Illustration: Cathy Wilcox.

Illustration: Cathy Wilcox.

What do freshly cut grass, hot cross buns and coffee have in common?

Each smell has been used in recent ad campaigns that combined old-fashioned print with technology intended to convert smell into sales.

This weekend, supermarket giant Coles is placing ads in Fairfax, News Corp and West Australian newspapers carrying the scent of hot cross buns, with a special gadget being set up to spray the page carrying the ad as the presses roll.

Magazines have long included samples of perfume, and scented ads have been around in various forms for decades - Sydney newspaper historian Ken Sanz said Ad News in the '80s ran ads printed on art paper that you scratched to smell a particular scent.

But scented ads are becoming a more prominent form of niche advertising, and one that publishers are keen to embrace at the expense of digital rivals.

Rose-scented ads for Valentine's Day, the smell of strawberries and cream before Christmas, freshly cut grass for English Premier League and coffee-scented ads for Australian Coffee Week have been printed in recent years.

For advertisers, sensory advertising campaigns tend to be brief and designed to surprise. Ben Willee, of Spinach Advertising, said smell was a ''highly evocative scent and therefore very likely to cause a reaction with consumers. The real question is how much does it cost and what uplift in sales it generates.''