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Topic: More Gene Cafe experiments - speeding up roasts/first crack (7 msgs / 183 lines)
1) From: Ken Mary
I never preheat in my homebuilt drum, it is light enough that a preheat does
not gain much time. I nearly always start with full heat, then reduce in one
or more steps depending on the bean. My final turndown is just before first
crack. This timing seems critical in getting enough brightness in the cup.
The trick is getting close enough to first that you get a "loud enough"
crack but still allow the crack to end in a reasonable time, say 1 to 1.5
minutes. My city to city+ roasts are usually 12 to 14 minutes, the time to
first is 10 to 12 minutes.
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roasts.
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2) From: Frank Parth
Scott,
Now you've given me a new profile to try. I'll have to check it out once I start running low of the batch I roastedtwo 
days ago and I'll let you know how it comes out.
Thanks.
Frank Parth
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3) From: John Despres
Scott,
Thanks for the input. I'm wondering what bean(s) you used in your 
experiments. The harder, more dense beans that are typically grown over 
5000 feet need a higher initial heat and less at the final stage and the 
softer beans, typically grown below 3500 feet should be roasted at a 
lower to moderate heat throughout the roast.
I'm guessing your experiment today was a harder bean, maybe a Kenya, 
Guatamala or Sumatra. For control are you using the same bean every time?
Also, after preheating to 360 and the emergency stop, how much does your 
temp drop by the time you've reset the GC for the full roast? I find if 
I want to start with the drum temp at 300, I need to preheat all the way 
to 482 and once I've loaded and set the beginning of my roast, I manage 
to be at about 300 degrees in the drum.
This is fun.
Enjoying a cup of Yemen Mocha Sana'ani (French press) roasted yesterday 
afternoon... I think I'm a bit early and will share my thoughts after 
another 24 hours of resting.
John
Scott Bukofsky wrote:
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John A C Despres
Hug your kids
616.437.9182http://www.sceneitallproductions.com

4) From: John Despres
Me too, Ed. I thought extending the roast gets us into the deeper, 
darker flavors... Or am I mistaken? If I am, why?
John
Ed Needham wrote:
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John A C Despres
Hug your kids
616.437.9182http://www.sceneitallproductions.com

5) From: Ken Mary
Ed,
I put the turndown point closer to the start of first when I want more
brightness (more and louder cracks). Typically, first crack starts at 205C
bean temperature. So the brighter profile has the final turndown temperature
at 195 to 200C while the normal profile's is 185 to 195C. One of my Brazil
profiles is turned down at 100C, but the final heat input is higher than
other coffees. Brightness can be lost with too much time between 190C and
the start of first, and by taking too much time to get through first crack.
A turndown point of 205C shifts the apparent start and finish of first crack
to higher temperatures and risks running into second without a pause.
Eddie Dove said, "The amount of heat applied during the roasting process is
decreased, but not to the extent that the bean temperature drops; the
temperature of the beans continues to climb.  This is a method I learned
well on the Gene Cafe."
This is correct, and with the advantage of monitoring bean temperature, I
can observe the ramp in the first crack endotherm. While that ramp sometimes
approaches zero, it never goes negative. This endotherm occurs mainly in wet
process beans. My latest Brazil (dry process) roast had a longer than normal
development, and presumably lost enough water so that first crack seemed to
go exothermic. Actually, I believe that this was an extension of the Sivetz
Bump, since the ramp began to increase prior to first. On completion of
first, the ramp resumed its normal pre-first rate. This may be something you
large batch roasters need to watch out for. Roasting a dry process bean with
a longer than normal profile could lead to a runaway unless you have an
active temperature control method.
My roasts are normally in the 95 to 105 gram range. This small batch size,
light weight drum, and 50 rpm rotation insures good temperature control.
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volume
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6) From: John Despres
Ken,
I think I may have lost track - are you still talking about the Gene 
Cafe here? If so, have you figured out a way to determine bean temp 
inside the moving drum? If you're not talking GC, well,  never mind...
John
Ken Mary wrote:
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-- 
John A C Despres
Hug your kids
616.437.9182http://www.sceneitallproductions.com

7) From: Ken Mary
John,
The same theory applies to the Gene Cafe. Although you cannot measure bean
temperature in a GC, you can use either timing or the GC's temperature to
profile roast. In my experience, drum roast profiling is easy. I have one
profile where the same heat setting is used from startup to shutdown. At
most I use 3 different heat settings. The drum and oven moderate the heat
that reaches the beans allowing for near linear ramps in the roasting
phases.
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