Thermochromic (or thermochromatic) printing is not new. Using inks that change color with heat, from colorless to colored, or vice versa, is fun, interesting, and appealing. Naturally, such application is popular in packaging and commercial printing.

Just recently, Coca-Cola Turkey launched a summer promotional series of ten new beverage cans using thermochromic ink technology. Colorless at ambient temperature, the images of ice cubes, palm trees, sandals, and sailing boats turn colorful when the drinks are sufficiently chilled for consumption. The United States Postal Service, on the other hand, commemorated the solar eclipse of August 21, 2017, with a series of thermochromic postage stamps, where the black circle in the center of the stamp turns into an image of the full moon when pressed with a finger. More commonly found is perhaps the Pizza Hut box with its heat-activated thermochromic sticker, where an all-white dot with a red “Hot” in the middle means fresh, hot pizza while a black one equals a new, hot pizza, free of charge.

Within the book industry, however, thermochromic inks have always been applied in bits and pieces within a larger object: the cover of a book, or specific parts of an assessment or workbook to reveal answers to tests, for instance. The SeaBEAN trilogy by Sarah Holding is one case in point: The covers are heat-sensitive, and the dark cover of the first title turns into a seascape image when touched, and reverts to its original state when the cover cools down.

So Penguin Frozen Book, a collaborative effort between Penguin Random House China and Hunan Juvenile and Children’s Publishing House, is most unusual. It is the first “frozen” book that utilizes 100% thermochromic inks throughout its content pages.

Printed by R. R. Donnelley (Shenzhen) in May, the 20,000-copy first printing of Penguin Frozen Book came with its own set of challenges. “The print production team spent nearly one year conducting technical tests, such as to determine the optimal thickness of the paper, the proper force of the squeegee, and the correct temperature for the freezing and thawing process,” says Gary Liu, manager of the book technology center at Donnelley. The reversible high-temperature thermochromic inks change from full colors to clear when activated, and revert to full colors when the temperature drops.

Given that the storyline is about global warming and the disappearing habitats of animals such as penguins and polar bears, the application of thermochromic inks is most appropriate. (And no other company is more suitable to work on such a topic than one that uses the penguin as its mascot and namesake.)

“Each copy comes with a clear plastic box to protect it from moisture when kept in the refrigerator,” says Demi Miao, editor-in-chief of children’s book division at Penguin Random House China, adding that “the packaging makes the book, at 15cm x 25cm, resemble a block of ice. The text and graphics on all 24 pages are 100% visible when the book is frozen. Once it gets warmer, the text and graphics starts to disappear. In fact, this book can only be read for about 15 minutes before every page fades away to white. It sends a poignant and strong message about disappearing ice caps on our fragile planet.”

Retailing at CNY 258 (or approximately $37.40), more than 26,200 copies of Penguin Frozen Book have been sold thus far.