How do Christmas crackers work?

Christmas crackers are a popular tradition at the Christmas dinner table, but how do they make that loud bang when pulled apart?

Inside the main cardboard tube are two strips of card. One contains a small amount of a chemical compound called silver fulminate (AgCNO), which is made by reacting concentrated nitric acid with silver and ethanol. This compound is very sensitive and can even self-detonate under its own weight in large enough quantities.

The other strip of card is coated in a fine sandpaper which, when the cracker is pulled, creates friction and heats up the silver fulminate on the other strip. This is what creates the explosion and loud bang.

Crackers were invented by baker Tom Smith in 1847. On a trip to Paris he discovered the ‘bon bon’, a sugared almond wrapped in a twist of tissue paper, which he soon began selling in his shop in London. To boost sales he developed them further, first including a love motto in the tissue paper, and then adding an explosive element which was inspired by the crackle of a log as he threw it on his fire.

Eventually he dropped the sweet and the ‘bon bon’ name, added a surprise gift and labelled his new invention Cosaques, which would later simply become the Christmas cracker.

After his death, a drinking fountain commemorating Tom Smith and his wife was erected in Finsbury Square, London by their son Walter.

Find the answer to more baffling questions in How It Works magazine. Order it in print, download the digital version or subscribe today to ensure you never miss an issue!

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