Paint that changes color at different temperatures is known as thermochromic paint. The color change occurs as the compound structure of pigment molecules within the paint react to the increased temperature, which means that the paint absorbs or reflects light differently. With most pigments, this color change occurs at temperatures above 81º F and returns to normal when cooled. There are two methods of creating thermochromic paint, one involves the use of liquid crystals, and the other uses leuco dyes combined with chemical compounds. As thermochromic paint is a relatively new invention requiring in-depth scientific knowledge, the best way to make it is to purchase pre-made compounds and combine them with paint.
Combine desired amount of acrylic paint with acrylic medium in mixing bucket, approximately one part of medium to 10 parts acrylic should suffice. Stir to achieve a smooth consistency.
Mix in thermochromic paste/powder and stir--initially add just a small amount (5 ml of paste/1 tsp powder).
Paint a test sample on a piece of scrap material: allow it to dry.
Heat test sample to over 81º F using a hairdryer; check the temperature with a thermometer.
If the desired color change is not achieved, add more paste/powder to mixture; stir and repeat process.
Once your test sample displays the correct color change, proceed to paint the designated object. Paint one coat, without allowing painted areas to dry before the remainder is completed; otherwise the color change will be uneven.