Thursday, 24 May 2012

Can you cook popcorn with a magnifying glass?

Well, amazingly, the short answer is YES — but, it's all about the method.

A regular magnifying glass is able to set fire to a popcorn kernel quite easily.  This however is not what we want.  We need the moisture inside to boil, cook the starch and then burst the shell explosively.

We used a larger magnifying lens — a flat 'fresnel' book magnifier — and sat the kernels in some cooking oil in a teaspoon.  I think the cooking oil is there just to spread the heat around the kernel rather any cunning cooking chemistry.  After a while it will start bubbling (some of it's moisture boiling off) then after a while longer, if you're lucky, it'll explode.  We managed to get a good few of them to pop but only one made a lovely big popcorn — the others were kinda half-hearted attempts at popping.

Focussing the sunlight too tightly on the kernel lead to burning.  A loose focus on the teaspoon head spread the energy out to a more controllable level.

After all this discovery we went inside and hit the stove with a saucepan.  They all popped in no time.  It just goes to show how much energy your stove kicks out!

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