Ah, Christmas. That time of year where we exchange presents, eat too much, watch television programmes that we would never watch under any other circumstances, politely listen to relatives we avoid during the rest of the year, and have a nice time playing with gunpowder.
Yes indeed; today we speak of that staple of festive-type seasons all over the place, the Christmas cracker.
When you take apart a Christmas cracker you’ll find the tiny plastic toy version of a thing you’d never want if it was full sized, and the cracker part. The cracker part is what we’re interested in, so put aside the miniature comb and have a closer look.
The cracker is made up of two strips of card, and the end of each strip has gunpowder in it. Gunpowder is made by mixing potassium nitrate (also called saltpetre), charcoal and sulphur; each of these components has a very particular job to do if Auntie Joan is going to get a little bit of a fright when it goes off.
Fire – all fire – needs three things: fuel, oxygen and heat.
The charcoal provides the fuel, as it’s mostly carbon, and as you may have noticed, carbon generally works very well as a fuel source.
Oxygen is supplied very readily by the saltpetre – as it gets heated up, various shenanigans occur within it that release oxygen as a byproduct.
And finally, the heat is provided by the friction of the two strips of card being pulled apart. However, that does not produce nearly enough heat to set off the charcoal and saltpetre – which is where the sulphur comes in. It lowers the temperature necessary for the other two components of the gunpowder to get going.
And then, to everyone’s delight, you have a little explosion.
And, of course, if you had enough of them perhaps you could make an explosion big enough to do something useful…