One of the most time consuming things about  filming outdoors is the walking shot. Speaking to camera interview style is mostly achieved easily after just a few takes. But the seemingly trivial and non-technical activity of filming me walking takes an inordinate amount of time. Yes, walking. From all angles and directions. Walking into shot, walking out, walking in for a close-up and then again in wide angle. Close-ups of my boots crunching on loose rock – this is a particular Director’s favourite, much loved also by the sound man.

The odd thing about it is that while in everyday life walking is achieved without thought, in front of  camera  one becomes embarrassingly self conscious. It is disconcerting  to feel scrutinised just for putting one foot in front of another.   In my experience the 80:20 rule applies  – 20% talking, 80% walking. Perhaps they are trying to tell me something?

In front of Pico Viejo

I’m in Tenerife, filming with Pioneer Productions for a documentary about volcanoes and their effects on Earth’s climate. After an early start in front of Pico Viejo  (above)  we moved into the centre of the Las Canadas Caldera.  The highlight of the day was a piece explaining the effect magma viscosity has on volcanic behaviour. To show this we brought from the UK two big glass test tubes. The idea was to fill one with syrup and the other with a mix of syrup and sugar. Syrup only represents lower viscosity magma, syrup+sugar higher viscosity. The clever bit is then to pump gas into the base of both tubes to see how each fluid responds. The object is to film bubbles rising passively through the thin syrup while the thick mixture traps the gas, pressure builds and the whole lot ‘erupts’ violently

Mount St Helens erupting in 1980.

(cue cut away to your favourite archive clip of Mt St Helens/Pinatubo/Montserrat in explosive mode).

Well at least that’s the theory. The first problem was getting a high enough gas pressure to actually make bubbles. The butane gas bottle we started with was regulated at a feeble 28 millibars. When attached to the base of the syrup filled tubes nothing happened. We would have been better off blowing into it through straws.

Every shoot on location hires someone called a fixer. Always a local, their job is to sort stuff like this. So the challenge was on: fixer, get us a massive canister of gas ( don’t care what) without a regulator,  and do it by lunchtime. Two hours later a  steel canister of helium gas appeared on a trolly. With an unregulated nozzle. We didn’t ask where he got it but it sure did the trick. Then disaster struck. One of the plugs holding in the syrup came out and the stuff oozed everywhere.

Sticky mess.

The weight of the syrup in the tube was too much. Off again down the mountain to get more syrup. Time is now running out – we need to get the last cable car up Teide at 16.00 and it’s now 14.30 with nothing in the can to show for our efforts. But all’s well that ends well. After much hilarity, we get the shot and make the cable car with seconds to spare. Lovely.

But if you happen to see a man lugging a half empty syrup soaked, sand encrusted canister of helium gas down the slopes of Mt Teide, give him a wide berth. His next fixing job is for Vogue magazine, and he needs to scrub up quick.

Teide at sunset.