The receipts you take home from the store – or stuff in your bag, or lose in your car -- employ a printing method that’s been around since the 1970s. Thermal printing involves heat-sensitive inks called leuco dyes that show up when they react with an acid developer embedded in the paper.

Not only do these inks fade easily, but receipts that use them aren’t recyclable, and could even be dangerous to your health.

Taking a cue from a failed experiment, scientists are developing a new kind of receipt paper that will use the same thermal printers without leuco dyes. Instead of acid developers, this paper is coated in reflective microspheres that collapse under heat, allowing regular ink underneath to show through.