Day 1

On the first day of filming it's up at 6.30am, a shower, breakfast, and a 45-minute drive (northwards along the coast) from where we're staying in Stonetown (aka Zanzibar Town; more later) to our workshop base at Chuini. My challenge for the first programme is to produce iodine from seaweed. None of us knows whether the seaweed around Zanzibar contains enough iodine to be able to extract it in sufficient quantities for our purpose - to purify the drinking water that we'll be taking with us on the boat on Day 3 of this first challenge.

For Ellen and me it's a  four hour return trip in a four-wheel drive to the east coast, where she thinks there's seaweed that will do the trick. We spend an hour or two at low tide trying to harvest enough to take back to base, where I can set to work extracting the iodine.

We're not back at Chuini till well after 2pm, and the rest of the afternoon is spent burning the seaweed to ash over a fire. To get the iodine out, I have to dissolve the ashes in water and filter off anything that doesn't dissolve. At this stage, the iodine is mostly in the form of water-soluble potassium and sodium iodides. Of course, these will be mixed with other inorganic salts that the seaweed has absorbed from the sea. By concentrating the filtrate (the solution that passes through the filter - in our case, cotton wool and muslin cloth), we'll be able to selectively remove some of the inorganic salts that we don't want (a process called fractional crystallisation), and increase our chances of extracting iodine.

We've collected two huge baskets of seaweed, and burning that much to ash takes several hours. The job's made much easier by the fact that I have a helper this afternoon; one of the Zanzibari drivers, Kitende, who's been hired to ferry us from location to location - Hisdory and Hamdani are the other two drivers. Kitende helps out by stoking the fire and starting the filtration process. By the end of a long day, we've reduced most of the seaweed to ash, dissolved the ashes in boiling water, and are well into filtering the resulting aqueous solution. It's been a tiring day working alongside a roaring fire in these temperatures. You sweat buckets. Although I've been allocated a wonderful laboratory space at Chuini, we're working outside in the heat of the sun, because of the smoke from the wood fire, and the somewhat hazardous nature of the Chemistry involved.

We still have a lot to do over the remaining two days. In fact, we effectively only have two and a bit days for this challenge as we spent a long time this morning filming the opening sequences for the first programme, when Kate (Humble) gives us our challenges. The trip to collect the seaweed ate into the day too. It's a good job that this first challenge is a light one.

It has to be said that the Production Team has done an excellent job in kitting our Chuini base out. We seem to have everything we need at the moment, and can always fall back on our reliable, local 'fixer', Eddie, for anything we might subsequently want. It's comforting to hear from the locals that you can get hold of anything on Zanzibar. Over the next few weeks, I'm sure we'll be putting their claim to the test.

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Content last updated: 26/01/2005