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Bob (this one) Bob (this one) is offline
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Default Baking cakes in foil pans

wrote:
> Bob (this one) wrote:
> s foil pans reflect heat.
>
>>I did as you suggested. *All* the hits were from non-scientific sites,
>>with the words sounding like they were written by the same person. You
>>need to evaluate the sources of your information better than you did.
>>None were authoritative, and merely parroted each other.
>>
>>Now look at the technical sites...
>>
>>"If metal is a conductor of heat, why is it that aluminum foil will
>>insulate food and reflect heat?
>> "Aluminum may be a good conductor of heat, but its a terrible
>>emitter or absorber of thermal radiation. When you wrap food in aluminum
>>foil, you dramatically reduce that food's ability to lose heat via
>>radiation if it's hotter than its surroundings or its ability to gain
>>heat via radiation if it's colder than its surroundings. Aluminum foil
>>doesn't have much effect on heat transferred to or from the food via
>>conduction or convection because aluminum itself is a good conductor of
>>heat." <http://rabi.phys.virginia.edu/HTW/clothing_and_insulation.html>
>>
>>"...terrible emitter or absorber of thermal radiation" means that it
>>doesn't reflect it, it simply doesn't absorb it. It doesn't make it go
>>back where it came from, nor does it capture it.
>>
>>See that "good conductor of heat" thing? Not "reflector" of heat.
>>
>>Here's another one:
>>"2.132 Reflect radiant heat waves
>>Heat tissue paper with a magnifying glass, as in 2.131. Note the
>>distance from the reading glass to the tissue paper. Put a tilted mirror
>>half way between the lens and the paper. Feel with your hand above the
>>mirror until you find the point where the heat waves are focussed. Hold
>>a piece of paper tissue at this point. The paper ignites."
>>
>>That wouldn't happen in the dark. Light is radiant heat. It reflects
>>light. It doesn't reflect heat as heat, it just doesn't absorb radiant
>>energy well, nor does it transmit it. You say it reflects heat, so I'm
>>sure you'd closely wrap your hand in a single layer of foil and hold a
>>candle under it such that the flame was 1/2 inch below it. It'll reflect
>>the radiant heat (we call that light) but the conducted heat and
>>convected heat will fricassee your hand. That's why aluminum cookware
>>works well. It conducts heat very well; it doesn't reflect it back
>>towards the flame or the coil.
>>
>>"23.00 Heat & temperature, internal energy & heat, heat and the first
>>law of thermodynamics
>>Heat is a form of energy measured in Joule. The first law of
>>thermodynamics states when other forms of energy are converted to heat,
>>or when heat is converted to other forms of energy, there is no loss of
>>total energy. The second law of thermodynamics states heat always flows
>>from hot bodies to cold bodies. "
>><http://www.uq.edu.au/_School_Science_Lessons/UNPh23.html>
>>
>>Note that aluminum is right behind gold and copper in its capacity to
>>conduct heat (the last column of the chart). Silver isn't mentioned, but
>>it's at the top of the list.
>><http://www.ee.byu.edu/cleanroom/thermal_properties.phtml>
>>
>>"Clearly in selecting a conductor these are very significant differences
>>- so the best materials are those which lie low towards the bottom of
>>the metals bubble, such as copper and aluminium. Gold is excellent, but
>>it is so expensive it is way off the scale of the chart. Even so, it is
>>used for electrical contacts in microcircuits.
>>
>>"Finally, thermal conductivity and electrical conductivity are closely
>>related - as the underlying physics is similar. The electrical
>>resistivity chart also gives an indication of thermal properties - with
>>thermal insulators towards the top (polymers and foams, and ceramics)
>>and the good thermal conductors - metals - at the bottom."
>><http://www-materials.eng.cam.ac.uk/mpsite/physics/introduction/default.html>
>>
>>This means that heat and electricity are treated similarly by metals.
>>Aluminum is a good conductor of electricity, so it's also a good
>>conductor of heat. As nothing reflects electricity, nothing reflects
>>heat, either.
>>
>>You might want to consider why there are charts for conduction of heat,
>>but none for reflection of heat.
>>
>>This whole issue reminds me of that silly device with a hemispherical
>>mirror (like a bowl) into which you were supposed to put ice to reflect
>>the cold upwards and chill things in a small basket at the mouth of the
>>bowl. It was a physical impossibility.
>>
>>Now you go find out what "heat" is and is not. And learn the difference
>>between radiant heat and conducted or convected heat is. And don't go to
>>cooking hobbyist sites for lessons in physics.
>>
>>Pastorio

>
>
> You can quote as much so called


Hey, moron. This kind of sneering dismissal of researched and documented
information marks you for an ignorant fool. When there's data from
several reliable sources and you say, "Oh, no, I know better," you end
up looking like a blowhole driven by ego and the obviously mistaken
belief that it's correct just because you believe it.

> scientific proof


Yes. Scientific proof. As opposed to your confused ramblings that show
you have no idea about heat, its movement and reflectivity.

> as much as you want
> but I know from experience that shiny aluminum baking pans reflect
> heat.


So you say. And you *know* it's reflecting heat rather than simply not
transmitting it. What a wonderful thermal effects laboratory you must have.

<LOL> You *know* what's happening, and then you offer the stuff below as
"proof." Hilarious.

> Besides, there's a big difference between the way a pan heats up
> on a stove and the way a pan heats up in an oven. A pan on a stove
> heats up entirely by conduction.


So the red glow from the electric coil isn't radiant heat. And the very
visible gas flame isn't radiant heat. Got it. I bet your physics teacher
is proud of you.

I bet that's why you're perfectly happy to hold your hand right next to
the pan while it cooks. No radiant heat means none released to the air,
right?

> A pan in an oven heats up by means of
> radiation and indirect conduction, that is the oven's heat source heats
> the air inside the oven and the heat from the air is conducted into the
> pan.


There's no such thing as "indirect conduction." Heat is either conducted
or it isn't. There's a grand total of three ways for heat to move -
radiation, conduction, convection. There's no "indirect" way for heat to
move.

> Since light colored materials reflect radiant energy,


Um, *visible* radiant energy and infra-red. The energy radiating from
hot oven walls isn't visible; too far down on the electromagnetic
spectrum (You do know what that is, right?). That light-colored business
refers to "albedo." And you need to learn the difference between
"shiny" and "light-colored."

> part of the
> radiant heat inside the oven is reflected away from the pan.


You didn't read anything from those science sites at all, did you...?

Like it says above: "You might want to consider why there are charts for
conduction of heat, but none for reflection of heat."

We're done with this. You haven't the remotest idea what you're talking
about. The very simple fact is that you're wrong. The next fact is that
you aren't interested in learning. You're over your head with this subject.

For future reference, one person's anecdotal experience is *never* proof
of an assertion. Not yours, not mine.

Pastorio