HomeRoast Digest


Topic: Strange smoke behavior in new roaster (23 msgs / 341 lines)
1) From: Jim Gundlach
I've been working on a roaster using a Sunpentown turbo oven with a  
1500 watt micro carbon fiber heating element on a set of nested  
stainless steel bowls which are in turn  mounted on a modified bread  
machine that takes care of stirring.  This roaster is relatively air  
tight and and the turbo oven unit has a glass top so I can see the  
beans during roasting.  I expected the roasting chamber to fill with  
smoke as the roast progressed through the end of the first crack but I  
find that does not happen.  In fact, the only thing that obstructs any  
view of the beans at all is the chaff.  However, and this is what I  
find strange and don't understand,  when I lift the turbo oven off the  
bowls, the hot air leaving the roaster turns smoky and as far as I can  
tell the interior of the roaster stays smoke free.  Has anyone seen  
anything similar and can anyone explain it?
      pecan jim

2) From: Rich
Lack of oxygen with lid on.
Jim Gundlach wrote:
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3) From: Alchemist John
As a matter of fact, I noticed that with my Zen II a few weeks ago 
when I replaced one of my tubular heaters with a pair of halogen 
lights, giving me vast amounts of light.  What I discovered was from 
a visual standpoint, smoke seemed to be ENTERING the roasting chamber 
from the bottom and then leaving at the top.  What I translate this 
to is that smoke requires oxygen and when fresh oxygen was leaking 
in, smoke was instantly created.  I immediately sealed the wholes and 
my smoke production dropped off a good 75% (I still have exit leaks 
where smoke is created).  Now I see just what you are - no smoke 
inside the chamber, but as soon as roasting "vapors" hit the air, 
smoke is formed.
At 18:17 11/6/2007, you wrote:
<Snip>
John Nanci
AlChemist at large
Zen Roasting , Blending & Espresso pulling by Gestalthttp://www.chocolatealchemy.com/

4) From: Floyd Lozano
You see something is there, but what is it?  I'd always assumed the smoke
you see is from burning chaff, but you say you don't see smoke IN the
chamber, only at the periphery where air enters and leaves, and this points
to something gaseous or very small (non naked eye visible) particulate
matter being lofted about by the hot air.  Curious!
-F
On 11/6/07, Alchemist John  wrote:
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5) From: Cameron Forde
My hunch is that it is the moisture in the air and not the oxygen that
is responsible.  Coffee roasting liberates a bunch of organic acids
that will bind water in the air and form larger particulates (smoke).
Cameron
On 11/6/07, Floyd Lozano  wrote:
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-- 
ceforde

6) From: Homeroaster
Visible smoke is particulates mixed with invisible gasses.  Not much magic 
changes that.
Obviously there is plenty of air pumped in by the Sunpentown unit, so it's 
not a lack of air/instant combustion thing.
I'd guess the smoke is obscured until it is out in the open where the 
contrast is greater.
I can't see dust in my living room until the evening sun skims across the 
hardwood floor.  Then it's in the air, on the floor and I can either pull 
the shades over the atrium doors or I can clean.
*********************
Ed Needham
"to absurdity and beyond!"http://www.homeroaster.com*********************

7) From: Edward Bourgeois
Jim  I have similar setups. Do you have pics of your roaster? I
believe it's the lack of introduced oxygen. Notice when you take the
top off you get a plume of smoke. Here are pics of my setupshttp://coffee-roasting.blogspot.com/On Nov 6, 2007 9:17 PM, Jim Gundlach  wrote:
<Snip>

8) From: Edward Bourgeois
Ed Turbo oven tops dont bring in outside air. There are two fans. The
lower, around the heater has no vents, the upper is vented and keeps
the motor and stuff in the top cooled.
On Nov 7, 2007 1:12 AM, Homeroaster  wrote:
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9) From: Edward Bourgeois
Jim  I got a sunpentown nano carbon fiber top to try and I like the
heat up speed but it's only 1200 watts and cant do the quantity that
my galloping gourmet 1470watt top can. I split the fan and heating
element wiring on my tops and run the heater into a Kill A Watt meter
into a variac and really like how it works. Ed B.
On Nov 7, 2007 1:20 AM, Edward Bourgeois  wrote:
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10) From: Sean Cary
I thought the same thing - once it escapes from the darker chamber
into a space with more contrast?
I see more smoke with my SC/TO then with my Dhabolten popper - that
escapes explanation since the popper has more light all the time and
you would think you would see more smoke - but also MUCH more chaff
escapes before it can smoke.
In Comm gear the magic blue smoke hides in the wire...
Sean
92.75
On Nov 7, 2007 9:12 AM, Homeroaster  wrote:
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11) From: Gary Townsend
On Nov 7, 2007 12:33 AM, Sean Cary  wrote:
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12) From: Alchemist John
Did you have something Gary  :)
Nope - whereas I can't nail down EXACTLY what it is, contrast it 
isn't.  The smoke I see is coming from a super well lit interior 
(1000 W of halogen light) with good interior contrast to a dimmer 
exterior. In can see motes of dust and debris inside swirling around, 
but no smoke. I can literally see the smoke form an inch or so away 
from the roaster.  The roasting vapors are defiantly condensing into 
smoke upon leaving.
At 04:54 11/7/2007, Gary wrote:
<Snip>
John Nanci
AlChemist at large
Zen Roasting , Blending & Espresso pulling by Gestalthttp://www.chocolatealchemy.com/

13) From: Rich
If you have adequate temperature and excess oxygen, you will have 
complete combustion without smoke.  Look at the gas stove.  Now, if you 
have temperature and very low oxygen you will have no combustion but the 
combustible material will decompose from the heat into combustible gas. 
   This gas will combine with available oxygen without visible smoke. 
When you open the lid and admit excess oxygen to a concentration above 
that required to initiate combustion you will see smoke because you are 
at the minimum level to initiate clean combustion at all of the various 
bean surfaces.  Briskly stir the beans and the smoke will decrease, but 
you may get flame also..
Alchemist John wrote:
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14) From: Gary Townsend
Must be old age, John...can't remember what I was thinking of ;-)
On Nov 7, 2007 7:11 AM, Alchemist John  wrote:
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15) From: Jim Gundlach
On Nov 7, 2007, at 7:32 AM, Rich wrote:
<Snip>
The beans are briskly stirring all the time but I am no where near  
third crack temps.
     pecan jim

16) From: Rich
I was talking about stirring them after opening the roaster at the end 
of the roast.  Wood decomposes into combustible material when heated. 
It is these decomposition products that burn.  If the O2 is not 
sufficient, you get incomplete combustion and smoke. If the O2 is lower 
still there is no combustion.
Jim Gundlach wrote:
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17) From: Homeroaster
There is likely a component of steam too, since it's a fairly closed 
environment and the significant moisture has to go somewhere.  I know you 
know the difference between smoke and steam, but adding an unseen steam 
component might accentuate the smoke upon opening the lid.
*********************
Ed Needham
"to absurdity and beyond!"http://www.homeroaster.com*********************

18) From: Edward Bourgeois
I think there is something to do with temp contrast. Hot air/gases
that escape the roast hit cooler air and condense into visible smoke.
Same as steam coming out of a storm drain on a cold morning.
On Nov 7, 2007 9:51 AM, Rich  wrote:
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19) From: Rich
Water vapor at less than boiling is visible.  Steam, water in the 
gaseous state, however is invisible.  The condensed steam will appear, 
or become visible, when it cools to less than 212.
Homeroaster wrote:
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20) From: Homeroaster
I wasn't using the term steam in any technical fashion.  Just steam, as we 
all know it, water vapor, hot or cool, suspended in the air, which most 
would say is visible.
*********************
Ed Needham
"to absurdity and beyond!"http://www.homeroaster.com*********************

21) From: Homeroaster
If I would have thought for a second, I think I could have figured out how 
wrong I was, thinking the turbo oven blows in air.
*********************
Ed Needham
"to absurdity and beyond!"http://www.homeroaster.com*********************

22) From: Rich
I suspected that was the case.  But at the end of a roast cycle the poor 
little bean has been at a temperature in excess of 212 degrees for 
several minutes.  I suspect that it has boiled dry by now.  I would 
expect that the steam has purged the O2 from the roast chamber before 
the bean has heated to the point of combustion.  You will not see the 
steam.  The only thing that burns is the chaff when I use a heat gun to 
roast in an open deep bowl.  And not much of that chaff burns either.
Homeroaster wrote:
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23) From: Rich
I blow hot (750 degree) air into the bowl when roasting and there is no 
smoke until the very end and not much then. I roast to FC or a little 
more and most of the smoke occurs after the gun is off.
Homeroaster wrote:
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