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Topic: IR measurement and WOK roasting (5 msgs / 141 lines)
1) From: james McDougal
This was my second attempt at roasting (so take it with a grain of salt!). I
was waiting for the rigid ss probe that several of us ordered (thanks Martin
Dobbins) to try roasting on the stainless steel stovetop roaster again, but
was out of coffee and wanted to *roast something! *
I have a dark colored WOK and an IR surface temperature measurement device
with the little laser dot, so I thought I'd try roasting 1/2 lb of tanzania
nyamtimbo peaberry to city+ (435 deg) in the WOK. According to the IR probe,
I heated the WOK to 400 (took longer than I thought it would) on high heat.
Put the peaberry in and used a slightly concave stainless steel stirrer with
holes to move the beans from the edge in all directions and then spread them
out 1-2 layers thick in the WOK, pause 10 seconds and start over. I tried to
measure the temperature of the topmost beans when they were spread out in
the WOK, at one minute intervals. Started to get a little smoke at 6 min
(309 deg) and a small amount of chaff. First crack seemed to go from 9-11
minutes (340-350 deg) the beans were nearly uniformly light brown and
everything seemed fine.  The temperature the IR probe basically stopped
increasing rapidly and  ranged from 360 to 380 over the next 9 minutes.
Smoke noted at 15 and 18 minutes. It became obvious that something was wrong
and I quit at 20 minutes (380 deg) and went outside to pour the beans
between 2 collanders. The bean munch had a distinct burnt taste on some
beans. Trying to decide whether to throw them out or mix them.
What happened? I've read comparisons with IR and TC reading that were close.
Could it be that in an open WOK (under a really good range hood) the
outermost surface of the beans cools off quickly, and I wasn't getting a
good measurement? Were the other IR measurements in a closed system? It
wouldn't be possible to measure the temperature of the beans through glass
of roasters would it? I liked the idea of being able to watch and smell the
beans and chaff wasn't a problem. Can anyone who uses(ed) a WOK or dog bowl
relate to what happened?
Jim
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2) From: Bill
Jim, I reported about the IR and the TC.  A thought, that was in a HG/BM
setup, measuring from above, which is also where the HG is pouring heat in.
 A bit different than a stovetop.  Which tells us that an IR is useful, but
not the be-all and end-all.  Fairly typical of all instrumentation.
If you were having first happen at 340, that's a lot lower than in a closed
system (around 400F there).  Not a big deal, just tells us that there is
indeed a lot more cooling happening in the wok for the top layer.
If you were at 380, that should be 2nd crack.  That's 40 degrees above your
first crack temp.  That's what's stumping me.  I think there are a few
possibilities:
1.  You ran first and second together and didn't know it, and then continued
to burn the beans.  I doubt this, because you say after first they were
light brown and also because this would have produced a lot of smoke!
2.  You got through first and just didn't have the heat to get into 2nd.  Or
not enough time...
3.  There was no audible 2nd crack.  Which I doubt.
I think it might be the second, but I'd like to hear from other listers to
know what they think.  You should definitely try some of those beans to see
just how good/bad they really are!
bill
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3) From: james McDougal
Bill, Thanks for your input! I think your number 1 option is correct.
I tasted the beans this morning and they are drinkable (I like dark roast),
but I'd say a little thin (not sure of all the correct terms). Sure would be
nice to be able to take a "cupping" class.
Cheers, Jim
On Mon, Aug 25, 2008 at 4:36 PM, Bill  wrote:
<Snip>
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4) From: Rick Copple
james McDougal wrote:
<Snip>
I've roasted in a wok for nearly 3 years as my standard method. However, 
I never attempted to measure the temp. From what you're saying, I 
suspect the beans were scorched to some degree, perhaps by sitting too 
long on one side and on too high a heat setting.
For a half pound of coffee, I would raise my electric range knob up to 6 
(on a 0 - 9 scale) to preheat for a minute or two, sometimes I wouldn't 
preheat at all if I wanted the beans to have a slower ramp, then toss 
the beans in and knock it down to 4.5. I would uses a wooden spoon to 
"stir fry" the beans in the wok, so I'm moving them around continually 
like a stirrer in some of the other roasters. After about 9-12 minutes, 
I would get some first crack. As that is winding down, I would lower the 
heat to 3.5 on the dial, and that would take it to whatever roast level 
I wanted, anywhere from 15 to 20 minutes depending on how dark I'm 
shooting for.
I've only scorched the beans when I attempted to roast half a pound and 
used too high of heat, like 5 or higher on the dial. For one pound, 
which is what I usually roasted, my dial settings were 6 to preheat, 5 
to first crack, and 4 to desired roast level.
Maybe that will give you some idea where your's might have veered off 
track even though my range dial may differ from yours to a degree.
-- 
Rick Copplehttp://www.rlcopple.com/Homeroast mailing list
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5) From: james McDougal
Thanks, Rick!
I must have had the heat way too high as you suggest. I had it at 9 because
it didn't seem to hold the heat well with the curved surface. Now I know!
I'll try again - I do like the idea of being able to watch what is going on
with the beans. I've used the stovetop roaster a couple of more times and
don't have an indoor chaff problem. Do you have a chaff problem with the DP
beans or others that put out a lot of chaff?
Jim
On Mon, Sep 1, 2008 at 1:30 AM, Rick Copple  wrote:
<Snip>
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