HomeRoast Digest

Topic: Air Quenching (30 msgs / 578 lines)
1) From: EskWIRED
I've heard the opinion that it is crucial to arrest the roast and cool the
roasted beans as quickly as possible.
I've heard that air quenching is inadequate, unless it is done very
efficiently, and that water mist quenching makes for a very superior cup
(altho I've never tried it).
Does anybody here have any strong opinions?  Is it really necessary to
arrest the roast instantly, and to get the beans down to (what temperature?)
within seconds?
Lately, I've been simply switching off the heater on my modified Popcorn
Pumper, and cranking the fan up to maximum velocity to cool the beans.  Very
easy, and the beans cool to <100F within a minute or two.  They fly way up
into the hurricane lamp chimney, with lots of air all around them.
But would I get better results if I were to spill the beans and cool them to
ambient within seconds, instead of a minute or two?
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2) From: Dan Bollinger
Spilling the beans wouldn't be faster than using forced air unless you
spilled them onto a cooled surface or misted them immediately.  Dan
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3) From: Gary Zimmerman
Ted Kostek wrote:
The most critical thing is consistent technique, if you're doing 
comparisons or trying for repeatability.
The beans will continue to roast for a bit after you remove them from the 
heat.  It's best to cool quickly (but without using a technique that 
results in water condennsed on the beans).  I tried air quenching, but was 
not happy with the results.  Hard for me to resist the temptation to over 
spray, and water is probably as "deadly" as oxygen to the preservation of 
roasted beans.
I moved to pouring the beans back and forth between a mesh colander to a 
mesh strainer outside my front door.  That didn't always cool quick enough 
for me. (I'd say they should be mostly cooler within about 30 seconds, and 
cool enough to stick your hand in within a minute.)  That technique did 
have the advantage of de-chaffing, since I roast in a stovetop popcorn 
popper pot.
Finally, I moved to my current "technique" which still involves the 
strainer and colander, but I've added a small plug-in fan to the mix.  I 
set up the fan runnin outside my front door, pointing upwards before I 
begin the roast.  When the roast is done, I pour the beans into my 
strainer, grab the colander, go outside quickly, and hold the strainer over 
the fan.  Much of the chaff blows off (and all over everything and 
me).  Then I move the colander over the fan, and pour the beans into 
that.  I may pour back and forth a few times, but the beans end up in the 
wire-mesh colander, with my hand stirring the beans over the fan until 
they're near to ambient temp.  Takes a couple of minutes only usually, 
depending on how darkly I roasted the beans.
The list has had several discussions of cooling in the past, so you might 
find some info in the archives, but I'm sure the current listies will have 
some opinions too.
Probably not too much better.  Again, just make sure your technique is 
consistent between batches.
-- garyZ
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4) From: Gary Zimmerman
Gary Zimmerman wrote:
Oops.  Fingers flying before I finished my morning cup.  That should have 
been "I tried WATER quenching, but was not happy with the results." --gZ
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5) From: wizg
[Sorry! I left out the Subject header on my previous reply.]
Except for a small amount of chaff left over from the air-popper roasting 
blowing about, I like a variation of this method whereby I substitute an
active air conditioner vent for the fan.
At 11:53 AM 8/12/02 -0700, you wrote:
 about a minute.  My own experiences (read: mistakes) have shown that
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6) From: Anthony Ottman
It is important to cool the beans as quickly as possible, but for the
size batches we do, water cooling is unnecessary.  
My technique is similar to Gary Z's, I dump the beans into a fryer basket
and shake it to circulate the beans in front of a Vornado (tm) electric
fan.  Lots of airflow de-chaffs and cools up to a half-pound or so within
about a minute.  My own experiences (read: mistakes) have shown that
slow cooling does bad things to flavor.
Anthony Ottman
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7) From: EskWIRED
That's pretty much what I figured.  Before I put a cutoff switch on the
heater, I used to spill them into a colander and stir.  It seems like the
two are about equal.  What bugs me is that air is such a lousy conductor of
heat.  The saving grace of the forced air seems to be that there is so much
of it, it can carry a lot of heat, despite it being basically an insulator.
I've been thinking about keeping a slab of marble or a pizza stone in the
freezer, and spilling the beans out onto it.  But since heat rises and cold
sinks, I'm thinking that would be of little help, unless the stone went on
top of the beans.  I wonder if there's some kind of massive compliant
material which could be laid out on top of the beans, and which would soak
up their heat instantly?  Maybe a sandbag type of thing?  Filled with
marbles?  I dunno, but it seems like it might be fun to try it.
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8) From: Gary Zimmerman
EskWIRED wrote:
Aluminum foil?  It cools quickly.  Maybe pour the beans out onto a loose 
sheet of foil, fold and pat the foil over the top, then aim a fan at 
it?  The whole process may end up slower than any of the less involved 
methods, though.
Before I used a fan, I'd pour the beans onto a frozen pizza pan after 
tossing the beans between strainer and colander for a few minutes, to take 
them down the final way.  But you have to be careful when using anything 
from the freezer about condensation getting moisture on the beans.  The fan 
works best for me now.
-- garyZ
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9) From: EskWIRED
  But you have to be careful when 
Yeah, I can see that. 
Frozen equipment would have to be reserved for those low dew point days. :)
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10) From: Dan Bollinger
Why not lay an insulating towel over the top?  This would limit the heat
from only the beans to enter the stone instead of the heat from the beans
AND the surrounding air in the room. The chilled stone would cool the beans
by conductance and cool the beans through convection with the now chilled
air.  You'd have to give it a try and see if it was faster.
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11) From: Ed Needham
Not sure where you heard that water quenching makes for superior coffee, but
I really don't believe it is anywhere near the truth.  I think most would
agree that adding moisture to the beans may even be harmful unless it
evaporates immediately.  Even then, I see no need to water mist in small
The intent is to cool the beans so roasting is arrested at a particular roast
point.  If you are cooling a full 135 pound bag of beans, aggressive measures
need to be taken to assure you don't lose the whole roast because the beans
continued to roast past where you wanted them to stop.  Commercial roasters
utilize stirring and large volumes of air to quench the beans.  I've seen
some mist water over the beans when they are blistering hot and it evaporates
to vapor immediately.  It is not something used to improve the roast.  It's
used to stop the progression of the roast.
For homeroasters though, we are talking about cooling one pound "tops", and
it is really not that hard to do that.   Cooling it enough so that the roast
stops can probably occur in a minute with agitation and a fan.  Let's not get
carried away with techniques large commercial roasters use and assume they
impart some kind of special quality to the beans.  If the beans can be cooled
to touch in a few minutes, that's all that's necessary.
Ed Needham

12) From: Gary Zimmerman
Ed Needham wrote:
I think that part of the interest in water quenching comes from Kenneth 
Davids's book.  That was the only book I read on home roasting, and it was 
the first place I ever heard of the technique, so I tried it when I started 
home roasting.
He does caution home roasters not to use too much water - to just mist the 
beans right away with a small enough amount that the water vaporizes 
completely, but I found it was difficult to do that in practice.  I just 
didn't trust that I was misting lightly enough, but at the same time, I 
didn't think lighter misting would have any appreciable cooling effect.  So 
I gave up on it.
I didn't really pay attention (nor have enough experience with home 
roasting, nor do any experiments) at that point to note whether there was a 
dramatic improvement in flavor after I stopped with the water.
-- garyZ
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13) From: Andrew Thomas
--- "EskWIRED"  wrote:
If you are cooling your roast to less than 100F within 2 minutes, I think the way you are doing it is plenty good enough. And easy too!
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14) From: EskWIRED
Bingo.  In my case, anyhow.
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15) From: Photogal1966
Regarding all this bean cooling discussion, I was just wondering if anyone 
else here uses a coffee cooling mat?
A dear friend and coworker of mine gave me one. It is tightly woven and about 
12 inches in diameter. They are traditionally used in her homeland of Eritrea 
(which I know spelled wrong ... sorry) in Africa as part of the coffee 
roasting hospitality ceremony.
Works very, very well.
Anyone else ever seen one?
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16) From: EskWIRED
It is easy.  That's one reason I wasn't sure it was good enough. It seemed
almost too easy.
The metal parts of the roast chamber seem to stay hotter than the beans, so
if I turn off the fan, I need to dump it without too much delay.  If I'm
doing my last batch, I turn it back on after dumping it, with just the fan
going, to cool down the metal parts.
I did a couple of roasts this afternoon of Kenya AA.  One to light city, and
the other to a very full, rolling, second crack city.  I went darker with
the second one than I usually do, to check out how long it took to cool.  It
was hot and sweaty today, so it took somewhat longer than usual, but it went
to 200 in a minute and a half or so. I'm pretty glad I added the switches
and dials and stuff to the PP.  I've got a 1400w model in the wings, but
I've heard that the heavy cast parts make it hard to get the temp down
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17) From: Ed Needham
Quick...Buy stock in coffee cooling mats!
Ed Needham

18) From: Charlie Herlihy
 Gary Zimmerman wrote>I think that part of the
interest in water quenching comes from Kenneth 
Davids's book.  That was the only book I read on home
roasting, and it 
the first place I ever heard of the technique, so I
tried it when I 
home roasting.
  I could get flamed for this but-Ken's book, which is
still the only one I know about out there, is just a
beginers' primmer for home roasting. There has been a
lot of progress from people sharing their experiances
through this forum and others since Home Coffee
Roasting Romance and Revival was published. Ways of
profiling roasts instead of single (high) temperature
roasting being a major improvement. Having said that,
I seem to recall (I lent that book to someone) that
Ken Davids did warn about using more than a brief
misting to start cooling. Comercial roasters who water
quench don't often mention that the weight of the
water is a significant factor in using that system.
Quickly clearing the roasting area for more production
being another. My strong opinion is that if any water
enters the beans flavor does suffer, and noticably.
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19) From: Andrew Thomas
--- Photogal1966 wrote:
I've never heard of it, but it sounds interesting. What is it made of and how is it traditionally used?
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20) From: Photogal1966
The traditional use of the mat, from what I understand, is just to dump the 
hot beans on and spread them out.
It is hand woven and flexible. Does come in handy for getting the cooled 
beans into jars.
Not sure if this black and white pic I took some time ago will help, but here 
it is:
[Unable to display image]

21) From: Les & Becky
I have had the pleasure of partaking in the Eritrea (your spelling was
correct) coffee roasting hospitality ceremony.   I participated weekly for
26 weeks!  When I was working on my degree in Linguistics, I had a UN grant
to develop language learning tools for UNICEF workers going there for famine
relief.  I had 22 of the most beautiful African women, and one fine
gentleman as my language informants.  Being single at the time, I found it
most unfortunate that all 22 women were married to ex US service personnel
that had been stationed there.  I would love to have one of those cooling
I tried misting and it is too hard not to get your beans too wet!  I much
prefer the winnowing method, or a colander and a fan.

22) From: Photogal1966
You mean I can spell? Will wonders never cease. Sounds like you had a 
wonderful time in Eritrea. Great place to enjoy coffee, I bet!
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23) From: Les & Becky
Unfortunately, I wasn't part of the team that got to go to Eritrea!  The
native language informants that I worked with lived in the Minneapolis,
St.Paul, MN area.  However, I did get to spend time in Benin,  West Africa
working on an Anthroplogy project, so don't feel too sorry for me.

24) From: AlChemist John
Sometime around 13:07 8/12/02, EskWIRED typed:
This is what I do and I find it works nicely.
HUH?  That is not a truism for all materials, especially most solids.  Hot 
gases rise because they are less dense and hot liquids (water ) 
likewise.  But then again, cold ice rises, not because it is cold, but 
because it is less dense than the water.  If you are cooling by surface to 
surface contact, whether the hot item is up or down does not make a 
difference.  Heat is not affected by gravity, but hot items can be.
Regardless, as others have said, we are cooling a very small quantity of 
beans.  I have noticed very little if any difference in a 1 minute cool 
down as opposed to a 3-4 minute cool down.
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
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25) From: EskWIRED
Damn.  That makes perfect sense, once I thought about it properly.  I always
thought "heat rises".  But that is not true.  "Some hot objects rise" is the
correct formulation.  Thanks.
But now you'll have to indulge me with my new found half-wisdom (please).
Would it be true that adding heat to any portion of a solid will change the
average temperature of the solid equally well (say a block of copper, for
ease of my conceptualization) if we have only conduction as the means of
exchanging the heat? (I realize that the radiation and convection  will play
a part, but I'm ignoring that).
So that, for example, putting my copper brick on top of a hotplate will work
no better than putting the hotplate on top of the brick? Wow.  I never
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26) From: Angelo
I used to dump my beans into a mesh strainer with pre-cooled marble and 
just mix them around...The problem with this is condensation and the pain 
in separating the beans from the marbles...
Now, I just reverse the window fan which was pulling the smoke and chaff 
out of the popper. It cools very quickly
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27) From: Dan Bollinger
Duck and Run!  Here I come!  :)     Contact area determines feat flow rate.
If the beans are laying on a hot plate, every bean has some contact with the
heated surface.  If the hot plate is on top, only the three tallest beans
are in contact with the hotplate (a plane is defined by three points).  You
now have enough information to determine which one will heat (or cool) the
fastest!  Dan
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28) From: AlChemist John
Sometime around 09:34 8/13/02, EskWIRED typed:
So long as you turn the hot plate upside down (duck and run (g)).  Really, 
it would heat the same ignoring the items you mentioned.  If you don't 
ignore those items and try to predict what would actually happen you would 
have to note that the brick will conduct heat to the counter it is sitting 
on making it heat slower. OTOH, the counter may well insulate the area and 
reflect heat back making it heat faster.
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
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29) From: Dan Bollinger
LOL!  Doesn't it though!?  ;)
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30) From: AlChemist John
Sometime around 19:03 8/14/02, Dan Bollinger typed:
I realize it is a coffee list but we were talking a theoretical brick with 
a flat surface.
In reality I would be VERY surprised if this were the case.  Beans are way 
too close in size that only three would touch.
What this has to do with practical coffee roasting or even cooling, I'm not 
really sure, but it makes for an "interesting " discussion .
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
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