How can I get fleas out of my hat?

04 July 2013



Hi, I'm Fred Richardson, an ex-pat from Manchester living in the NT since 1973 and Alice Springs since 1992.

I was introduced to you guys via ABC Radio National - Robin Williams The Science Show last year and have been podding and streaming you ever since. The delivery is lovely and the content just a great mix across the science arena.

Okay, so it happens occasionally that I get fleas brought into the house via a cat. Invariably some they end up in my woollen bob cap.

I tried to microwave some away with no luck, so can you tell me what size an insect [water and protein bag] would have to be for a microwave to boil it?

I've wet the bob cap and waved it, but it more or less destroyed the cap.

So, can suggest and safe mechanism, a form of box say that I put my hat in, that would somehow guide or jiggle the microwaves around to be an effective de-infestation against tiny fleas?

And synchrotrons, I'm not sure I understand properly what causes the accelerated electrons to emit photons, and how exactly their radiance is put to such a variety of uses, someone said their light is tuneable from infrared to beyond UV, is this what makes them so special.

Thanks, Fred


Chris - I suppose that the reason the fleas escape the microwave - I mean, Mark, you're the physicist, but I'll give you my theory is that the wavelength of the waves in a microwave oven is about 12 centimetres. So, there's quite a big distance, 6 centimetres or so between the peaks and the troughs where the energy is most intense. In other words, the displacement is greatest and therefore, the heating effect is greatest. If you're something tiny like a flea, you can probably fit quite snuggly into the gaps where there are fewer microwaves and therefore, you're not going to get cooked so well and you can also move out the way.

Kat - This is why with a microwave, you have to kind of keep stirring it and it has to go around and there's a lot of conduction of heat going on in the water in your food.

Mark - It sounds right to me, Chris. If you have these hot spots within a microwave that are a few centimetres apart, there's plenty of room for fleas to slip in between those really and survive.

Chris - Dave did an experiment about 6 or 9 months ago on the Naked Scientists where we wanted to see whether microwaving your dishcloth was a good way to sterilise it or clean it rather than have to boil it up on the hob and we found that actually, before it gets clean, it just catches fire because the salts that are in the cloth, owing to having cleaned up dirty surfaces actually end up raising the boiling point of the water there to a very high temperature and they also encourage a very high current to flow in that region. So, it does get very, very hot. So, I suspect that maybe sweat on the cap is doing the same thing and making the cap get hotter before the fleas do and therefore, the cap gets cooked into submission before the flea has a chance to get a deathly dose of microwaves.

Mark - I have to wonder why you would choose to use your microwave to get rid of fleas. Is a no flea powder available?

Kat - I think the only way is, it would be if you immerse.

Chris - Turntable then.

Kat - Yeah, turntable and maybe immerse the whole hat plus fleas in water.

Mark - I think that's right, Kat actually. Put the whole lot in a bowl of water and microwave it and if you heat it enough, that will kill the fleas.


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