Scratch and sniff

Scratch and sniff technology generally refers to stationery that has been treated with a microfragrance coating. When scratched, the coating releases an odor that is normally related to an image being displayed under the coating. The technology has been used on a variety of surfaces from stickers to compact discs.

Use
Stickers became common in the late 1970s, and grew into big business for several companies throughout the early and mid-1980s. As the technology evolved to an "acid-free" design (commonly recognizable by the glossy appearance of the sticker surface, as opposed to the older, more matte appearance) the sticker craze seemed to come to a close.

Today, scratch and sniff stickers, in particular the older "matte" stickers, are highly collectible and sought after by collectors. Auctions for packaged stickers have seen bids go in to the multiple hundreds of dollars on eBay.

Samples of scratch and sniff stickers are used for detection of individual anosmia.

Production
Scratch and sniff is created through the process of micro-encapsulation. The desired aroma is surrounded by tiny micro-capsules that break easily upon scratching. Because of the micro-encapsulation, the aroma can be preserved for extremely long periods of time.

While there were hundreds of companies that put out Scratch and Sniff stickers, the most well known are Trend Enterprise's Stinky Stickers line, Hallmark, Sandylion, Creative Teaching Press (CTP), Spindex, Gordy, and Mello Smello.