Thermal polish is a colour-changing nail polish that contains thermochromic microcapsules with a leuco dye, which switch between two colours as the nail warms or cools, often showing a gradient at the cooler tip.
Also known as: thermal nail polish, colour-changing nail polish, mood polish, thermochromic polish
Thermal polish contains thermochromic microcapsules, each 1 to 10 micrometres across. Inside each capsule are three things: a leuco dye, a weak acid and a solvent whose melting point is set at the switch temperature. When the solvent is solid, in the cold, the dye is coloured. When the solvent melts, in the warm, the dye turns colourless (Lab Muffin).
Makers blend the leuco dye with an ordinary pigment. On a warm nail the leuco dye is invisible and only the base pigment shows. On a cold nail both show together, so the colour looks deeper or shifts to a second shade. The tip of the nail is cooler than the base, which is why many thermal polishes show a gradient, or ombré, with the second colour at the free edge.
The change is reversible and happens in seconds. A cold drink, cold water or a winter walk trigger it. A hot shower turns the whole nail to the warm colour. Thermal pigment is sensitive to ultraviolet (UV) light and is often reported to weaken after weeks of sun exposure; this comes from user reports and not from a published study.
Thermal polish is applied like any regular lacquer, in two thin coats under a top coat. It is one of the finishes in the India Anaïs lacquer range, which is sold out until the next edition planned for spring 2027.