If I'm comparing roast profiles with another Roaster roasting the same
beans with a differant setup, can we use the start of first crack as a
base point. Say my thermocouple placement records first start at 390*
and the other roaster at 402* can we basically adjust the 12* and then
compare(taking into consideration heat changes etc.) How much variance
in  the temp. of start of first crack with the same beans can there
be? Ed

Are you both using the same roast method and temp measuring setup?
I could see a possibility that if you were roasting HG/something with the
probe in the bean mass and they were using a drum with probe purely in the
air area that different temps might register for the same "event".
How about TIME to first crack? Is it similar for both of you? If you were
both using say HG/DB and one of you hit C1 earlier than the other, then the
faster one may have a higher air temp going to the beans.
Safe Journeys and Sweet Music
Justin Marquez (CYPRESS, TX)
On 7/2/07, Edward Bourgeois  wrote:
<Snip>

I would say that you could use 1st crack temps as base point only if you are
able to control all the other variables in the two different set ups. In my
experience, first crack can vary considerably depending upon batch weight,
bean prep and moisture content, and especially temperature ramp. The
absolute difference in temps is unimportant IF they are repeatable and
consistent.   Are the locations of the temp probes fixed and fairly stable
in the two set ups?
On 7/2/07, Justin Marquez  wrote:
<Snip>

So with using  the same beans in the same roaster an 8min roast to
first cr. or say a 10min. or 12min.roast to first cr. would record a
different bean temp at the point of start of first cr.? and if so by
generally how many degrees can it vary. Was hoping that first crack
for a specific bean lot would hit first crack at same bean temp. no
matter what type of roaster or times as long as the times were within
a couple mins +or- of each other. Then If our bean temp thermocouple
are both rather stable we could adjust using the first cr point as a
base line.
On 7/2/07, Robert Joslin  wrote:
<Snip>

On Mon, Jul 02, 2007 at 04:53:54PM -0400, Edward Bourgeois wrote:
<Snip>
In my (limited) experience, this is not the case at all.  Even in the
same roaster with the same probe in the same location and roasting the
same beans, I get a different 1C temperature depending on my profile.
If I ramp quickly, the temperature at first crack is higher than if I
ramp slowly.  This makes sense, as the temperature being measured by
my probe (which sits in the bean mass) is roughly the temperature of
the very outside of the bean -- and not even that, really, as much as
the air just outside of the beans.  First crack is probably more
influenced by internal bean temperature than outside temperature, and
the internal temperature is a function not only of the outside
temperature but of how quickly you got there.  A variation in time to
first crack of +/- a couple of minutes represents a pretty significant
difference in the profile, at least for the sort of roasting I do (hot
air popper), and so I would expect a difference in probed temperature
at first crack as well, with a higher probed temperature on the
shorter roast.
If you manage to get a reading where you each hit first crack at
roughly the same time using the same amount of the same bean, then the
temperature readings are probably comparable and can be used to
calibrate one against the other.

Yes, several degrees has been my experience.  Slower ramp cracks at lower
temps for me; although I'm still learning.
Maybe you should share beans from the same purchase and try it; they will be
similar age and moisture content.
John

My friend and I seem to be about 11* different. When we both buy the
same bean from Tom and aim for the same time we are from 10-12*
different and and when it's on the high or low side is usually the
difference in how we got there. thanks, Ed
On 7/2/07, John Moody  wrote:
<Snip>

I assume you are talking degrees F.  What roasters?
Can you trade temp sensors for a roast, or are they too different?
Or .... you could both buy the Behmor when it comes out. It has no temp
readout. :)
John

  You can't really measure the internal (inside the) bean temperature - all
probes will be measuring some averaging of surface bean temp and air temp,
most likely biased towards air temp.  First crack, in fact all of the
development phases of roasting for a given roaster, will depend on the
surrounding air temp, surface temp of the roasting surface if not a total
fluid-bed roaster, and the time spent at roasting temp (among other
parameters).  So a number of factors can contribute to seeing different temp
readings at 1st crack, including ramp time, starting bean and roaster temp,
ambient temp, and air circulation of the environment.
  I aim for consistency in my own roasting environment and fully expect the
numbers to vary from other environments, even with same bean, roaster,
ambient climate, and roasting profile.  Such is the nature of home roasting
with small roasters in non-uniform settings.
  But that's just my opinion - I could be wrong ...
Larry
On 7/2/07, Edward Bourgeois  wrote:
<Snip>

"Maybe you should share beans from the same purchase and try it; they will
be similar age and moisture content."
Or you could trip out to Oakland, and you and Tom roast equal quantities of
Gzornenblatt beans in the same roaster. There is hope that with some
mentoring from Tom, you could maybe match his roast. Then what? Who told Tom
how to do roast?
Cheers -RayO, aka Opa!
Do your own roast

Factors indeed.  Frying pan, oven, wok, grill, heatgun, steam, quartz
heaters; they will all cook a hamburger to a perfect 135F internal
temperature.  Not all will taste the same; just as coffee from different
style roasters.
John