The Technology Behind Scratch and Sniff Stickers

Popcorn, root beer, strawberry, and pizza — those are just some of the familiar smells we remember from scratch and sniff stickers as kids. But there is an interesting technology behind scratch and sniff stickers that make it all possible, and it has even been used to entice adults into buying products based on their smell.

The smell from a scratch and sniff happens, of course, when the sticker is rubbed. How does the scent happen, and why can it sit in a box for ten years and still give off a scent when it’s scratched? The technology wasn’t initially invented for stickers that could have a scent. It started when scientists were looking for a way to have carbonless paper.

To make a copy of a document wasn’t as easy as sticking it in a copy machine. The machines weren’t around. A piece of carbon paper had to be inserted between other pieces of paper, which was a messy process. A scientist at 3M in the 1960s came up with and patented a process of micro-encapsulation that allowed copies to be made without carbon paper. 3M found that they could use the patented process for something else — to hold a smell from scented ink. Scratch ‘N Sniff was born in 1965.

The micro-encapsulation process for scratch and sniff stickers begins when scented oil is mixed with a polymer in a reactor. It’s blended by a rotary blade at…