Down: The Science of The Ultimate Insulator

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Mountain Equipment Vega Jacket, 3 kbNothing beats down insulation. Despite decades of synthetic material development we still can't match the stuff that geese and ducks wear. So what makes down so good, and why can't we recreate it? Scientist Matt Fuller takes a close-up view

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 jsmcfarland 11 Jun 2016
In reply to UKC/UKH Articles:

This was really, really, really interesting. Great article!
 benman 11 Jun 2016
Great article Matt, every day is a school day! Love the microscopic imagery.
 James Rushforth Global Crag Moderator 11 Jun 2016
In reply to UKC/UKH Articles:

Great and really interesting article.
In reply to UKC/UKH Articles:

More of this kind of thing.
In reply to planetmarshall:

Steady now...
In reply to UKC/UKH Articles:

Terrific - great text and great pics. But "Basically nature thought long and hard about this" - please tell me you're not an Intelligent Design fan!
 Mr Fuller 12 Jun 2016
Thanks for the positive comments all.

In reply to stevesmith:

No, not in the slightest! That was me anthropomorphising nature somewhat. I could - and perhaps should - have said that evolution has perfected it.
brora boyan 12 Jun 2016
In reply to UKC/UKH Articles:

Does it make much difference to the feathers when the bird is being plucked alive or dead?
 Mr Fuller 13 Jun 2016
In reply to brora boyan:

This wasn't something I investigated, but I'd be very surprised if down's chemical or physical properties were changed by the bird being alive or dead at the time the down were harvested.

However, there is more to down than just chemical and physical properties, and harvesting from live birds would change the down's provenance in a way that most people would find highly unpleasant.
In reply to Mr Fuller:
Nice article.
Just a question about the statement:"and the barbules (even finer fibres that grow like twigs off the barbs) are a nearly-perfect diameter to block heat transfer by radiation."
I thought that radiated heat was only a small proportion of heat loss from the body. Also would the down's properties be much more likely to decrease the heat lost by convection and conduction rather than radiation?
 Mr Fuller 30 Jun 2016
In reply to oldie:

Thanks. The body actually radiates a lot of heat. If you stood naked in a field on a cool day with no wind, more than half of your heat would be lost by radiation. The key to blocking heat loss is putting solid objects in the way, and that's one of the things that down does very well: there is almost zero heat loss by radiation through a thick load of down.

Down blocks all the heat loss mechanisms very well, and that's why it is so effective. There is no natural convection inside a load of down because the air gaps are too small, and forced convection (e.g. wind) is usually minimal because of face fabrics over the sleeping bag or jacket. Conduction is where thickness is important, and obviously down-filled things tend to be really thick, minimising heat losses by conduction.

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