Day 1

So this is it, just one more programme to shoot. What's Kate Humble going to give me to do this time? Imagine how I feel when she sets Jonathan and me the task of making some gunpowder for a firework display! This is going to be fun. I'd be surprised to meet any adult professional chemist who hadn't experimented with making her or his own gunpowder in their youth. I certainly had. Of course, it's something that I'd strongly discourage these days. Gunpowder is dangerous and people have lost fingers and worse, their sight, by playing around with it.

One of the three chemicals that we need to make gunpowder we can get from bat droppings in the lime factory and the top-soil from a number of latrines on the island. This particular compound's water-solubility will mean that we can purify it quite easily. As well as being one of the three ingredients of gunpowder, it could also serve as the source of our fuses.

There's no way that we'll be able to get hold of sufficient quantities of the second chemical we need, even though this is a volcanic island. Kate is sporting enough to provide us with a lump of sulphur with which to play. The third component is readily available, so it's just a question of experimenting (very carefully) so as to determine the best composition for our gunpowder mixture. It needs to be just right if our fireworks are to work properly. Jonathan gets on with this while I set my mind to thinking what we can add to the gunpowder to give the fireworks some colour.

Day 2

Well, we've got plenty of sodium chloride, from seawater (this will give a yellow flame when burnt). We could also file down some galvanised (zinc-coated) nails to give us zinc dust (which will give a white sparkler effect). Then there are plenty of cola cans lying around the site, that we could file down to give us aluminium powder. This too will create a shower of white sparks if added to the gunpowder mixture and ignited. Most surprising of all is the fact that the toothpaste I regularly use (and have with me back at the hotel) contains 15% by weight of strontium chloride (it acts as a gentle abrasive, I guess) and I know that some strontium salts give a crimson flame when heated. I need to test if strontium chloride is one of them. Sadly, it isn't, as I find out when I heat a bit of the toothpaste on the end of a hot wire. It gives no coloured flame at all. However, treating the chloride in the toothpaste with a drop of sulphuric acid from the car battery, produces strontium sulphate, which to my relief does give a scarlet flame when heated. We'll make as much of the strontium sulphate as we can, dry it and grind it (carefully) in with the gunpowder.

By the end of day two, Jonathan and I have an impressive collection of different gunpowder mixtures that we're confident will produce a good range of colours when set off (though it'll be far removed from the Sydney Harbour Bridge on Millennium Eve display!). We've also been putting a good deal of thought over the last day or two into the design and construction of our fireworks. We decide to go for a collection of bangers, a rocket, a Catherine wheel and some flares. All we have to do now is make the damn things.

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Content last updated: 21/07/2006