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Topic: Exothermic and envirnoment vs bean mass temps (6 msgs / 199 lines)
1) From: John Despres
As the beans warm, collecting heat, they are endothermic. As second =
crack occurs, the beans become exothermic, giving off heat, heating =
themselves, and enabling the roast to become out of control without =
proper adult supervision.
At least that's my understanding of what I've read.
John
wncopeland wrote:
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ond crack.  I bet the beans were  becoming charcoal by then, and therefore =
exothermic.  I believe that there will be no exothermic activity at any roa=
st time that you would normally use.    Bill C.
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/gallery/main.php?g2_itemId=7820
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-- =
John A C Despres
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616.437.9182
Scene It All Productions 
JDs Coffee Provoked Ramblings =
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2) From: miKe mcKoffee
Wrong. Believe want you want. Doesn't change facts or countless years
experience by countless coffee professionals out there.
While roasting have environment temp ~20f lower than bean mass temp going
into 2nd crack and bean mass temp continues to rise. How can bean mass temp
be rising with environment temp lower than bean mass temp if not exothermic?
Answer: Can't.
(I'm not talking about that graph test roast that had gas kept at 100% going
well into 2nd, talking about what I observe on a regular basis.)
Dump beans at 30 seconds into 2nd crack for example and apply no active
cooling other than room temperature air, do the beans keep cracking?
Answer: Yes. 
BTW, why the heck address your reply TWICE to the List and cc to me. I don't
need THREE copies of your reply. Doesn't add impact or value to the post,
it's just annoying.
Pacific Northwest Gathering VIhttp://home.comcast.net/~mckona/PNWGVI.htmKona Kurmudgeon miKe mcKoffee
www.mcKonaKoffee.com
URL to Rosto mods, FrankenFormer, some recipes etc:http://www.mckoffee.com/Ultimately the quest for Koffee Nirvana is a solitary path. To know I must
first not know. And in knowing know I know not. Each Personal enlightenment
found exploring the many divergent foot steps of Those who have gone before.
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3) From: Floyd Lozano
Correct me if I am wrong but to be exothermic, the system has to start
putting out more energy than is being put in, which is to say there is
a chemical reaction that is releasing energy (presumably as bonds are
broken at the molecular level)
<Snip>http://en.wikipedia.org/wiki/Exothermic_reactionUnless one can accurately measure the energy in the system, you can't
know if it's actually exothermic.  You can say for a FACT that the
temperature increase spikes at a point in the roast cycle, for
whatever reason (the beans stop absorbing heat at their prior rate,
presumably due to the stuff that is absorbing the heat in the beans
blowing out as steam and changing the contents of the mass) but
without precise measurements of the energy in the system, I don't
believe one can conclude that there is an exothermic reaction taking
place.
-F
On Tue, Apr 22, 2008 at 8:59 AM, miKe mcKoffee  wrote:
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4) From: Eddie Dove
"When the beans are first dropped into the roaster, a significant drop
in temperature is observed as the beans rapidly absorb ambient energy.
This first phase of roasting is completely endothermic with the
majority of the heat used to drive off as much free water as possible.
As the temperature stabilizes around 100C, water within the bean
begin to form steam and a significant increase in pressure in created.
[...] Once the drying phase has completed, bean temperatures rapidly
increase and the reaction changes from being endothermic to
exothermic."  - Joseph A. Rivera
Eddie
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6) From: Brian Kamnetz
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