[clarii_d] is currently finishing up her thesis project on thermochromic pigment to silkscreen receipts. The idea behind it is that when a receipt is touched, part of it fades revealing a hidden message.
As you can guess, thermochromic paint is a type of substance that changes color when introduced to heat — or in this case, fades altogether. Remember when mood rings were all the rage? Same thing.
In her project she is using silkscreening to transfer text onto the back of receipt paper using regular ink. Once dried, she silkscreens an image over top of the message, this time using a thermochromic pigment. The result is a slightly obscured image, but after holding it for a few seconds, it disappears and only the text remains.
Color-changing anything is a bit gimmicky, but we think [clarii_d's] project is a pretty cool and unique application of it. A few years ago we shared another interesting project utilizing thermochromism; a color-changing clock face that utilized the heat given off by resistors!