CL grades. At 3–10μm, KTP-30-BR disperses in printing inks and standard coating systems without visible particle texture in cured films. For screen printing, confirm against mesh specification. Kolortek maintains consistent capsule size distribution and activation temperature calibration across production batches across 20 years of thermochromic production — TDS and SDS available on request.

Application Range

Frequently Asked Questions

Q: What is the main practical difference between KTP-30-BR (C2C) and KTP-31-BR (C2CL, Colored-to-Colorless) in nail lacquer?
A: KTP-31-BR (Colored-to-Colorless) is red when cold and becomes colorless when warm — the warm-state visual is the base coat or substrate color showing through. KTP-30-BR (Colored-to-Colored) is black when at ambient temperature and red when warm. In nail lacquer, KTP-31-BR requires a pre-designed base coat to create a meaningful warm-state result; KTP-30-BR shifts between two visible colors independent of what is underneath. For nail products where a bold dramatic color change is the brief — black nails that turn red on the hand — KTP-30-BR is the more direct specification.

Q: Does the black-to-red shift of KTP-30-BR work on white or light-colored surfaces?
A: Yes — because KTP-30-BR maintains a visibly colored state at both temperatures, the color change is visible regardless of the substrate color underneath. On a white substrate, black ink containing KTP-30-BR appears black at ambient temperature and red when warm. On a dark substrate, the same shift occurs. This is the core practical advantage of C2C grades over C2CL grades, where the warm colorless state depends entirely on the base to provide visual content.

Q: Can KTP-30-BR be blended with conventional black pigment to intensify the cold-state color?
A: Adding a non-thermochromic black pigment to a KTP-30-BR formulation will deepen the cold-state black but will also reduce the visual contrast of the warm-state red — the static black from the conventional pigment remains at all temperatures. The thermochromic component contributes the color-change red, but if it is surrounded by permanent black, the shift will appear as a dark red rather than a clean saturated red. Start with a small addition ratio and evaluate under your specific film thickness before committing to production loading levels.

Request Samples or Technical Documentation

The black-to-red shift of KTP-30-BR must be evaluated in your specific formulation and film thickness to confirm the transition clarity, loading level requirement, and activation behavior under your use conditions. Contact Kolortek to request a sample of KTP-30-BR alongside other C2C grades, download the TDS, or discuss the full thermochromic series for your application.