This Saturday, we'll all be on the pull. But why do crackers make Christmas go with a bang?

Fancy pulling a Cosaque with me?

"Cosaque" doesn't have quite the same ring as "cracker", does it? But this is what the first Christmas crackers, created in the 1850s by Tom Smith, a London confectioner, were called.

Just imagine if it had stuck - the catch-all metaphor for Christmas stuff (think of all those "Christmas Crackers" lists of television programmes, foodstuffs and party frocks) would never have existed. And nudge-nudge lines about "pulling a little Cosaque" at the office party would have limited use, since Cosaque is French for Cossack, a Russian soldier.

The original name referred to the small explosive charge inside the cracker, known as the "snap", which was said to sound like the whips used by the Cossacks as they drove their horses through Paris during the Franco-Prussian War. It is a reminder of the origins of the cracker, which, like many things associated with a traditional British Christmas, have their roots in other countries - in this case France, Germany and China - and are of relatively modern origin.

Yes, but why does my cracker break with a "pfffft" rather than a satisfying bang?

It's because you aren't doing it correctly. Yes, there is a scientific way to pull a cracker, rather than just giving it a good yank and hoping for the best. QinetiQ, a science and development company, has listed six factors that combine to create the perfect pull:

1. Tilt your end of the cracker downwards to maximise the chance of its contents landing near you.

2. A firm two-handed grip should be taken to stop the cracker being torn.

3. The cracker must be pulled in a steady and controlled manner.

4. The distance to the centre of gravity of the cracker affects the quality of the snap.

5. The cracker must be made from high quality, strong materials in order to create a good snap.

6. Twisting makes it more likely that the cracker will tear in your pulling-partner's favour.

The historical bit

Tom Smith was on a visit to Paris when he saw bon-bons - probably sugared almonds - wrapped in coloured tissue paper. He decided that this would be a good addition to his range of sweets and table decorations in the run-up to Christmas in 1847. The bon-bons did well, but to stimulate trade for the new year Smith began placing a small motto or rhyme inside each one - an idea based on the Chinese August Moon festival, during which cakes containing goodwill messages are handed out. From here Smith began to package toys, novelties and keepsakes with his sweets, all of which went down well with the sentimental Victorians. The size of the bon-bons grew to accommodate Smith's latest novelties.

Aren't all crackers made in Far Eastern sweatshops?

At least 60 per cent of all crackers are imported from the Far East, and almost all the novelties inside are made in the region. The poor wages and conditions in such places are well documented, but many of the crackers made in this country are assembled by home-workers, a largely female workforce whose plight was highlighted in an Oxfam report earlier this year. The report claims that many home-workers are paid per item produced, resulting in some earning as little as 73p an hour. The report states: "Usually, employers overestimate the speed of the worker, which means that not only are they not paid the minimum wage, but they often [work] long hours to complete the job." You can buy ethically sourced crackers from Oxfam and other charity shops.

How an idea caught fire

Peter Kimpton, a former employee of the Tom Smith cracker company and author of Tom Smith's Crackers, an Illustrated History, claims that Smith was searching for his big idea when he threw a log onto his fire and was immediately inspired by the resulting crackles. It apparently took two years of experiments to develop the snap - two pieces of card whose ends were coated with a small amount of explosive material and bound together. When the strips were pulled apart, the friction caused the material to ignite. Smith used saltpetre, but today manufacturers use silver formulate. The date the first crackers were sold is unclear, but by the early 1860s they were being marketed as "Bangs of Expectation".

Another addition was the "scrap" - the little cutout glued to the main body of the cracker. Kimpton claims that they derive from German oblaten - ornate printed labels for cakes and sweetmeats. The Victorians became fascinated with collecting them - hence the term "scrapbook."

Smith's idea caught the public's imagination. Competitors sprung up, and within a year a bewildering variety were being sold: there were crackers in honour of the Empire, crackers for children and even crackers to commemorate the first plans for a Channel tunnel in the 1930s. Despite this variety, they all contained the same basic elements: a rhyme, a motto or joke, a novelty and, eventually, a hat.

Smith's is now part of Napier Industries, the firm that still makes Tom Smith's Crackers for the Royal Family at its Nottingham factory. Its royal charter was granted in 1910, and the company still has a sizeable chunk of Britain's £120m-a-year cracker industry. Every person in the UK pulls an average of two each year - that's around 120 million in total.

Do the cracker companies keep someone in a room writing jokes?

No. Like most jokes, the ones in crackers are old, endlessly recycled and only occasionally replenished. In Tom Smith's heyday, romantic rhymes penned by established writers were very popular. This is from the firm's "Kissing Crackers - The Sweetest of Christmas Bon-Bons", sold in 1875: "Jack O'Dandy, show yourself handy/ At something sweeter than sugar candy/ You are not often guilty of very great folly/ Go you MUST, snatch a kiss from pretty Polly."

Jokes began to appear in the early 20th century. Typical examples now include: "What do solicitors wear to work? Law suits." And: "Why did the banana go out with the prune? Because it couldn't find a date."

Crackers aren't just for Christmas though, are they?

No. Crackers were produced to mark events like the Paris Exhibition of 1900 and the end of the First World War, and were also marketed for weddings and other social occasions. But they didn't sell well, apart from at Christmas, and made no significant impression outside Britain, and some parts of the Empire. The fashion for knallbonbons ("banging sweets") appears to have diminished in Germany.

So, what else do we need to know about crackers?

During the Second World War, Tom Smith's firm was commissioned to make bundles of snaps that were then used to accustom novice soldiers to the sound of gunfire. The record for the world's longest cracker is held by the children and parents of Ley Hill School in Chesham, Buckinghamshire, who made and pulled a cracker 63.1m long and 4m in diameter in December 2001.

Probably the most expensive around are the Romanov crackers at Fortnum and Mason, which cost £1,000 for six. Gifts include a leather humidor and a set of coffee cups. In 2000, Asprey and Garrard, the jewellers, put a solid silver cracker on sale for £2,995, which came without a joke or hat.

Madonna reportedly makes her own. Instructions on how to do likewise can be found at www.hunkinsexperiments.com/pages/crackers.htm

'Tom Smith's Crackers, an Illustrated History', Tempus, £12.99