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Carriacou Diary: Mike Bullivant

Day 28 — Fireworks

The final challenge: make gunpowderSo 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.

Mike works on the gunpowderOne 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 29 — Fireworks

Mike and Jonathan admire the trajectory of their rocketsWell, 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.

Day 30 — Fireworks

The stage is set for the performanceWe don't have a lot of time left. A bit of experimentation tells us that bamboo stalks/trunks with a diameter of around 8-10cm make pretty good casings for the flares if they're cut to a length of about 30cm. Designing the rocket isn't so easy. It takes four or five failed attempts to produce something that stays up for more than a few seconds. NASA can stop worrying. We reason that a Catherine wheel is little more than a rocket wound in a spiral, so that's the design we go for. But will it work?

An hour from dusk on the third and final day, and we have almost everything ready. All we need to do is set the fireworks in some form of display. An electrically powered detonator plunger that Jonathan's knocked up means we can set them off from a safe distance. At dusk, the Rough Science orchestra (Kate H on tubular bells, Mike L on double bass, and Kathy and Ellen on hard drugs from the look of things) takes its seats for their first and final (thank God) performance. We all have just the one opportunity to get this last shot of the series right — tomorrow we fly back to the UK.

Our firework display, and the accompanying performance of some of the finale to Beethoven's 9th Symphony has to go right first time. I'm confident about the fireworks but I'm not so sure about the musical competence of the orchestra. I've heard them. They've been practising for the last three or four hours and they still sound like a primary school band from Preston. A little bit of German soil has been stirring for much of the afternoon.

A successful firework finaleThe tension mounts as the sun slowly slips below the horizon. In the twilight, the film crews get their final briefing from the director, Sarah. The whole production team is tired. Everyone's exhausted after almost seven weeks of hard work. This is it. The end of the shoot. A sad moment. The sky takes on an ominous bronze glow. The thunder rumbles threateningly in the distance. In the half light, the 'set' we've constructed looks like something out of a Denis Wheatley novel. It's all a bit new-age satanic, what with the fire, the skulls and the pentangles. The kind of thing you come across in the Green Field at Glastonbury. What would Lord Reith make of it?! Is this degree of satanism OK for an 8pm weekday slot? Have we all lost the plot and gone too far up-river? Should I be more worried about this than I appear to be?

So many troubling questions, the most important of which is: will nos sons et nos lumières all come together for the final, explosive take of the series?

Well, you'll just have to tune in and find out, won't you!