Postcard sales and production are in decline, but collecting them is as popular as ever. Now An Post's using them to send a message to the future.

'GREETINGS FROM SUNNY (insert country here)! Saw (insert iconic sight here) despite noonday heat. (Insert annoying relative/travel partner here) sends love. Wish you were here."

It's standard postcard-speak, generally handwritten on one side of a dividing line that separates the greeting from the four short lines where addresses that no longer consist of four short lines are to be inserted.

Time was when it was common practice while on holidays to gravitate at some stage towards the nearest twirling wire rack of coloured images on standard 4in-by-6in card, and spend quality cafe time penning compact missives to those at home. These days, unfortunately for the time-poor or easily bored among us, travellers are more likely to indulge in lengthy group e-mails on digestive disorders and lost luggage - and these can't even be pinned to the fridge.

Is this the end of the line, then, for the postcard? If so, then at least it has had a decent innings, having been around since its first appearance in Philadelphia in 1861. The Austrian government issued its own version eight years later, and the rest of Europe soon caught on. Britain and Ireland allowed for the sending of pictorial postcards, as they were known, towards the end of the 19th century, although the concept of the divided back - where message and address appeared on the same side - was only authorised in 1902.

It was around this time that the postcard really took off. New inexpensive photographic processes allowed postcard punters to print snaps of stylised poses on postcard backing and send them into the world with a ha'penny stamp. The six postal deliveries per day that were common in Edwardian times meant that even same-day appointments could be made by card. Such was the ubiquity of postcards here and abroad that in 1908, according to figures from the US post office, more than 677 million postcards were mailed in a country whose population at the time was 88 million.

In Ireland, the political possibilities of the postcard were quickly spotted, and republicans and unionists alike used them to spread their respective messages. Postcards played a particularly significant role in documenting the events of 1916, depicting the ruined buildings of the aftermath as well as portraits of the leaders of the Rising.

The political postcard made a resurgence in Northern Ireland in later years, with hunger strike and anti-internment cards emerging in the latter half of the 20th century, and new ranges, including one on the issue of British state collusion in Northern violence issued by Relatives for Justice as recently as 2006.

MANY SUCH POLITICALpostcards are now worth considerably more than when they were first issued, according to Brian O'Neill, proprietor of Bygone Days in George's Street Arcade in Dublin, where tens of thousands of postcards are on sale. "I probably wouldn't have any for more than €100," he says modestly, but having been in the postcard business for some 16 years, he recognises that some are more valuable than others.

"People collect political postcards," he points out, adding that historical events are still popular subjects. "Obviously, anything to do with the Titanicor, to a lesser extent, the Lusitania, carries quite a high value."

O'Neill says many postcard collectors - or deltiologists, to give them their correct title - look for cards depicting particular places that have a personal significance. At his stall, the piled-high shoeboxes marked Kildare, Mayo, Dublin Central and even Japan testify to the importance of place.

Yet, despite the bursting boxes at Bygone Days, there's no doubt that postcard production has declined over the years, giving way to telegrams, telephones and finally e-mails, and to personal snapshots as cameras became more commonplace. Postcards persevered through the century in various guises, however, with white borders coming and going, and linen cards and even peat cards finally making way for the photochrome cards that arrived in 1939 and are still the most popular today. For many, they became synonymous with holidays, defining particular places to such an extent that photographers were credited with capturing the essence of an entire nation within 24 sq in, as in the case of John Hinde when he first began snapping Irish scenes in the 1950s.

These days, the influence of the postcard can still be felt, with tourists jostling to capture on their own cameras the same defining image of a famous site that has already been made iconic on the postcard stand that is always nearby.

While it's clear that both production and sales of postcards are down, O'Neill says he has seen no drop in the numbers interested in collecting them over his years in the business. He points to a new trend for collecting "rack" cards, the free postcards handed out as advertising in cafes, bars and shops, though purists may turn up their noses at the way these cards often have images on both sides, rendering them unsendable.

Just as the postcard has been harnessed for political and commercial purposes in its many changing forms, it has also made a surprising comeback in an entirely unprecedented form through an American project known as PostSecret. This began life as a blog that published postcards designed and created by anonymous members of the public, and revealing some heretofore hidden secret.

Its creator, Frank Warren, who has received more than 200,000 postcards to date and published a number of PostSecret books, says the project shows that the advent of new technology doesn't necessarily mean the demise of the postcard.

"I love the way PostSecret combines the most modern form of communication, blogs, with one of the oldest, postcards," he says. "Even more appealing is the idea that when a stranger mails me a secret that they have never shared with a soul, it is exposed to strangers for its full journey. And the card itself may even show evidence of its journey, like it has a life of its own."

HERE IN IRELAND, postcards are also the point of departure for a new collective art project sponsored by An Post. The brainchild of artists Teresa Doyle and Edel O'Reilly Flynn, the idea first took shape when O'Reilly Flynn was living in New York, where she developed a special affection for the postcard as a means of maintaining contact.

"Living away from home, text message is great, e-mail is fantastic (it's so quick), but being away and coming home from school or work and receiving something in the mail, there was something physically special about that," she recalls.

Together with Doyle, she began inviting people to create their own works of art using the postcard template.

"We wanted to revive the art of handwriting and its use as a way to communicate with each other, as well as the old tradition of physically sending a postcard," says O'Reilly Flynn.

"The postcard is like a snapshot," says Doyle. "It's something small, you can take it in your hand."

For Doyle, the handwritten message is as important as the image on the other side. "It's a very small task in one sense, and it's a big ask in another: how do you fine-tune your thoughts to get them into the postcard space?"

The postcards they received were mounted as an exhibition that caught the attention of An Post, which came on board to create the national C Both Sides project. It's an initiative which invites members of local and national communities to create postcards that will eventually be shown together in what, it is hoped, will become Ireland's biggest collective art exhibition.

They have already received hundreds of entries, with some well-known personalities, such as RTÉ's Joe Duffy, taking part. To ensure that everyone has the tools to participate, blank cards are being delivered to every house in Ireland, with the hope that budding artists, poets and deltiologists will breathe new life into this old medium and create a social document that brings the flagging 4in-by-6in format into the 21st century.

"Twenty, 30, 40 years from now, that collection of postcards will mark a time in a changing Ireland and a changing world," says Doyle.

So future deltiologists, line up your shoeboxes, as Ireland gets ready to wish you were here.

For more information, see www.anpostcbothsides.ie and postsecret.blogspot.com