The chemistry of Christmas crackers

Christmas has now just about finished for another year and I’m sure at some point over the festive period we all ate too much, drank too much and of course pulled a few Christmas crackers. Despite wondering if you’ll get a mini tape measure or tiny pack of cards, I doubt you’ve ever put much thought into what’s in a cracker. The distinctive bang comes from silver fulminate, AgCNO. Fulimates contain the fulimate ion, CNOand are referred to as friction explosives. This is what makes them perfect for crackers, as they produce the distinctive bang, a tiny explosion, when pulled. The silver fulminate is coated on a piece of card, this runs next to another piece of card which is abrasive- a bit like sandpaper. When the cracker is pulled the two bits of card are pulled apart, rubbing together, creating friction and igniting the silver fulminate. The tube around this amplifies the sound making it louder. Apart from its use here in Christmas crackers silver fulminate has very few other uses, it is extremely explosive and sensitive, so much so that a few grams would self detonate due to the force of its own weight.

I hope you had a cracking Christmas and a great new year!



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