A sticky business

It is a Sunday in 1974 in St Paul, Minnesota, and Arthur Fry, a chemical engineer who sings for the choir at his local Presbyterian church, is once again annoyed with his hymn book. There are two Sunday services and Fry marks the pages in his hymnal in the time-honoured way, with scraps of paper. But they fall out. Why, he wonders, has no one ever invented a sticky bookmark? Eureka!

All glued up and nowhere to go

During the week, Fry worked in the product development division of the American company 3M. On the Monday following his brainstorm, he dug out the formula for an unusual adhesive developed by another 3M scientist, Dr Spencer Silver. This glue had "low tack", which means that it stuck but didn't bond tightly. Its outstanding feature was that it could be peeled off without leaving any trace. Dr Silver had thought his "unglue" was interesting enough to demonstrate it to his colleagues, but none of them could think of a use for it.

Taking advantage of a policy called "bootlegging", which allowed researchers to spend 15 per cent of their time on their own projects (the theory being that this fostered inventiveness), Fry began to experiment. After many hymn book pages had been glued inseparably together, he came up with a "repositionable" note that we would recognise as a Post-It, but which the marketing department at 3M saw as an unsaleable curiosity.

The Post-It is that rare thing: a genuine invention. New products constantly appear, but nearly all of them are refinements of earlier versions of the same thing. In marketing terms, the Post-It met an "unperceived need" - no one could see the point of it.

But 3M, as a company, embraces innovation. Its boast is that at any time, 30 per cent of its sales derive from products that are less than four years old. Founded in 1902 as the Minnesota Mining and Manufacturing Company, it built a fortune making different kinds of sandpaper, and developed a reputation for being good at coating things with adhesive. It was a 3M lab assistant, Richard Drew, who invented first masking tape and then Scotch tape in the Twenties. The company now produces 900 different kinds of sticky tape (along with 60,000 other products) so sticky notes weren't a completely alien idea.

They went ahead with test-marketing, but the results were disappointing. Then someone noticed that, where free samples had been handed out, sales had been very good. This observation probably saved the yellow sticker from obscurity.

Message magic

Post-It notes - so called because of the American use of the term "post", meaning to stick up a notice - were launched in the US in 1979 and in Europe in 1981. They are now available in most of the 61 countries where 3M operates. Manufactured in giant rolls which are gummed, then trimmed to size, they sell by the millions. There are dozens of different shapes and sizes, 18 colours and 20 fragrances (fragrance encapsulation, which enables you to peel and sniff perfume advertisements, being another 3M technology). Post-It notes are now among the five top selling 3M products.

Art Fry, now retired, has made no money from Post-Its, but he has become a minor celebrity, featuring in Gap advertisements, that sort of thing. His brainchild must take its place alongside the fax machine, the mobile phone and the Internet as one of the great tools of the communications revolution. The technology - that strip of unglue - may be simple, but Post-It notes have altered the way we exchange messages. And they can't break down, or get lost in cyberspace