Saturday, 30 September 2006

S103: Potatoes have feelings too.

Your mission, should you decide to accept it, find out the water content by percentage weight of your average potato. This is a block one experiment.


After some time spent reading through the book, it was interesting to have a break and start some practical skills. Lets see, by heating the potato in the microwave, we can drive off all the water held in its cells, and see how much of it there is.

Now - what equipment do we need.
  • A microwave - check!
  • A potato or two - check (Maris Piper, unpeeled, 3).
  • A calculator - check
  • Scales - check (digital ones, weighing in 5g increments - wooooh!)
  • Notebook - check
  • 5 year old helper - hmm, not mentioned in the notes.


First job, find a suitable plate. I decide I want a lightweight one so that it won't affect the scales too much. If the plate weighed 10 kg, the scales probably wouldn't be very sensitive to a few grams change in weight.

Now - slice up the potato, and already my helpers attention had started to wander. I wanted to slice them thin for speed, but decided I just needed to get on with it while the attention was focused on him trying to switch on the calculator.

Right - so into the nuke and blast for the first 4 mins. Out it comes, and its a little warm. We measure the weight, and I write down my first figures. I return the potatoes to the oven, while my helper tries to weigh his hand.
After a little bit of dissuasion, he's back on the calculator, now having got it switched on. So I ask him to type in the numbers whilst doing the arithmetic in my head as a double check. We have a few false starts...

By now the next 4 mins is up, so I do another weighing. I hear the calculator clatter to the floor.
Anyway, another weight recorded, and back to the oven. I turn around, and there he is is, trying to weigh his head this time, and read the numbers at the same time.

We do some more calculator work, and then he wants to know why crocodiles and caimans don't both live in the amazon.

The microwave peeps, and the calculator clatters to the floor. Another measurement, and my helper is getting quite good at subtraction. I manage to persuade him that weighing other parts of his body is really not worth it.

The next record and the calculations are definitely wrong, where we'd been subtracting 55g, he now wants to see just how many 5's he can get on the display. I think I've just found a new source of errors...

We're down to two minutes between bursts now, and there is barely time to drop the calculator and recover it between the measurements, but he rises to the challenge majestically.

The potatoes are now looking distinctly crisp shaped, and are very hot when trying to separate them.

Another couple of blasts, and there is no change in measurement, so I pronounce it done. The calculator clatters to the floor one last time in celebration.


A bit of calculation, and I come up with a figure of very slightly over 80% for the water content.

I reflect upon the geniuses whose shoulders I am standing on, Newton, Galileo, Darwin, Einstein. I wonder if they'd have seen further with a little helper?

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