Hi
This is Rajiv, from India.
I have a question - Which colour hat - Black or white - is better to
beat the heat and sun?? Especially when you are in agricultural fields
for hours at a stretch...

Sounds silly, right?

Common knowledge says, white, but I distinctly remember reading
somewhere, where, I forget...that wearing black may not be a bad idea
after all since it radiates heat faster than white does...

Any information you guys can share on this will be welcomed....

Regards,

L.N. Rajiv
Director
Apparel Design & Distribution Unlimted
+91-40-55538149
www.addu.in

In article .com,
"Rajiv India" writes:
|
| This is Rajiv, from India.
| I have a question - Which colour hat - Black or white - is better to
| beat the heat and sun?? Especially when you are in agricultural fields
| for hours at a stretch...
|
| Sounds silly, right?
|
| Common knowledge says, white, but I distinctly remember reading
| somewhere, where, I forget...that wearing black may not be a bad idea
| after all since it radiates heat faster than white does...
|
| Any information you guys can share on this will be welcomed....

It depends whether the temperature of your head is higher than that
of the objects radiating at it. While there ARE circumstances when
black is better, they are so rare as to be ignorable - and, in all
cases when there is significant sunlight, black is always worse.

White. More importantly, it should be porous to water vapour, as
sweating is the primary mechanism for keeping the brain cool.


Regards,
Nick Maclaren.

The message .com
from "Rajiv India" contains these words:

Hi
This is Rajiv, from India.
I have a question - Which colour hat - Black or white - is better to
beat the heat and sun?? Especially when you are in agricultural fields
for hours at a stretch...

Sounds silly, right?

Having tried and tested many sunhats, no it doesn't!

The best I ever had, was lined (crown and brim) with dark green
material. It suffered a fatal injury in Australia. Currently, I have a
white one (cricket style, lined dark green) and a grey-green "French
Legionnaire" style one which claims to be lined with some kind of
UV-reflective material and gives good shade to the eyes and back of the
neck while I'm bent forward gardening.. The greygreen one is definitely
cooler.

Janet.

On 3 May 2006 10:48:12 GMT, (Nick Maclaren) wrote:


In article .com,
"Rajiv India" writes:
|
| This is Rajiv, from India.
| I have a question - Which colour hat - Black or white - is better to
| beat the heat and sun?? Especially when you are in agricultural fields
| for hours at a stretch...
|
| Sounds silly, right?
|
| Common knowledge says, white, but I distinctly remember reading
| somewhere, where, I forget...that wearing black may not be a bad idea
| after all since it radiates heat faster than white does...
|
| Any information you guys can share on this will be welcomed....

It depends whether the temperature of your head is higher than that
of the objects radiating at it. While there ARE circumstances when
black is better, they are so rare as to be ignorable - and, in all
cases when there is significant sunlight, black is always worse.

But don't many desert Arabs (?Bedouin) wear black? Or have I just been
watching too many telly ads!

White. More importantly, it should be porous to water vapour, as
sweating is the primary mechanism for keeping the brain cool.


Regards,
Nick Maclaren.




--
Chris

E-mail: christopher[dot]hogg[at]virgin[dot]net

In article ,
Chris Hogg writes:
|
| But don't many desert Arabs (?Bedouin) wear black? Or have I just been
| watching too many telly ads!

Yes, but that is a social matter, and I believe fairly recent. Read
the Seven Pillars of Wisdom for older information on that.


Regards,
Nick Maclaren.

Nick Maclaren wrote:
White. More importantly, it should be porous to water vapour, as
sweating is the primary mechanism for keeping the brain cool.

But it's not simply perspiration from the scalp that cools
the head, is it. Leaving one ankle, wrist or whatnot(!)
uncovered would do just the same job.

In article ,
Chris Bacon writes:
|
| White. More importantly, it should be porous to water vapour, as
| sweating is the primary mechanism for keeping the brain cool.
|
| But it's not simply perspiration from the scalp that cools
| the head, is it. Leaving one ankle, wrist or whatnot(!)
| uncovered would do just the same job.

No, it wouldn't. The human brain is such a heat source, and so sensitive
to overheating, that there is a lot of specialist blood flow to the
scalp and even through the skull. You remark applies to the rest of
the body, but only partially to the head.


Regards,
Nick Maclaren.

The message
from Chris Bacon contains these words:

Nick Maclaren wrote:
White. More importantly, it should be porous to water vapour, as
sweating is the primary mechanism for keeping the brain cool.

But it's not simply perspiration from the scalp that cools
the head, is it. Leaving one ankle, wrist or whatnot(!)
uncovered would do just the same job.

You emit heat faster from the head than anywhere else except the
trunk. That's why premature babies in incubators wear hats, and
rescuers cover the head of someone who has hypothermia.

Janet.

Nick Maclaren wrote:
Chris Bacon writes:
| White. More importantly, it should be porous to water vapour, as
| sweating is the primary mechanism for keeping the brain cool.
|
| But it's not simply perspiration from the scalp that cools
| the head, is it. Leaving one ankle, wrist or whatnot(!)
| uncovered would do just the same job.

No, it wouldn't. The human brain is such a heat source, and so sensitive
to overheating, that there is a lot of specialist blood flow to the
scalp and even through the skull. You remark applies to the rest of
the body, but only partially to the head.

So if you wear an impermeable lagged membrane over that part
of your head your brain will "overheat"? I don't think so.

Janet Baraclough wrote:
The message from Chris Bacon contains these words:
Nick Maclaren wrote:
White. More importantly, it should be porous to water vapour, as
sweating is the primary mechanism for keeping the brain cool.

But it's not simply perspiration from the scalp that cools
the head, is it. Leaving one ankle, wrist or whatnot(!)
uncovered would do just the same job.

You emit heat faster from the head than anywhere else except the
trunk. That's why premature babies in incubators wear hats, and
rescuers cover the head of someone who has hypothermia.

It still doesn't mean that you'll have a problem caused
by wearing a hat, though.

"Janet Baraclough" wrote in message
...
The message
from Chris Bacon contains these words:

Nick Maclaren wrote:
White. More importantly, it should be porous to water vapour, as
sweating is the primary mechanism for keeping the brain cool.

But it's not simply perspiration from the scalp that cools
the head, is it. Leaving one ankle, wrist or whatnot(!)
uncovered would do just the same job.

You emit heat faster from the head than anywhere else except the
trunk. That's why premature babies in incubators wear hats, and
rescuers cover the head of someone who has hypothermia.

Janet.

That's only because heat rises. I thought the idea of holding a new born
babe upside down by the legs was to prevent heat loss:-)
If this theory is correct then cats and dogs do not have a problem on the
basis that they are roughly horizontal.

The message
from Chris Bacon contains these words:

Janet Baraclough wrote:
The message from Chris Bacon contains these words:
Nick Maclaren wrote:
White. More importantly, it should be porous to water vapour, as
sweating is the primary mechanism for keeping the brain cool.

But it's not simply perspiration from the scalp that cools
the head, is it. Leaving one ankle, wrist or whatnot(!)
uncovered would do just the same job.

You emit heat faster from the head than anywhere else except the
trunk. That's why premature babies in incubators wear hats, and
rescuers cover the head of someone who has hypothermia.

It still doesn't mean that you'll have a problem caused
by wearing a hat, though.

It does mean that leaving your whatnot uncovered will not have a
cooling effect inside your hat.


Janet

In article ,
Chris Bacon writes:
|
| No, it wouldn't. The human brain is such a heat source, and so sensitive
| to overheating, that there is a lot of specialist blood flow to the
| scalp and even through the skull. You remark applies to the rest of
| the body, but only partially to the head.
|
| So if you wear an impermeable lagged membrane over that part
| of your head your brain will "overheat"? I don't think so.

You may not think so, but it is nonetheless true.

Under moderately extreme conditions, people have had brain damage from
wearing protective headgear. The point is that the rest of the body can
take higher temperatures than the brain (in the case of muscle, MUCH
higher) and this means that the absence of specific head-cooling causes
trouble as soon as the average blood temperature approaches the brain's
limit. People exercising hard in hot conditions may have limb blood
temperatures higher than the brain can take.


Regards,
Nick Maclaren.

The message
from "Rupert \(W.Yorkshire\)" contains these words:


"Janet Baraclough" wrote in message
...
The message
from Chris Bacon contains these words:

Nick Maclaren wrote:
White. More importantly, it should be porous to water vapour, as
sweating is the primary mechanism for keeping the brain cool.

But it's not simply perspiration from the scalp that cools
the head, is it. Leaving one ankle, wrist or whatnot(!)
uncovered would do just the same job.

You emit heat faster from the head than anywhere else except the
trunk. That's why premature babies in incubators wear hats, and
rescuers cover the head of someone who has hypothermia.

Janet.

That's only because heat rises.

The insulation afforded by a beard overheats the head to a dangerous
degree, Rupert, as you have probably forgotten by now. This is why
bearded men usually go as bald as coots, as nature tries to compensate.

I thought the idea of holding a new born
babe upside down by the legs was to prevent heat loss:-)
If this theory is correct then cats and dogs do not have a problem on the
basis that they are roughly horizontal.

Cats and dogs mainly sweat through their feet. That's why they aren't
allowed to weat trainers.

Janet

Nick Maclaren wrote:
Chris Bacon writes:
| The human brain is such a heat source, and so sensitive
| to overheating, that there is a lot of specialist blood flow to the
| scalp and even through the skull. You remark applies to the rest of
| the body, but only partially to the head.
|
| So if you wear an impermeable lagged membrane over that part
| of your head your brain will "overheat"? I don't think so.

You may not think so, but it is nonetheless true.

Under moderately extreme conditions, people have had brain damage from
wearing protective headgear.

I'd like to see reference material.

The point is that the rest of the body can
take higher temperatures than the brain (in the case of muscle, MUCH
higher)

Yes, of course...

and this means that the absence of specific head-cooling causes
trouble as soon as the average blood temperature approaches the brain's
limit.

That does not follow. You could have someone exercising very hard indeed
in a cold environment, and I bet you they would not get heatstroke from
wearing a hat.


People exercising hard in hot conditions may have limb blood
temperatures higher than the brain can take.

True enough. It does not mean that their brain will overheat, though.


You've strung together a *lot* of wriggly words there. Stick to
non-extreme gardening, and wear a hat.