[Homeroast] Jimma

Yakster yakster at gmail.com
Thu Oct 14 12:44:43 CDT 2010

For understanding the Behmor profiles, nothing beats Ira's BehmorThing
program available on www.behmorthing.com.  I use it to plan and track my
roasts and greens inventory, it's invaluable if you're trying to get a P2
temp drop to occur at a given time (though I almost never use a P2 profile
anymore myself and now just open the door to cool things down).  Also, never
walk away from the Behmor during the roast... it may be tempting because
it's pre-programmed, but the results could be disastrous.

I'll keep this somewhat on-topic by using my Jimma roast profile as an
example in this email.

Since the Behmor doesn't have a temperature display, it's hard to talk about
temperatures.  It's also going to depend on the voltage available during the
roast which can affect the heat output.  It's also going to vary depending
on where you measure the temperature in the Behmor because of the air

The following picture is a roast graph of my roast of the Jimma, I roasted a
full pound on a 1# P3 B profile which I ended up extending the time on to
reach my desired roast.  It took quite a while to take the full pound to
first crack, the coffee is tasting very good now but I may roast my next
batch with a P1 profile which is full power throughout the roast.  I have a
thermocouple taped along the bottom of my roaster that's positioned about
one quarter inch below the bottom heating element to give me a good idea of
the heat output of the roaster during the roast.  I don't have a Bean
Temperature thermocouple installed yet.


You can see that even though the profile (blue line) shows a stepped roast,
the heat ramps up and is not instantaneous.  I pre-heated the Behmor and
old-style chaff tray for one minute on a P1 profile before putting in the
beans and starting the roast, so the drop-in temp is about 200 degrees.  Be
careful not to pre-heat too long (more then about 2 minutes) or the roaster
will not restart after stopping it, and wear Ove Gloves or other protection
for your hands.

The hump at about 8 minutes in is when the afterburner and fans kick in for
smoke reduction.  The green bar at the bottom indicates when I started and
stopped controlling the temp by opening and shutting the door.  I started
early, probably too early, to kill some of the momentum going into first
crack.  I watch the temperature and listen to the roast while adjusting the
door position to get the temps where I want them.  The olive box indicates
the start and end of first crack.  Finally, the dip at about 25 minutes is
when I stopped the roaster and pulled the beans to quickly cool them in my
bean cooler.  I let the Behmor take care of the cooling in the beginning as
it's pretty good at getting hte temps down to start with, but when the temps
drop low enough I pull the drum and restart the cool cycle while cooling the
beans myself.  Here's a picture of the beans cooling:


I'm not posting this information to be held up as an ideal roast, it's not.
This is pretty much a generic roast profile for me that I use for a lot of
beans as a starting point that works well for espresso and brewed coffee
most of the time.  It may be sacrilegious, but I've actually been using
profiles that take longer to get to first then the experts recommend on a
regular basis and been very happy with the results, especially when I get a
full pound of beans out of the roast in one batch to brew for the week.  I
look at the Quest roaster and it looks really nice, pretty much the opposite
of the Behmor with full manual control, but I don't know if I'd be happy
with 200 gram roasts.  I've gotten to like being able to come home and roast
a pound of coffee at night, but I know a more hands-on roaster would help
develop my roasting skills.  I think next time, as I said, I'll use a P1
profile and open the door to control entry into first crack with my next
Jimma roast.

Also note that this is a roast of a full pound of beans.  As such, things
ramp slower and the beans gain more momentum.  I can open the door during
first crack on full pound roasts and see the temperature hold steady with
the door fully open.  With a smaller batch, you'll get to first much quicker
and the bean mass won't hold the heat so much.

Hopefully this information will help others understand how the Behmor works
and how the profiles work, that's the intention anyway.


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