HomeRoast Digest

Topic: IR2 Profile (17 msgs / 551 lines)
1) From: Larry Williams
I have roasted quite a few batches using the Preset 2 - usually stopping 
the roast with about 2:30 left in on the timer.  Since I can't hear the 
crack (ringing ears I guess) I stop the roast at the first sign of oil 
on the beans.  The method has worked great for me and every cup has been 
great.  It has has truly been unbelievable what the difference has been 
with roasting as opposed to buying even good quality roasted beans.  No 
comparison!  Every bean is slightly different, but we haven't tasted one 
we didn't like.
I am interested in developing my own generic profile.  I know this 
sounds simplistic, but I really don't want to mess with a long list of 
specific profiles for each region.  From what I have gathered on the 
list it is desirable to extend the time to the first crack as long as 
possible and ramp up the temp gradually. 
Tom and IR2 starts with 350F for about 3 min and finishes around 450F.  
My display usually indicates 405F at my finish (when I hit cool).  I 
understand that the display is about 50F less than the profile setting.  
What is a good profile for the steps between 350F and 450F?  Can I use 
the entire 15 min and not turn the beans to charcoal?
Larry Williams
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2) From: Mejia, Carlos
I don't mean to highjack your message, but I'm in the same situation and
have the same goal as you.  I just got my IR2 in early December and have
don't about 20 roasts, mostly using Tom's suggested profiles that came
on the Tip Sheet sent with the roaster.  I'm wondering if there isn't a
'near perfect' ramp program that can be used for all beans, just
stopping the roast at different times depending on the color of the
beans.  Also, wondering if any IR2 roasters out there can explain how to
add a thermocouple to the machine.  I would rather measure the temp of
the beans instead of relying on the air temp.  Maybe there's a good
website showing how to make this modification?
Carlos Mejia

3) From: Jeff Bensen
Carlos / Larry -
At 01:29 PM 2/4/2007, Mejia, Carlos  wrote:
I have an iRoast-1, and documented the end-point of my journey to add 
a thermocouple for measuring the temperature of the bean mass:http://mpinet.net/~jbensen/I'm not sure if the iRoast-2 chaff collector is exactly the same, but 
perhaps this will give you some ideas.
At 8:21 AM 2/4/2007 Larry Williams wrote:
I have a 'standard profile' that I use as a starting point. Note that 
your setup and the temperature response of your particular machine 
will probably be different than mine. I also roast indoors, with a 
near-constant ambient temperature, which helps my consistency. The 
goal of my standard profile is to get to the verge of first crack in 
6 to 7 minutes. I'm not sure how much this profile description will 
help you. Nevertheless, here goes.
For my setup, I use:
Stage 1: 325 F / 3 minutes / 120 VAC
Stage 2: 385 F / 3 minutes / 120 VAC
Stage 3: 390 to 400 F / 9 minutes / (voltage varies*)
These programmed temperatures are lower than what I have seen others 
post, but I believe my machine may be one of the hotter ones.
For Stage 3, I'll generally use 390 for larger beans (i.e.: Kona), 
395 for medium (most beans), and 400 for small ones (i.e.: Yemen). 
Because the fan speed shifts to slow with my unit starting at the 390 
F setting, I'll sometimes bump the Variac up to 123 VAC to keep the 
beans lofting until they lose enough moisture and expand enough to 
loft well (usually around 400 to 410 F bean mass temperature), then 
bring the voltage back down to 120 VAC for the rest of the roast. I 
then hit cool when the appropriate temperature is reached, usually 
with about 4 minutes left in the programmed profile.
- Jeff Bensen
   Palm Bay, FL
At 01:29 PM 2/4/2007, Mejia, Carlos  wrote:

4) From: Brian Kamnetz
Great stuff, Jeff.
On 2/4/07, Jeff Bensen  wrote:

5) From: Michael Dhabolt
Jeff Bensen wrote:
Nice modification and great documentation.
Mike (just plain)

6) From: Larry Williams
Jeff Bensen wrote:
Thanks Guys
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7) From: Larry Williams
Why does every one always use 3 min for the first stage?  Why not longer?
Jeff Bensen wrote:
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8) From: raymanowen
Hi, Carlos,
I don't think any temperature measuring instrumentation has the capability
of giving more than a Fraudulent Number that is Not the actual bean
temperature. No more so than a meteorologist could say that any number is
The Temperature of North America.Temperature is not uniform from north to
south and east to west.
When you start applying heat to a coffee bean to roast it, you raise its
temperature starting from the outer surface. The heat always heads for the
colder zones and heats them up. The center of the bean is always last to get
hot, so least roasted.
When the entire roast is completed in less than 20 minutes, there are some
mighty wild temperature gradients as the temperature applied to the bean is
quickly shifted.
Imagine they grow coffee in Brobdingnag. Gulliver is harvesting the green
bowling balls. Drill a finger hole to the center for a thermocouple in one
of the bowling balls. Throw it in with the hundreds of other bowling balls
in your Brobdingnagian roasting oven as the control sensor or roast
Obviously, the whole green coffee bowling bean won't be the same temperature
from surface to center as heat flows in or out of the bean. The
Brobdingnagian PID temperature controller is well set up and learns the
sensor's hysteresis within the first temperature cycle.
Physics or thermodynamics on Brobdingnag is the same as here or Liliput, and
the bowling bean has a different roast from its outer layers to the center.
One solution might be to heat with infra red and microwave power, the two
being identical forms of energy at drastically different frequencies.
Microwaves, at a much lower frequency and longer wavelength than near or far
infrared radiation would tend to permeate the beans deeper before becoming
heat energy- "heat from within."
A Cornell studyof
the subject made me wonder about the IR / microwave application to
Cheers -RayO, aka Opa!
The roast is so uniform, the beans all crack at once - 1st BOOM - - 2nd BOOM

9) From: Jeff Bensen
At 12:20 AM 2/5/2007, raymanowen wrote:
Ray -
I agree with your statement completely -- I do not for a moment 
believe I am measuring the 'actual bean temperature'. That is not to 
say, however, that such a measurement is worthless.
By having my probe in the same place within the roasting chamber 
every time, I minimize the inconsistency in temperature readings due 
to heat variations throughout the chamber.
Then over time I have come to learn that, in my particular setup, a 
given final temperature target roughly relates to a given roast 
level. I may slightly alter the final temperature target for the type 
of beans I am roasting due to their size, density, moisture content, etc.
Using this metric, along with sight, sound and smell, has helped me 
to achieve a good level of consistency and repeatability in my 
roasts. It has also enabled me to approximate the more elusive City+ 
and Full City roast levels in the iRoast-1.
- Jeff Bensen
   Palm Bay, FL

10) From: Larry English
All valid, RayO, but nevertheless, a probe in the bean mass gives a much
more useful gauge as to the roast level of the beans that does any built-in
temp reading in any home roaster I know of.  It is undoubtedly fraudulent as
an absolute measure of heat but also undoubtedly useful as a measure of
roast progress, and I don't think that's a paradox.  In forced-air roasters,
you're getting the temp of air either entering or leaving the chamber; that
could be constant while the bean mass temp is increasing up to and past 1st
crack, on to 2nd crack, and heading towards carbon.  I'm not even sure what
the iRoast2 temps mean but by roasting with a probe, I get repeatable
results.  On the Gene Cafe, 1st crack occurs somewhere around 450F on the
readout but that is surely not any reasonable measure of the bean temps.
On 2/4/07, raymanowen  wrote:

11) From: Larry English
Looks like Jeff and I were thinking along the same thought line and
timeline. I wish I could put a probe in my Gene Cafe, though I am able to
hear the cracks there (I couldn't in the iRoast2).
On 2/4/07, Larry English  wrote:
"You can't know the unknowable, but you can do the doable." - Jon Carroll

12) From: Jeff Bensen
Larry -
I can only speak for myself on this. I have tried longer first (and 
second) stage times. On some beans, the temperature will reach a 
maximum before the end of a longer stage, then it will hold steady 
until the next stage starts. On roasts where this has happened, the 
coffee tasted flatter (not as flavorful) to me compared to those 
where I had the temperature constantly increasing throughout.
I can't claim to be an authority on this, I only go by what tastes 
good to me. I believe that the key to this journey is to experiment 
and see what works for you.
- Jeff Bensen
   Palm Bay, FL
At 08:07 PM 2/4/2007, Larry Williams wrote:

13) From: raymanowen
You're all right, and we're on the same page.
The final arbiter is Your Palate. Does the Fruit of Your Roaster taste
Fabulous to you, and can you repeat it? You're hitting Home Runs!
Cheers -RayO, aka Opa!
*Disclaimer:* Statements contained herein have not been evaluated by the
SCAA. This free advice is worth every penny and is not intended to diagnose=
treat, cure or ameliorate any roasting SNAFU. Always consult your
professional cupper to see if it's right for you…
On 2/4/07, Larry English  wrote:
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ct-02.htm>of the subject made me wonder about the IR / microwave applicatio=
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"When the theme hits the bass, I dance the Jig!" - -Virgil Fox at the Might=
Wichita (ex- NYC Paramount) WurliTzer- 1976

14) From: Mejia, Carlos
Jeff...  Thank you for the link to your documentation.  This is
awesome!..exactly what I was looking for.  I understand that such a
setup will not measure the actual bean temp but I think it should be
less affected by the strong airflow and should provide a better means of
monitoring the stage of roast. Is there anything special I should know
about the thermocouple before I go out to buy one?   Any recommendation
on brand or source for this?
Thanks again!   ~carlos

15) From: David Schooley
If you want to install a thermocouple without drilling a hole in your  
machine, you can go through the bottom. You remove the four screws  
holding the bottom of the roasting chamber in place. You then run the  
wire down the outside of the glass and back up on the inside. There  
is an o-ring that separates the metal plate from the glass and  
plastic. You will want to keep the wire outside the o-ring so that  
the wire does not come into contact with the metal plate. Everything  
locks into place once you reinstall the bottom. You will not be able  
to adjust the wire after the bottom is back on, so you need plan  
ahead to get the length right. From inside the roast chamber, my TC  
wire goes up a quarter inch or so and then toward the center of the  
chamber for an inch or so. This puts it right into the bean mass. I  
took some pictures today, but I need to do them again when I can get  
better light.
On Feb 4, 2007, at 12:29 PM, Mejia, Carlos wrote:

16) From: Mejia, Carlos
Great.  I would rather not drill holes through my iR2 if I can avoid it.
A picture would be helpful.   Thx ~carlos

17) From: Jeff Bensen
At 01:33 AM 2/5/2007, Mejia, Carlos wrote:
The following detailed (and potentially boring) discussion relates 
specifically to my installation in the iRoast-1:
I'm using a K-Type thermocouple probe, encased in a 6" long by 1/8" 
diameter stainless steel sheath. I chose stainless for several reasons:
- The stainless steel sheath is inert in this application.
- A fiberglass sheath can slowly erode over time into the bean mass 
while roasting, leading to possible ingestion of fiberglass particles.
- A Teflon sheath presents potential health problems (begins to 
outgas toxic particulates when heated in excess of 446 F, well within 
potential roaster temperatures).
- A Kynar sheath can begin to melt at as little as 329 F. Although I 
seem to recall seeing some variants that claim to be stable to around 
500 F, that is still borderline in a roaster in my opinion.
Furthermore, the encased probe provides for a rigid assembly which 
does not significantly change in shape or position from one roast to the next.
I went with 1/8" because I believe this to be a good tradeoff between 
rigidity and the thermal inertia of the probe. Furthermore I chose a 
grounded junction probe (where the thermocouple junction is in 
contact with the inside surface of the tip of the sheath) in order to 
more rapidly track the changes in temperature within the roast 
chamber, since electrical isolation is not required in this 
particular application. This results in roughly a 10 second response 
time. If you went with a 1/16" diameter sheath the response time 
would drop to around 3 seconds, but the probe would be more prone to 
accidental bending.
The downside is that you *do* have to drill a hole in the iRoast 
chaff collector.
There are numerous sources for probes like this. The one I'm using is 
an Omega model KTSS-HH. It will work with any K-Type thermocouple 
meter that accepts miniature connectors ("SMP" type) which includes, 
I believe, the model offered by our hosts.
- Jeff Bensen
   Palm Bay, FL

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