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Topic: New roaster advice - dropping temperature & specific bean questions (9 msgs / 652 lines)
1) From: John McPhail
Hello, I've been gleaning knowledge for several weeks in lurk mode  
and finally have a couple of questions of my own, so... time to post.  
I'm a new roaster and still feeling my way around, learning what my  
beans are telling me, and using a Gene Cafe. The coffee I'm roasting  
has been very drinkable but I want to learn more.
The roasting questions:
I see many, many mentions of dropping the temperature at first crack  
to prolong the time to the end of the roast to something around 4  
minutes. Do you drop the temperature when first crack starts,  
sometime during first crack, or when first crack finishes? I've tried  
a few different ways and end up with flat, hollow tasting roasts with  
poor aroma. A corollary question is - how far to drop temperature?
I'm guessing the the true answer is "it depends", but a rough rule of  
thumb and why it works might get me in the ballpark. My best-tasting  
roasts ( to my untrained palate ) have been using a straight  
temperature all the way through - they've had a good "snap" that I  
find missing when I've tried to drop the temperature. But if they can  
be better, I want to learn!
The bean questions:
I have some wet process Oromia Yirgacheffe that is giving me problems  
- it seems like a dense bean and should take a lot of heat, but it  
gets SO dark that I feel like I'm burning it. Not tipping, but all- 
over darkness on the bean. I aim for sometime soon after first crack  
on this bean. I'm also worried about how dark the bean is and the  
"tiger stripe" effect of the un-oily, light-colored seam on the dark  
bean. It just seems wrong somehow, but is it really OK? The beans are  
evenly dark but seem too dark, and the seams are uniformly light. I  
just have no idea where I am with this bean.
Peaberry - is there a general strategy for peaberry? I know that my  
Kenya peaberry is high-grown and dense, so it can take a lot of heat.  
I also know that since they're smaller and round they absorb less  
heat in general, but is that true for a roaster like the Gene Cafe?  
Finally, I know that since they're smaller they burn easier.
I'm just balled up thinking about the peaberry and the Yirgacheffe  
and appreciate any advice you have.
Lots to learn, I know, and trying to soak it up. Thanks everybody!
John McPhail
jmcphail

2) From: John McPhail
I forgot to mention that I've been roasting an even 8oz. per batch.
John McPhail
jmcphail
On May 31, 2006, at 7:25 PM, John McPhail wrote:
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3) From: Peter Schmidt
John,
W/o wanting to speak for others, I think what was meant by dropping temps
was lowering the heat output of the roaster, not lower the temp of the
beans.  Stalling or falling bean temps during 1st crack is a no-no.
I use a SC/TO w/ a digital thermo probe, and what I generally shoot for is
something like this;
Ascertain the temps at start of 1st, during rolling 1st, let it climb up and
taper off around 20 higher than the onset, or 10 higher than rolling 1st,
and then hold it there for a couple minutes.
So say I hear the first few cracks at 410, and it's going strong at 420,
I'll let it ease up to 430, and hold it there a bit.  If I want something
bright and light at City roast leve, I'll go by sound and stop when there's
no more than a stray crack.  And if I want to develop a tad more body for a
FC roast level, I'll give it a couple 2 or 4 minutes letting the temps creep
up to 435.
My spacer with the open/close flap allows me to keep temps fairly close to
where I want them.
I don't know how much of this applies to the Gene Cafe, but hope it helps.
peter schmidt
<Snip>
unsvbscribes) go tohttp://sweetmarias.com/maillistinfo.html#personalsettings

4) From: Don Cummings
Where is your probe in this process. In the air flow or bean mass?  Have yo=
u
punched through the bottom of the SC with the probe?
On 5/31/06, Peter Schmidt  wrote:
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-- 
Don

5) From: Peter Schmidt
This is a multi-part message in MIME format.
My thermometer is a BBQ meat grilling unit, and the probe is 6" pointy =
metal.  I have my spacer notched so that the probe dangles into the =
roaster w/ the tip submerged in the beans.  It gives a close reading to =
the actual bean surface temp.  I'll try to get some pics online =
tomorrow.
Before going with this thermometer, I had one w/ a K type thermocouple, =
and had a hole drilled in the side of the SC w/ a tube in that hole to =
facillitate threading the wire into the bean mass.  That worked o.k., =
but the beans beat up the wire and its insulation pretty bad, and it =
would move the bead around resulting in varying readings.
Some have screwed the TC bead onto the bed of the SC.  Someone on the =
list used the disabled thermostat to wedge the TC bead into place.  I =
imagine that works well, but would limit the SC's mobility for dumping =
the beans.

6) From: Don Cummings
How big are the batches you are doing? My tip does hit the bean mass but
only barely or it gets caught up in the stir arms.  I plan on drilling a
hole in the bottom of the SC bed and popping just the tip of a k-type TC
through to get a better idea of bean mass temp.  I'll probably mount the
meter to the side of the SC.
I don't believe I am reading much bean much mass temp and am getting mostly
air temp.
I have asked many people this today and no one has answered this question
yet.  Do you pre-heat?  I feel like I am getting flatter roasts with my
SC/TO than I did with my Whirly-pop.  I am wondering if I am actually takin=
g
too long to hit target, i.e. 18 mins or so to FC+.  I know this time is in
line with what other people mention but like I said my roasts seem a tad
flat in comparison. The aromatics as well.
On 5/31/06, Peter Schmidt  wrote:
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-- 
Don

7) From: Steven Van Dyke
Hi John!
I've had really good results with the last few roasts in my GeneCafe using
the same 'profile'.
I've started setting it for 482 / 20 minutes at the start.  The 482 is just
to get things going and the 20 minutes is to make it easier to track times.
I'm sure you've noticed the significant lag between the exit air temperature
(what you see on the display) and the actual bean temperature in the early
stages.  That's why I start with it set to 'max' (482).
My basic 'profile' is: set 482 / 20 minutes.  At the first sign of First
Crack I crank the temp setting down to 456 and start watching the output air
for the smoke puffs you get right before you get to Second Crack.  That's
when I hit the 'cool' button.
I'm finding it takes about 10 minutes to hit First.  I've mentioned before
that, for me, it's hard to hear First Crack over the sounds of the beans
sliding around and clicking off each other so I have to bend over and listen
by the gap in the 'safety cover'.  Interestingly, I'm tending to see the
output air temperature be right about the 456 I drop it down to at First
Crack.
It's taking about 4 minutes to go through First to the edge of Second (the
Full City+ Tom recommends for most of the coffees I get).  With my CafeRosto
I'd listen for the first snaps and cool then.  With the greater lag of the
GeneCafe I have to be a bit more proactive so I use a flashlight to watch
the column of air coming out of the chaff collector.  Right before you hit
Second Crack there's a sudden increase in smoke output.  During First Crack
you'll get smoke accumulating from the GeneCafe but it's really hard to see
it coming out of the chaff collector.  Right as you get into the Full City /
FC+ range you start seeing the smoke come out (at least when you use a
flashlight to highlight it).  That's when I hit to Cool button.
Some things I've found to speed the cooling:
1) Open the 'safety cover'.  It helps hold in the heat during the roast so
it makes sense to let it out now.
2) Jim had the great idea of pulling the air through faster.  He used a shop
vac, I just tried using a handheld vac.  Dropped below 300 in just under 2
minutes but didn't have much effect overall because I had to pull the vac
away to cool it.
3) Pulling the chaff collector off during cooling will increase the air flow
but does tend to create a bit of a mess.
I need to play with making a fan to sit over the chaff collector and pull
the air through at high speed.  Something like a metal triangle open on one
side and the opposite 'point' with a high-volume squirrel cage fan.
Enjoy!
Steve :->

8) From: Peter Schmidt
This is a multi-part message in MIME format.
Don, batches vary from 150g to 400+.  For a while I had my K type probe =
clamped so it would dangle into the beans.  That got to be a PITA, so I =
drilled a hole in the side of the SC and put a small tube through which =
I would thread the probe.  This also was a PITA, as the beans would push =
the bead around, and the temps would fluctuate.  I since switched to a =
BBQ thermo w/ a metal probe.
I only preheat on the initial roast, w/ both the top and bottom heat.  =
Once the greens are in, the bottom goes off, and approx. 3 minutes later =
the beans are at 300F.  They stay around 300-350F for 3-5 minutes, then =
are ramped up to 1st crack (with top heat only).  So, 1st crack arrives =
6-8 minutes after the beans go into the roaster.  If 1st crack lasts for =
2 min., and the beans stay at that temp or inch up for another 2-3 min., =
then the total time is 12-14 minutes.
The flatness you're getting may be from a more drawn-out roast.  SC/TO's =
can mimic the smoothness of drum roasts, or the liveliness of your =
whirly.  I'd suggest speeding your roast up a tad.  Don't rush to 1st; =
let the beans stablize for a bit.
I've got a few pics, and a few details here;  =http://peter4jc.googlepages.com/I hoped that helps a little,
peter schmidt
  How big are the batches you are doing? My tip does hit the bean mass =
but only barely or it gets caught up in the stir arms.  I plan on =
drilling a hole in the bottom of the SC bed and popping just the tip of =
a k-type TC through to get a better idea of bean mass temp.  I'll =
probably mount the meter to the side of the SC. 
  I don't believe I am reading much bean much mass temp and am getting =
mostly air temp.
  I have asked many people this today and no one has answered this =
question yet.  Do you pre-heat?  I feel like I am getting flatter roasts =
with my SC/TO than I did with my Whirly-pop.  I am wondering if I am =
actually taking too long to hit target, i.e. 18 mins or so to FC+.  I =
know this time is in line with what other people mention but like I said =
my roasts seem a tad flat in comparison. The aromatics as well. 
   
  On 5/31/06, Peter Schmidt  wrote: 
    My thermometer is a BBQ meat grilling unit, and the probe is 6" =
pointy metal.  I have my spacer notched so that the probe dangles into =
the roaster w/ the tip submerged in the beans.  It gives a close reading =
to the actual bean surface temp.  I'll try to get some pics online =
tomorrow. 
    Before going with this thermometer, I had one w/ a K type =
thermocouple, and had a hole drilled in the side of the SC w/ a tube in =
that hole to facillitate threading the wire into the bean mass.  That =
worked o.k., but the beans beat up the wire and its insulation pretty =
bad, and it would move the bead around resulting in varying readings.
    Some have screwed the TC bead onto the bed of the SC.  Someone on =
the list used the disabled thermostat to wedge the TC bead into place.  =
I imagine that works well, but would limit the SC's mobility for dumping =
the beans.

9) From: raymanowen
Don, if you put "a hole in the bottom of the SC bed and popping just the tip
of a k-type TC through to get a better idea of bean mass temp." :
Imagine the tip of a tc sitting there. It's just the junction of the
Chromel/ Alumel wires that comprise a type K thermocouple.
It's really Not a good set-up. The junction develops the TC potential which
varies directly with its temperature. The TC meter is just a voltmeter
calibrated to read out in degrees F or C.
The TC junction is being heated by the process in which it's immersed, and
you'll read the actual temperature of that junction, in spite of what you
think you're reading.
The lead wires are cool, and they will be pulling heat away from the
junction. Who keeps the lead wires hot? By design, You do- if you want
accuracy.
Your meter is telling you exactly how hot the junction is.
The junction is rapidly losing heat to the cool lead wires- a low thermal
impedance heat sink- so the temperature of the junction is much more closely
associated with the temperature of the cool lead wires than the coffee beans
or hot air in the roasting chamber.
If you are simultaneously adding and subtracting heat to the junction, as is
always the case, which process is winning and to what extent? Therein lies
the error of temperature measurement.
The junction is the point of contact between two wires, so your digital
meter is telling you the temperature of the wires, nothing else. If you keep
the wires away from the heat, they cool the junction. The meter doesn't know
or care- it's indicating the temperature of the junction.
Cheers -RayO, aka Opa!
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