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Topic: roasting "parameters", (15 msgs / 332 lines)
1) From: Deward Hastings
<Snip>
'Scuse me for getting gnarley here, but "parameter" is a dangerous word, as
it has different meanings in mathematics, engineering, computer programming
and "common usage".  In other word, it kinda doesn't mean anything any more.
In the example above its use lumps both independent and dependent variables,
and thus obscures the difference between what is controlled and what is
controlled for.  We control batch size . . . that's an "independent
variable", at least until the roast begins, at which point it becomes a
"parameter" for that particular roast, at least in some usages of the word.
We do not control temperature or time.  Those are "dependent variables"
that we control *for* . . . targeting a particular bean mass temperature at
a particular time (relative to the start of the roast).  The significant
independent variable that we control *during* the roast is power, from which
derives the transfer of heat to the bean mass, where it causes the
temperature of the beans to rise (among other things . . . in the initial
stage of the roast some of the heat evaporates water and dries the beans,
later in the roast some smaller amount drives endothermic chemical reactions
in the beans).
The "art" of roasting lies in varying the power input to the roaster during
the roast to accomplish a desired temperature/time response in the bean
mass.
In most roasters the primary mechanism of heat transfer to the beans is air,
which is heated separately to a temperature higher than the beans and then
blown through the bean mass ("air roaster") or the beans are mechanically
agitated and tumbled through the hot air ("drum roaster").  Direct contact
heating, as may be found in wok or skillet roasting, is not common, and even
there a considerable part of the heat transfer is by air, as the actual
contact area between bean and metal surface is small.  Heat transfer (the
rate of transfer) from air to the beans (given adequate exposure or
"mixing") is a function of the temperature difference between the air and
the beans . . . greater difference giving greater transfer.  For the roast
to progress the air must be hotter than the beans.
Direct measure of the temperature of the beans (bean mass) is difficult,
since during roast the beans are surround by hotter air, and it is difficult
to measure bean temperature apart from air temperature (IR thermometers
would do that, but they are difficult to implement).  Air temperature in the
roaster is, however, relatively easy to measure, and that is what most
"automated" roasters (like the Behmor) aim to control for.  If you know the
starting mass (and temperature, generally assumed the same as starting air
temperature) then if you know the air temperature profile over time you can
predict the bean mass temperature over the same time, and changing air
temperature during the roast (relative to bean mass temperature, or
predicted bean mass temperature) lets the machine (or in some cases the
operator) control the rate of temperature change for the beans . . . in
other words control the roast profile.
The key point to understand is that raising the air temperature in the
roaster does not immediately change the bean mass temperature, it only
changes the rate of heat transfer to the bean mass.  Allowance must be made
(and sufficient power available) for heating the roaster itself and for heat
lost to the 'outside world", and "home roasters" commonly operate with
little or no excess thermal capacity.  Insufficient available power to "turn
up the heat" will slow the roast, and then bean mass temperature may deviate
significantly from prediction, causing "automated" features to lose control
of the roast, that is, to fail.  The system is on the whole rather complex,
and subject to change in uncontrolled (unpredicted) environmental variables.
Good monitoring and provision for operator intervention during the roast is
desirable, and operator intervention to determine the endpoint is all but
required, since the automated roaster generally has no way of knowing if the
roast is proceeding according to prediction and under-roast, or at worst
"third crack", may result.
Deward
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2) From: Brian Kamnetz
Thanks, Deward. I always enjoy clear writing about good thinking.
Brian
On Mon, Aug 25, 2008 at 1:01 PM, Deward Hastings  wrote:
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3) From: Justin Marquez
I *think* what he said was:
1) You folks don't know the difference between a "parameter" and a
"variable".
2) To roast the coffee, the air around the beans usually must be hotter than
the beans
3) To roast faster, add more heat.
4) The operator ultimately controls the roast and if he isn't careful a fire
could start!
(He should perhaps consider a career in civil service.)
Safe Journeys and Sweet Music
Justin Marquez (CYPRESS, TX)
On Mon, Aug 25, 2008 at 12:11 PM, Brian Kamnetz  wrote:
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4) From: Deward Hastings
<Snip>
. . .
<Snip>
Great (over)simplifications, completely missing each of the points.
You should consider a career in (Republican) politics . . .
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5) From: Rich
Maybe has a future writing for the Code of Federal regulations.
Justin Marquez wrote:
<Snip>
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6) From: Brian Kamnetz
Deward,
Just a caution... the list is just recovering from a bout of bad
feelings based in political differences. Tom has worked very hard to
try to convince listers that nothing good happens to a coffee roasting
list when politics are injected. People have been very good the past
few months about respecting his wishes in this regard. I personally
would hate to see another bout of bad feelings based on differing
politics. I encourage all listers to confine their discussion to
things other than politics.
Respectfully,
Brian
On Mon, Aug 25, 2008 at 2:12 PM, Deward Hastings  wrote:
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7) From: Stephen Carey
Bravo, Brian.  You got it out before I could.  What was written, 
whether people found it confusing or not, doesn't matter.  What does 
is the spirit of helping others out.  Email bashing is beyond what 
this list needs or it members need to stoop to.  And certainly no 
politics.  Tom has been very patient with the list.
And, for the record, I learned things from most of the email 
responses.  We all have so much to share, for each roast can offer 
its own little story.  Let's hear those and learn from each 
other.  Just my couple of beans worth.
Stephen
At 02:31 PM 8/25/2008, you wrote:
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8) From: Deward Hastings
<Snip>
feelings based in political differences. 
Brian:
But the "career in civil service" doesn't count as "political", eh?  Just a
gratuitous *personal* insult, to be dismissed merely as coming from an
********** *********?
Respectfully,
Deward
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9) From: Brian Kamnetz
Deward,
As I mentioned, we had a bout of bad feelings on the list a few months
ago due to expressed differences in political outlooks. Tom had to
take time from his busy schedule to baby-sit us. It was ugly.
Personally, I greatly enjoyed your post, as I mentioned in a brief
comment. I personally was surprised by, and disappointed in, some of
the responses to your post. I thought the responses, especially to a
relatively new list member, could have been much more genial and
welcoming, which is common here. I'm sorry that you experienced the
exceptions.
Brian
On Mon, Aug 25, 2008 at 7:09 PM, Deward Hastings  wrote:
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10) From: Bill
I agree with Brian.  I should have posted earlier that I thought that your
post was right-on.  I have a contrarian nature, so I oftentimes only post if
I disagree with something.  I thought that the original post was great,
especially the discussion of heat transfer from air to the beans.  That's
definitely the case with my HG/BM roaster.  Another thread is prompting me
to tweak my bread machine so that I can more clearly measure the air temp in
my roaster, so I can observe that heat transfer.
Great post.  thanks
bill
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11) From: raymanowen
"The "art" of roasting lies in varying the power input to the roaster during
the roast to accomplish a desired temperature/time response in the bean
mass."
Agreed- but the "art" of roasting may eventually degenerate to learning
which button to push. The resulting information interchange would be totally
lost on the button pusher that missed the voltage shift.
Cheers, Mabuhay -RayO, aka Opa!
Got Grinder?
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12) From: miKe mcKoffee
<Snip>
<Snip>
Yes, Got 7 grinders not including whirly-chop for spices. Beyond that
doesn't matter whether which button(s) to push (and when), what automated
profile to run, what lever to pull, what knob to turn, how far to hold a
heat gun, how high a flame and how fast to stir the wok etc. The "Art" is
only lost when the creator of the profiles(s) leaves the equation.
Kona Konnaisseur miKe mcKoffeehttp://www.mckoffee.com/Ultimately the quest for Koffee Nirvana is a solitary path. To know I must">http://www.mcKonaKoffee.comURL 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.
Pacific Northwest Gathering VIIhttp://themeyers.org/HomeRoast/Homeroast mailing list">http://home.comcast.net/~mckona/PNWGVII.htmSweet Maria's List - Searchable Archiveshttp://themeyers.org/HomeRoast/Homeroast mailing list
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13) From: Stephen Carey
Wonderfully said, Mike.  For, in the end, it is the desire and dream 
to take the bean to where it was meant to go, and that takes the 
person to do so.
Stephen
At 11:18 PM 8/25/2008, you wrote:
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14) From: Justin Marquez
Deward,
Of course it was a great oversimiplification. That was the point. Perhaps I
should skip trying for a career in humor.
Safe Journeys and Sweet Music
Justin Marquez (CYPRESS, TX)
On Mon, Aug 25, 2008 at 1:12 PM, Deward Hastings wrote:
<Snip>
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15) From: Justin Marquez
Deward,
If my attempt at humor offended you, I hereby publicly apologize.  I was
just joking about the long post. The reference to "civil service" was just
because every so often, you see examples of loooong descriptions from some
civil service manual, government reports, etc. It just struck me as funny.
Apparently, I am the only one who felt that way, so again, my apology is in
order and I offer it.
Safe Journeys and Sweet Music
Justin Marquez (CYPRESS, TX)
On Mon, Aug 25, 2008 at 6:09 PM, Deward Hastings wrote:
<Snip>
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