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Why does Wool keep you warm and dry ?

Well it all seems a bit obvious when you think about it….

Sheep roam about outside in the wet and the cold – and manage to survive quite comfortably.  As all they are wearing is a thick woolly coat it stands to reason that wool must keep them warm and dry.

But when you think about it again – sheep don’t have the option to slip off their coat when it warms up a bit (well at least not until we shear it off).  But they still manage to keep cool and dry in their woolly coat.

Exactly the same logic can be applied to us, when we wear clothing made from wool.  When it is cold – wool garments will help keep you warm, when it is hot wool can help you keep cool.  This makes it ideal for use in thermal underwear.

But why exactly does it work like that….

There are three really important features of the wool fibre that contribute to this;

1.  Wool has a natural “crimp” which creates air pockets

2. Wool will “wick” moisture away from the skin

3.  Wool can absorb a lot of water without feeling wet.


The “crimp”


Wool fibres have a natural crimp or curl which means that the fibres do not lie flat against each other,  but are curled up.  This creates tiny pockets of air which form an insulating layer, this insulation will either keep out heat or cold.  Think of a thermos flask – it will keep a cold drink cold, or a hot drink hot – wool works in a similar way.




The wool fibre is naturally “hygroscopic” – this means it has the tendency to attract and hold moisture from the surrounding environment.  In thermal underwear terms – this means that wool will draw (or “wick”) perspiration and moisture away from your skin – keeping you amazingly dry.  Keeping dry will also help keep you warm.


Water absorbtion


Wool can absorb up to 30% of its weight in moisture before it begins to feel wet.  This gives it an amazing ability to keep you dry and warm – it also prevents overheating when you are exercising hard.  So it will wick the moisture away, AND it will not lose its thermal insulation properties – a great combination, when looking at thermal underwear.


As a final benefit wool is also resistant to mould and mildew – making it more odour resistant than many fibres.  So next time you look at a herd of sheep sitting in a field you should think about how clever that woolly coat really is !