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Message no. 1
From: Paul Gettle <RunnerPaul@*****.COM>
Subject: Re: IR and Glass [was: Camo and Ruthenium]
Date: Sat, 8 Aug 1998 22:47:06 -0400
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At 09:06 PM 8/8/98 -0500, D.Ghost wrote:
>>> Nope. Glass is opaque to IR radiation.
>>Okay, given that heat is a form of IR radiation - why can you get
hot
>>when the sun shines through glass on you then?
>Not sure. It may be a result of other radiation emitted by the sun.
If,
>on a cold day, someone stands out side and holds their hand against
the
>glass and you stand inside with your hand where their hand is, you
feel
>cold glass not the heat from hand.

I think it's just a case of glass only being partially opaque to IR
radiation. The way I picture it, glass is to radiant heat, as items
such as draperies and lampshades and rice paper paneling are to
visible light.

Radiant heat can shine through glass, but only diffusely, and only if
the amount of heat is in a sufficient quantity. The example with hands
on either side of the window, IMO would be a case where the amount of
radiant heat is insufficient. As a counterexample, I would like to
offer a glass-doored fireplace, with the fire lit, and the doors
closed. The radiant heat from the fire in the fireplace can still be
felt.

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--
-- Paul Gettle (RunnerPaul@*****.com)
PGP Fingerprint, Key ID:0x48F3AACD (RSA 1024, created 98/06/26)
C260 94B3 6722 6A25 63F8 0690 9EA2 3344
Message no. 2
From: Tim Serpas <wretch@**.COM>
Subject: Re: IR and Glass [was: Camo and Ruthenium]
Date: Sun, 9 Aug 1998 00:30:52 -0500
Typical window glass is opaque to UV for sure.
Not sure about IR. Maybe you have misremembered?

Wretch
Message no. 3
From: Lady Jestyr <jestyr@*******.DIALIX.COM.AU>
Subject: Re: IR and Glass [was: Camo and Ruthenium]
Date: Sun, 9 Aug 1998 15:37:42 +1000
> Typical window glass is opaque to UV for sure.

Not 100% opaque. Yes, it isn't totally transmissive, which is why for UV
spectroscopy you need to use quartz cuvettes, for instance, but it does
transmit a proportion of incident UV.

Lady Jestyr

- It's not pretty being easy -
| Elle Holmes | jestyr@**********.com | http://jestyr.home.ml.org |
| Shadowrun Webring Ringmaster | GeoCities Leader | RPGA Reviewer |
Message no. 4
From: "Droopy ." <mmanhardt@*****.NET>
Subject: Re: IR and Glass [was: Camo and Ruthenium]
Date: Sun, 9 Aug 1998 17:59:20 -0400
From: Lady Jestyr <jestyr@*******.DIALIX.COM.AU>
Subject: Re: IR and Glass [was: Camo and Ruthenium]

> > Typical window glass is opaque to UV for sure.
>
> Not 100% opaque. Yes, it isn't totally transmissive, which is why for UV
> spectroscopy you need to use quartz cuvettes, for instance, but it does
> transmit a proportion of incident UV.

You can see near IR light and near UV light both through glass,
IIRC (I've used the IR light on night vision goggles as well as a UV
laser sight through a window before.)


--Droopy
Message no. 5
From: bryan.covington@****.COM
Subject: Re: IR and Glass [was: Camo and Ruthenium]
Date: Mon, 10 Aug 1998 09:48:50 -0400
> I think it's just a case of glass only being partially opaque to IR
> radiation. The way I picture it, glass is to radiant heat, as items
> such as draperies and lampshades and rice paper paneling are to
> visible light.
>
> Radiant heat can shine through glass, but only diffusely, and only if
> the amount of heat is in a sufficient quantity. The example with hands
> on either side of the window, IMO would be a case where the amount of
> radiant heat is insufficient. As a counterexample, I would like to
> offer a glass-doored fireplace, with the fire lit, and the doors
> closed. The radiant heat from the fire in the fireplace can still be
> felt.
>
Consider this. Far removed from the shadows building
technology is advancing just as fast as guns and such. They are already
have triple pane glass, how long before an IR reflective glass is
developed? In the southern states this would be a huge boon for corps
who would no longer spend gigawatts of power cooling their office
buildings. The windows don't allow IR (and thus a good chunk of the
heat) from the sun in. The increased heating costs in the winter would
be a minimal price compared to the savings in summer, at least in the
southern areas.
Message no. 6
From: Adam Getchell <acgetchell@*******.EDU>
Subject: Re: IR and Glass [was: Camo and Ruthenium]
Date: Mon, 10 Aug 1998 08:27:34 -0700
>You can see near IR light and near UV light both through glass,
>IIRC (I've used the IR light on night vision goggles as well as a UV
>laser sight through a window before.)

I had use of a thermographic setup while helping develop camouflage. The
most transmissive IR bands through the atmosphere are at 2500 nm and 25000
nm. At those wavelengths, glass is opaque.

The transmissivity curve for the IR spectrum through atmosphere is such
that other wavelengths would have severely limited range (transmissivities
below 20%).

>--Droopy

--Adam

acgetchell@*******.edu
"Invincibility is in oneself, vulnerability in the opponent." --Sun Tzu
Message no. 7
From: Ulrich Haupt <sandman@****.UNI-OLDENBURG.DE>
Subject: Re: IR and Glass [was: Camo and Ruthenium]
Date: Mon, 10 Aug 1998 17:46:41 +0000
bryan.covington@****.COM wrote:
> They are already
> have triple pane glass, how long before an IR reflective glass is
> developed? In the southern states this would be a huge boon for corps
> who would no longer spend gigawatts of power cooling their office
> buildings. The windows don't allow IR (and thus a good chunk of the
> heat) from the sun in. The increased heating costs in the winter would
> be a minimal price compared to the savings in summer, at least in the
> southern areas.

You don't have increasing heat costs in the winter if you use IR reflecting
glas. Since no heat escapes the offices by radiation you save energy and
money in fact!

Sandman
Message no. 8
From: Adam Getchell <acgetchell@*******.EDU>
Subject: Re: IR and Glass [was: Camo and Ruthenium]
Date: Mon, 10 Aug 1998 08:48:14 -0700
> Consider this. Far removed from the shadows building
>technology is advancing just as fast as guns and such. They are already
>have triple pane glass, how long before an IR reflective glass is
>developed? In the southern states this would be a huge boon for corps

You've got that backwards ... reread my post on greenhouse effect. IR is
not a significant portion of the sun's spectrum. Glass is already opaque to
IR.
--Adam

acgetchell@*******.edu
"Invincibility is in oneself, vulnerability in the opponent." --Sun Tzu
Message no. 9
From: bryan.covington@****.COM
Subject: Re: IR and Glass [was: Camo and Ruthenium]
Date: Mon, 10 Aug 1998 11:49:52 -0400
> > They are already
> > have triple pane glass, how long before an IR reflective glass is
> > developed? In the southern states this would be a huge boon for
> corps
> > who would no longer spend gigawatts of power cooling their office
> > buildings. The windows don't allow IR (and thus a good chunk of the
> > heat) from the sun in. The increased heating costs in the winter
> would
> > be a minimal price compared to the savings in summer, at least in
> the
> > southern areas.
>
> You don't have increasing heat costs in the winter if you use IR
> reflecting
> glas. Since no heat escapes the offices by radiation you save energy
> and
> money in fact!
>
Fair enough if it's two way reflective. I was thinking
one way but two way would work much better. I think heating would still
be pricier since you aren't gaining anything from the sun.
Message no. 10
From: Alfredo B Alves <dghost@****.COM>
Subject: Re: IR and Glass [was: Camo and Ruthenium]
Date: Mon, 10 Aug 1998 11:01:24 -0500
On Mon, 10 Aug 1998 09:48:50 -0400 bryan.covington@****.COM writes:
<SNIP>
> Consider this. Far removed from the shadows building
>technology is advancing just as fast as guns and such. They are already
>have triple pane glass, how long before an IR reflective glass is
>developed? In the southern states this would be a huge boon for corps
>who would no longer spend gigawatts of power cooling their office
>buildings. The windows don't allow IR (and thus a good chunk of the
>heat) from the sun in. The increased heating costs in the winter would
>be a minimal price compared to the savings in summer, at least in the
>southern areas.

They have polarized glass (or plastic) that adjusts according to the
amount of light. (In both SR and in RL) So why not something that does
the same for IR? It would keep heat out when it's hot and in when it's
cold outside. That'd be pretty spiffy regardless of where you live :)

D. Ghost
(aka Pixel, Tantrum, RuPixel)
o/` Trideo killed the Video Star ... o/`

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Message no. 11
From: Adam Getchell <acgetchell@*******.EDU>
Subject: Re: IR and Glass [was: Camo and Ruthenium]
Date: Mon, 10 Aug 1998 10:26:59 -0700
>On Mon, 10 Aug 1998 09:48:50 -0400 bryan.covington@****.COM writes:

>They have polarized glass (or plastic) that adjusts according to the
>amount of light. (In both SR and in RL) So why not something that does
>the same for IR? It would keep heat out when it's hot and in when it's
>cold outside. That'd be pretty spiffy regardless of where you live :)

Physics correction ... you (or your house) don't get hot from the IR
radiation from the sun. You get hot from the visible light from the sun,
which is absorbed by molecules. Blackbody radiation says that an object
around 300K will radiate primarily in IR, but that's a heat loss mechanism:
it is not the major source of heat energy exchange. Convection and
Conduction are: radiation is a random process (due to QM)

The sun's spectrum is primarily yellow (Type G4 star); hence the major
portion of energy radiance is in yellow and visible light waves. The
earth's atmosphere is also primarily transparent to visible light, but
tends to screen out other wavelengths. Portions of IR, UV still get
through, but most ionizing radiation is blocked out by the ionosphere.

Screening out IR would not keep you cool. Screening out visible light would.

>D. Ghost
--Adam

acgetchell@*******.edu
"Invincibility is in oneself, vulnerability in the opponent." --Sun Tzu
Message no. 12
From: Paul Gettle <RunnerPaul@*****.COM>
Subject: Re: IR and Glass [was: Camo and Ruthenium]
Date: Mon, 10 Aug 1998 13:32:08 -0400
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At 11:42 AM 8/10/98 -0500, George wrote:
<<snip some science>>
>Heading back to why sunlight warms us through a window, we again rely
on
>the Planck distribution. The sun radiates energy like a perfect
blackbody
>source at 5300K (well, not exactly, but close enough). The peak of
the
>energy distribution for a source at this temperature is, strangely
enough,
>in the middle of what we call visible light. Given the spectal
>transmittance characteristics of common glass, we can see that a bit
more
>than 92% of the solar energy incident on a window passes though it.
>Afterwards, it can be absorbed (by skin, clothing, walls, etc.) or
>reflected back at the window. So, while the solar energy passing
through
>the window is not, strictly speaking, in the IR region -- absorption
of the
>energy by skin or other materials will likely be percieved as a
temperature
>rise.

How about the other example, the glass-doored fireplace? Would that be
similar to above?

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--
-- Paul Gettle (RunnerPaul@*****.com)
PGP Fingerprint, Key ID:0x48F3AACD (RSA 1024, created 98/06/26)
C260 94B3 6722 6A25 63F8 0690 9EA2 3344
Message no. 13
From: Greg Symons <gsymons@******.TEMPLE.EDU>
Subject: Re: IR and Glass [was: Camo and Ruthenium]
Date: Mon, 10 Aug 1998 13:55:53 -0400
{snip a lot of science]
>So, while the solar energy passing
>through
>>the window is not, strictly speaking, in the IR region -- absorption
>of the
>>energy by skin or other materials will likely be percieved as a
>temperature
>>rise.
>
>How about the other example, the glass-doored fireplace? Would that
be
>similar to above?

I would think that since it's in such close proximity to the heat
source that it'd be absorbed and then re-radiated heat. But that's
just a gues:)

Greg



*********************************************************************
* *
* \ (__) Greg Symons <gsymons@******.temple.edu> *
* \\(oo) Seanchai/ and Follower of Bri\de *
* /-----\\\/ *
* / | (##) "Hearken closely and you shall hear the *
* * ||----||" sound of cows and bagpipes upon the heath" *
* ^^ ^^ *
*********************************************************************
Message no. 14
From: George Ayers <ghayers@****.EDU>
Subject: Re: IR and Glass [was: Camo and Ruthenium]
Date: Tue, 11 Aug 1998 15:57:34 -0500
At 12:32 -0500 on 8/10/98, Paul Gettle wrote:
> At 11:42 AM 8/10/98 -0500, George wrote:
> <<snip some science>>

<snipped solar energy distribution example>

>
> How about the other example, the glass-doored fireplace? Would that be
> similar to above?
>

Hmm, paper combusts at about 500 K (not sure what the combustion
temperature wood is, but it shouldn't be too far from this), which would
put the radiation coming from the burning paper in the emission dominant
regime for borosilicate glass. This means that most of the radiation
incident on the glass would be absorbed by and re-emitted from the glass.

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
George H. Ayers | EMAIL: GHAYERS@****.EDU
Mechanical Engineering | PHONE: (409)845-9598
Texas A&M University | WWW: http://acs.tamu.edu/~gha5538/
College Station, TX 77843-3123 | Scholar, Scientist, Coffee Achiever
Message no. 15
From: Spike <u5a77@*****.CS.KEELE.AC.UK>
Subject: Re: IR and Glass [was: Camo and Ruthenium]
Date: Tue, 11 Aug 1998 22:40:17 +0100
|Hmm, paper combusts at about 500 K

Shouldn't that be 451 K... Oh, forget it. I was thinking Farenhiet.
(Hence the name of the book)

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Further Reading

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