Naked Science Forum
General Science => General Science => Topic started by: paul.fr on 19/11/2007 08:07:21
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I know they have the word thermal in their title, but how do thermal underwear and pyjamas keep you warm? Also, why do waterproof leggings make you feel cold?
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They are just good insulators. Also, the fact that they 'hug' your body means there are no channels for cool air to circulate 'next the skin'.
Modern thermals have other features like the ability to 'wick' the sweat away. This avoids cold damp patches, although you still lose the same amount of heat through evaporation. (You can't avoid the latent heat of vaporisation)
My waterproof leggings don't make my legs cold because I paid enough money from them. They have a nice 'taffeta' lining which keeps the cool surface away from my legs. I am always amazed at the sensation when I put on my goretex leggings; it actually feels 'dry' down there. I must have humidity sensors on my legs!
I should imagine it's the layer of condensation inside plastic leggings which gets cold and then slaps against your leg -horrrrrid!
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Long underwear
From Wikipedia, the free encyclopedia
http://en.wikipedia.org/wiki/Thermal_underwear
Long underwear, often called long johns, is a style of two-piece underwear with long sleeves and long pantlegs that is normally worn during cold weather.
Modern long underwear has largely supplanted the traditional union suit. It is usually made from fabric with a box-weave texture, although some varieties are also made from flannel.
The type known as "thermal underwear" is made from two-ply fabric, which uses trapped body heat to insulate against cold air.
Sir Benjamin Thompson, Count Rumford has been credited with inventing thermal underwear.
The two-piece design is credited to Truro, Nova Scotia-native Frank Stanfield of Stanfield's Limited on 7 December 1915.
[edit] Etymology
According to Michael Quinion,[1] "John" may be a reference to boxer John L. Sullivan, who was known to wear a similar garment in the ring. However, this explanation is uncertain and the word's origin is ultimately unknown.
Many Nova Scotians credit the term "Long Johns" to John Stanfield. Son of Charles Stanfield, brother of Frank Stanfield, and co-founder of Stanfield's Limited located in Truro, Nova Scotia, Canada.
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Maybe the waterproof leggings have more rubber or something and don't hold the heat so good.. I don't know a guess!
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waterproof trousers are generally very thin so don't insulate very well by themselves, but if worn over the top of something thicker, they stop the wind so can hugely increase the effectiveness of thermals.
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That makes pretty good sense!
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I'd trade my hubby for a pair of long johns! It's freezing here!
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What you need is a wooly sheepskin warmer Carolyn
(sorry Neil!)
I don't know about goretex. My hubby swears by them and their hi-tech abilities but I just really don't like them. I don't find them comfortable somehow and still preferr natural materials like e.g. brushed cotton/silk/wool mixes in thermals.
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carolyn it's supposed to be sixty tomorrow here
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The effectiveness of Goretex may depend on the wearer. It needs a 'significant climate difference' between the inside and the outside to achieve the effect of pumping water out**. I get really hot and that may be why it works for me. If you are a 'cool' person, Alandriel, it may not shift the damp so well for you.
**The Goretex Tent idea didn't last long because, it was claimed, there was too little temperature difference across the fabric.
BTW, Is that 60 CELCIUS????? or someone's age?
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no no farenheit
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Phew - what a relief
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lol. i'd put both on here but i can't ever remember how to figure out celsius. i knew how for the test in the fifth grade... haven't used it much since then
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°C to °F Multiply by 9, then divide by 5, then add 32
°F to °C Deduct 32, then multiply by 5, then divide by 9
but, lazy as I can be I preferr to use one of the many online calculators [;D]
Sophie: that's interesting! And your speculation is quite right. I (apparently) am much more of a cool person than a hot person. I never suffered much from the heat in Egypt but feel perpetually frozen over here in the UK. Hubby on the other hand is a walking nuclear reactor LOL
Different metabolisms I guess?
Though, then again, my doc says I have a fast metabolism so that's probably not the case then....
.... heheh.... yet another mystery perhaps worth a thread [;D]