Cooking with insects

Friday 25th March 2016

Ever since I was a kid, people have touted insects as the future of food. In some parts of the world they already are - I lost count of the number of times we saw various insects in markets in SE Asia, including this delicious sight in Skoun, Cambodia, where fried spiders are the local delicacy. No, I didn't try them.

You're eating insects

Even westerners eat a surprising amount of insects every year. The FDA's Defect Levels Handbook details exactly how many insect fragments is too many:

  • chocolate - over 60 insect fragments per 100g
  • curry - over 100 insect fragments per 25g
  • macaroni - over 225 insect fragments per 225g
  • wheat flour - over 75 insect fragments per 50g


Cricket flour

But from an environmental point of view, we should all be eating insects. It takes something like 4,000L of water to make a kilo of beef, but just 2L of water to make kilo of cricket flour as well as massively lower methane emissions.

So when a wonderful friend, Celia, was kind enough to give me a bag of cricket flour, I thought I'd give it a go. The 100g bag she gave me contains around a thousand milled crickets. By weight it has twice as much protein as beef, the same amount of calcium as milk, and as much vitamin B12 as salmon.

I tried some of the flour raw, it doesn't really taste of anything. I grew up with a lot of lizards that ate crickets, so I'm very familiar with the smell of them. Unsurprisingly the flour smells just like crickets, slightly nutty and not at all unpleasant.

Here's my recipe for cricket ginger nuts:


Makes 30

  • 170g plain wheat flour
  • 80g cricket flour
  • ½ tsp bicarbonate of soda
  • 1 tbsp ground ginger
  • ½ tsp mixed spice
  • 125g unsalted butter
  • 185g soft brown sugar
  • 60ml boiling water
  • 1 tbsp golden syrup

Here are the finished item - for comparison I made a batch on the left which use just wheat flour, and the cricket cookies on the right.


Preheat the oven to 180ºC / 160ºC fan.

Sift the wheat flour, cricket flour, bicarbonate of soda, ginger and spice into a bowl.

You may want to sift the cricket flour last and keep an eye out for large fragments like this one, which is about 3mm across. Discard them if you're a bit squeamish.

Add the butter and sugar, and rub together with your fingertips until the mixture resembles fine breadcrumbs.

Pour the boiling water into a small jug and add the golden syrup.

Stir until mixed, and then add to the flour mixture. Stir with a knife until the ingredients are all mixed.

The mixture will be very wet and sticky.

Form into small balls and place on a couple of greased baking trays.

Bake in the oven for about 15 mins. They'll be very dark, so don't rely on being able to tell visually when they're cooked or you might burn them.

Place on wire racks to cool, and them film your friends eating them.



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Making a ring

Friday 18th March 2016

I recently caught up with a good friend, Vicky, who rivals me in terms of how many different hobbies she has. Her kitchen worktop was covered in jewellery making tools, and she asked if I wanted to learn how to make a simple copper ring. Of course I did!

1. We started off with a reel of 2mm copper wire. Vicky says it works with anything from 1.5mm up to 3mm

2. The wire was bent around a metal mandrel (nice word) to a size slightly larger than the finished ring

3. We cut the wire to make a hoop

4. And then bent it using special plastic pliers to make the ends of the hoop line up


5. Next we got some jewellery solder

6. And smeared it across the ends of the hoop

7. The ring was then placed on a fireproof block

8. And heated gently until the solder flowed across the joint and sealed it.


9. We cooled the rings down in water

10. And then placed them in a solution of vinegar and salt pickle to remove the oxidised copper

11. The rings were washed in water again and the black cupric oxide rubbed off with a finger

12. Leaving just the rather beautiful red cuprous oxide


13. The rings were then put back onto the mandrell and hammered to be round and the correct size. Sadly this knocked off most of the cuprous oxide.

14. They were then polished using an impressive array of different grades of sandpaper

15. Ta da!



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Friday 11th March 2016

Lock picking has been on my list of skills to learn for years, but I just discovered how easy it is to buy picks on the web. Check out this short video that I made about it.

Here are some links to the picks and locks in the video:

It's really made me realise how poor padlocks are at security. The last lock in the video was used for several years to secure about £10,000 of film club equipment, but I can open it in under a minute without any fuss.

If you're interested in learning this I'll happily lend you my picks, but I'd be careful where you take them. Once forum post I read said that the police in the UK take a pretty dim view of people out on the street with a set of picks. You'd need a pretty good reason to have them, otherwise you're probably going to get arrested.

While learning to pick locks, I've seen a lot of information about locksport - competitive lock opening. There's a really big community in the UK, and their core message, which I've seen over and over is that you can only pick locks that you own, and never pick a lock that's in use. The second one is really important - a couple of times I've broken locks while picking them, and you wouldn't want to do that to your front door!



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Home made spectroscope

Friday 4th March 2016

Pretty much everything we can observe about the universe comes from the light we can see from stars. I've been doing an Astronomy course over the last year and I've come to realise just how much information can be obtained from light!

One thing that's really impressed me is how it's possible to find out all kinds of things about the composition of a star from looking at its spectrum. For example helium was observed on the Sun before it was discovered on Earth.

For a few quid I bought some diffraction gratings which smear out an object's light into a wide spectrum. 

Making a spectroscope

Apart from the diffraction grating, it's all simple stuff. I bought ten gratings from Amazon for £3 if you'd like me to post you one, and I also have some spare razor blades.

You'll need:

  • Black electrical tape
  • Cardboard
  • A long cardboard tube, about 10cm diameter
  • A razor blade
  • A 500 lines/mm diffraction grating

We need to block out almost all the light except for a very thin slit at one end of the tube. This makes for clearer lines in the image.

First of all, cut a circle of carboard that's about the same size as the tube diameter. Cut a rectangle from the middle of the circle that the razor blade will cover. Now carefully break the razor blade in two (obviously it's very sharp) and tape one part to each side of the circle, making sure the sharp bit of the blade protrudes from the semi-circle, like the top right image below.

Now tape the blades onto the card leaving about a 1mm gap between the two halves of the razor blade - like the bottom left image below. A smaller gap gives a clearer image, but needs more light to show a spectrum. 1mm seems to work for me.

Now tape the disc to one end of the cardboard tube, making sure that you still have a 1mm gap when you've finished. When you're done it should look like the bottom right image below. You can check it's okay by looking down the other end of the tube and you should see a very thin slit of light.

Now you need to attach the diffraction grating to the other end of the tube, like this. Make sure that the grating is mounted in the same orientation as the slit, that is when the slit is vertical, the text on the grating is the right way up.

The easiest way to do this is to hold the tube up to a CFL-type bulb in your home and place the grating at one end.

Rotate it around until you can see clear lines in the spectrum - if it's the wrong way round you'll just see a single unbroken line spectrum.

Have a play with it and you'll see what I mean.

Once you've got it in the right orientation, tape the grating to the other end of the tube and you're done! Yes, I taped this one upside down.


So what am I looking at?

Good question. White light isn't one colour, it's a bunch of different wavelengths. When you look through the diffraction grating at a light source, you'll see rainbows off to either side of the slit. The grating spreads the light out into different wavelengths like a prism.

At the blue end (normally depicted on the left, but you might have yours upside down!) is light with a wavelength of 390nm, and at the red end most people can see up to about 700nm. Most lights produce radiation beyond these wavelengths, but you can't see into the ultraviolet or infra-red so it just looks black.

Different light sources display very different spectra. I took some rather beautiful photos so you can see what it looks like.


Incandescent lights

Old school incandescent tungsten bulbs, and halogen lights, produce their light by becoming incredibly hot and emitting radiation as visible light. When you look through a spectroscope at one of these lights, you see a continuous spectrum of light like this:

These kind of lights actually emit more radiation in the infra-red than in the visible part of the spectrum, but my camera and your eyes can't see this, so the red just fades out as the wavelength gets longer on the right side. This is why these lights are really inefficient and also why they're really hot to touch.


Compact fluorescent light

About a decade ago everyone switched to compact fluorescent light (CFL) bulbs in their homes. These bulbs work in a totally different way to incandescent lights. They contain mercury atoms which emit energy in the ultraviolet. We can't see ultraviolet so the inside of the tube is coated in phosphors using various metals including europium and terbium which absorb the UV energy and re-emit it at very specific visible wavelengths.

The mixture is chosen carefully to give a particular colour of light which is how you get warm, cool and daylight CFL bulbs. But unlike incandescent bulbs, they only give off a very specific set of wavelengths of light, as you can see above.  With the help of my good friend Wikipedia, you can identify exactly which atoms are emitting which parts of the spectrum shown.

Mercury's pretty toxic so we'd ideally like to move away from CFLs over time. And also as you can see, the light isn't actually that good compared to incandescent bulbs, which is why a lot of people don't like them very much.



Enter the Light Emitting Diode. These are lower power still than CFL bulbs, and their spectrum is much more like tungsten bulbs.

Don't be fooled though, LEDs also only emit a very narrow set of wavelengths (I'm not sure I fully understand why) so they are also covered in a layer of phosphors. Most household LED lights gives off a blue light which the phosphors absorb and re-emit as other colours.

Because the mix of phosphors is so clever it gives the appearance of a full spectrum, but you can see a dip in the blue part of the spectrum, and less at the red end than an incandescent light.

The horizontal stripes in the image are due to the shape of the LED torch that I used. Good LEDs produce a very nice colour, use a tiny amount of energy and last a really long time. I'm gradually moving all our lights over to LEDs, starting with the halogen bulbs.



You'd think that the cleanest, most complete spectrum would be sunlight, but that's not the case. The inside of the sun is rather hot, and so it radiates light as a broad spectrum. But as the light passes through the outer parts of the sun, and through the Earth's atmosphere, cooler atoms absorb specific wavelengths of light and the resulting spectrum has characteristic dark bands, which you can clearly see in the image below.

These are called Fraunhofer lines after the person who discovered them, and each one is caused by a specific atom. This is how we know the composition of the Sun, and also how helium was discovered - absorption lines were seen in the Sun's spectrum that didn't correspond to any elements that scientists knew about on the Earth.



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