HomeRoast Digest


Topic: 2 iRoast temperature questions (4 msgs / 145 lines)
1) From: Stephen Jones
In considering the following questions, please factor in that I have a
variac and should be able to keep voltage pretty constant at 120.
1.  Can the presets be used to determine how far off the temperatures
displayed will be.  Tom says:
"Preset Roast Curves - Specific on the Preset roast curves that come
programmed into the iRoast
Preset #1 : total roast time 11:00 min
Stage 1: 485 F for 6:30 min.
Stage 2: 440 F for 3:00 min.
Stage 3: 485 F for 1:30 min."
Me again - if I do a roast using the Heartware recommended bean volume and
use preset #1, can I then see what temperatures are displayed in stages 1-3
to determine what temperatures I'm going to have to program in to get the
temperatures desired.  In other words, if I see a temperature of 440F during
stage 1, can I assume that the difference between actual and displayed
temperatures is roughly 45F, and tack 45F onto the temperatures that I want
when I do the programming?  
If not, how do I determine the difference in temperature that I'll have to
use?
2.  Using Tom's roast curves
Tom says:
"Here's the roast curve that I use for almost all samples to get a City or
City plus roast (which is considered a cupping roast I know and is probably
lighter than most folks like): 
Total roast time: 9:30 min
Stage 1: 350 F for 2:00 min 
Stage 2: 400 F for 3:00 min 
Stage 3: 460 F for 4:30 min "
Me again - assuming that I was able to determine from #1 above that I have a
45F difference, I assume that I would then set my temperatures to 405F,
445F, and 515F, respectively, to follow his roast curve.  Right?
My iRoast is set for delivery next Tuesday and I want to try to be as ready
as I can to start using it.
Thank you.
Stephen Jones

2) From: Christian Wiedmann
Responses inline, below.
On Thu, 29 Jul 2004, Stephen Jones wrote:
<Snip>
Most people talk about the preset temperatures, not the ones reported, so
there is no difference to calculate for the programming.
However, since your individual roaster may be different than Tom's, you might
have to adjust empirically based on your roasting results.
<Snip>
Actually, no. Start with exactly what Tom used.  The maximum temperature
you can preset is 485 anyway.  Tom is telling you the preset temperatures
he used, not the reported temperatures.
The way you would adjust for individual variation is to tweak the curve
yourself based on results.  I would suggest lengthening the last stage to
the maximum time and then stopping the roast manually until you get an
idea of how fast your roaster is going to go.
	-Christian
<Snip>

3) From: Bob Yellin
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and
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1-3
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the
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during
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want
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to
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You'll get quite close by recording the differences. The kicker is
that the differences change - they're not always the same for two
different roasts with different profiles. For example if you're
recording a difference of 45 deg F at, say, 440 F, you may see a
different difference when you reach 440 F by a different profile. This
will be especially true if you try to use the differences for the
presets because the preset profile uses very radical roast
temperatures (compared to Tom's, for example). On most iRoasts,
including mine, it nearly vaporizes the beans. I wouldn't use the
presets for anything on mine - not to roast and not to calibrate.
<Snip>
or
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probably
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have a
<Snip>
No - you cannot assume that your iRoast will have the same temperature
calibration as Tom's. Some of these iRoasts may be similar and some
may be different. However, you could start with Tom's profile and
record the differences on your machine. That would give you a
realistic starting point to zero in on your desired profile. It may
take a few "sacrificial" roasts. But that's part of the fun, isn't it?
Bob Yellin

4) From: Craig Wichner
<Snip>
calibration as Tom's. Some of these iRoasts may be similar and some may be
different. 
Bob has it right. However, as one datapoint, my roasts were completing much
sooner than Tom's guidelines...until I did the modification at the bottom of
his tip sheet (rotating the plate holding the chaff collector). This did
three things for me:  1) tightened the chaff collector, which had previously
rattled around, 2) the roaster temperature cooled down because less chaff
clogged up the screen, and 3) my roast times now line up almost exactly with
Tom's guidelines (with of course variability by bean type).  When you get
your I-Roast, if your chaff lid doesn't "click" and fit snugly when
"locked", this modification will help, otherwise don't bother.
Quantitatively, on a Kenyan Kora Peaberry, this change added 40 seconds to
my roast time to the first few cracks of second crack (8:25 to 9:05).  On
beans with more chaff, for example dry-processed coffees such as some
Ethiopians and Yemenis, the difference is even longer. 
FYI, if you haven't seen it already, you can track your roasts using the
Coffee Roasting Database found athttp://improbablystructuredlayers.net/CoffeeRoastingDB/CRDBHome.htm(free
and very cool). 
Enjoy!
Craig Wichner


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