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Which Heat Gun?
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Discussions > Coffee > Home Roast > Which Heat Gun?  
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MGLloyd
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Joined: 31 Oct 2002
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Posted Fri Jan 23, 2004, 1:17pm
Subject: Re: Which Heat Gun?
 

Based on the posts here and on alt.coffee and some emails I received when compiling the primer, it seems that 14 CFM seems to be a minimum to achieve an even roast while 27 CFM was too prone to blowing the beans out of the roasting vessel.  So my recommendation so far is greater than or equal to 14 CFM and less than 27 CFM.  Unless I am roasting only a cup, I almost always have to stir the bean mass, either with a utensil or with the barrel of the heat gun.  

It is too bad that CFM is not routinely printed on the heatgun box for comparison purposes.  I had to find the CFM figures from trolling the Net.

PS: I forgot to initially mention that stirring by airflow is also a function of the surface area of the roasting vessel.  I am doing some experiments with some vessels that are shaped more like cake pans, with straight sides.  As a matter of fact, I think an uncoated 8" or 9" cake pan that is 3 inches deep would be an excellent roasting vessel.  The problem is that if the surface area is too large, the bean mass is too shallow and not enough heat is retained, making it difficult to reach first crack.  I did a two cup by volume roast the other day in a 96 oz. heavyweight steel dish from Drs. Foster and Smith that is 9.5" in diameter by 2.75" deep.  The bean mass was about 2-4 beans thick, and I was able to stir this via airflow only from the start of the roast.  It seemed to work pretty well, but I need to repeat my results to make certain.

 
Regards,

Michael Lloyd
Mill Creek, Washington  USA
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Majnun
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Posted Fri Jan 23, 2004, 6:43pm
Subject: Re: Which Heat Gun?
 

In reference to the posts about uneven roasts, with some beans being light, what I've been doing is stirring constantly with a wood spoon in my left, and moving the gun around an inch over the beans with my right.  I've gotten a very even roast this way.  The only one that wasn't was my first (and first ever batch), where I don't think I stirred as much and heated up too quickly.   My gun, the Milwaukee HT220 /Wagner doesn't have a heavy air flow, so it doesn't move the beans much by air, and I just put it on the high heat setting.   So, perhaps the lower cfm and manual stirring helps give an even roast.  Just a thought.

-Tom
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ArabicaFueled
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Posted Fri Jan 23, 2004, 7:11pm
Subject: Re: Which Heat Gun?
 

WOW!  Spend a week working, and look what happens.  Has anyone got a current count on the number of heatgunners?  Seems like the community is growing pretty quickly.  Not a big surprise.  I guess the combination of low cost, immediate feedback, and fairly foolproof roasting of reasonably large batches is a pretty compelling combination.

Your bean agitation experiences sound a lot like mine.  I've got a gun that doesn't blow a huge volume of air, and I have to stir through the entire roast to keep it even.  I think that for those of us on the low end of the CFM and temp end of the spectrum are best served by:
 1) Stirring constantly
 2) Using a bbq grill to add heat and even things out

So, sad but true, I've got upgrade-itis.  I'm looking longingly at the posts of people who are blowing beans out of the dish :)

I just took a look at Ed Needham's site, and we haven't made it up there yet.  I assume that is what the primer that you're working on is for Michael?  If you need a hand with any content/pics, just let me know.

Todd M.
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MGLloyd
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Joined: 31 Oct 2002
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Posted Fri Jan 23, 2004, 8:03pm
Subject: Re: Which Heat Gun?
 

ArabicaFueled Said:

I just took a look at Ed Needham's site, and we haven't made it up there yet.  I assume that is what the primer that you're working on is for Michael?  If you need a hand with any content/pics, just let me know.

Todd M.

Posted January 23, 2004 link

You are correct, Todd.  I am leaving the primer up for about a week to ensure that people get a chance to see it and make comments or send me their suggestions.  I took a bunch of pictures today when I roasted two batches of espresso and a pound of drip.  When I do the second draft and send it to Ed, it will have the pictures on his site.  

I very much anticipate the primer will be a work in progress as we all gain experience and trade tips on equipment and technique.  I have gotten many good suggestions for changes on the draft currently posted.

 
Regards,

Michael Lloyd
Mill Creek, Washington  USA
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heatgunroast
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heatgunroast
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Posted Fri Jan 23, 2004, 9:02pm
Subject: Re: Which Heat Gun?
 

ArabicaFueled Said:

I've got a gun that doesn't blow a huge volume of air, and I have to stir through the entire roast to keep it even.  I think that for those of us on the low end of the CFM and temp end of the spectrum are best served by:
 1) Stirring constantly
 2) Using a bbq grill to add heat and even things out

So, sad but true, I've got upgrade-itis.  I'm looking longingly at the posts of people who are blowing beans out of the dish :)

Todd M.

Posted January 23, 2004 link

Reading Robo's discussion of heat transfer and air volume (on the primer thread) confirms what I've settled on through experience and explains a bit why I agree with Todd (or he agrees with me - - -who even knows anymore?).  
     IMO (got that? I said IMO  :o)    ) Stirring constantly is the best way to ensure an even roast (that, and allowing enough time before 1st c.) .  Using the heatgun to agitate beans is not.  At low CFM, it's necessary to get the gun nozzle right into or on top of the beans if you want a stirring effect.  I don't believe that the very high temp on the surface of the beans is a good idea (unless you stir like mad in which case, what's the point?).  At higher CFM, you start to experience the effect Rob noted of actually "removing" heat (well, sort of).  There is something "efficient" sounding about having the heatgun both heat and stir the beans, but when you think about it, what are ya going to do with the other hand anyway?  Now, it's entirely possible that Todd's gun is too wimpy- - -I don't know it.  But I'd sure avoid getting a blaster in hopes of roasting one-handed. (on the other hand, if it saves you from upgrade-itus making you want to upgrade some other appliance, like your car or your pacemaker, go for it, and report back soon.
Martin
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MGLloyd
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Joined: 31 Oct 2002
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Location: Mill Creek, Washington, USA
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Posted Fri Jan 23, 2004, 9:52pm
Subject: Re: Which Heat Gun?
 

Snap Said:

Stirring constantly is the best way to ensure an even roast (that, and allowing enough time before 1st c.) .  Using the heatgun to agitate beans is not.  At low CFM, it's necessary to get the gun nozzle right into or on top of the beans if you want a stirring effect.  Martin

Posted January 23, 2004 link

I wonder if 'stirring' vs. 'agitated' is merely a matter of semantics.  Certainly when I am moving beans in the bowl by stirring with a utensil vs. blowing with the heatgun, the beans seem to be tumbling and rotating regardless of method.  When using the heatgun to move the beans, they are not merely skidding about on a flat surface, but are rolling hither and yon as well.  I also agree that putting the muzzle too close at high heat can lead to scorching and incomplete roasting.  

I am beginning to think that the issue of stirring with aircurrents only may be very, very specific to the actual bean type (density and shape), the size/shape of the roasting vessel, the CFM put out by the heatgun and how close the muzzle is to the surface of the bean mass.  As such, it may be difficult to make generalizations.  I have noticed myself that the degree of supplemental stirring that I need with a utensil can vary depending on what bean I am roasting and which dogbowl I am using.  The CFM of the heatgun and the distance of the muzzle are constants.

As always, your mileage may vary but I would encourage people to err on the side of stirring with a utensil to ensure an even roast.

 
Regards,

Michael Lloyd
Mill Creek, Washington  USA
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jliedeka
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jliedeka
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Posted Fri Jan 23, 2004, 10:52pm
Subject: Re: Which Heat Gun?
 

Michael,

I was thinking about the evenness issue today.  I roasted a pound of Huehue using my usual kamikaze setup.  The Huehue is a small dense bean so I expected a fairly long roast to full city.  Plus it was barely 20 degrees here today.

Anyway, I tried keeping the beans in a nice layer and pushing heat in with minimal stirring.  That didn't work out.  By the time I noticed the top beans were tan, they were really tan with deep green underneath.  This was still way before 1st crack so I had plenty of time to even things out.  But I do think stirring constantly and slowly is important.  And moving the heat around.  Beans make terrible conductors.  I also think the small size of the bean contributed to a lack of airflow through the mass.

    Jim

PS: I am getting the urge to try a different roasting chamber.  I think my bowl is a hair too big.  I may be coming fully over to the dog bowl side soon.

 
Cafe todo el dia, tequila toda la noche
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computerDr
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Joined: 1 Jan 2004
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Posted Sat Jan 24, 2004, 8:04am
Subject: Re: Which Heat Gun?
 

Jim,
   I too roasted on friday when it was 20's in Chicago.

   It seems to me that under freezing it seems to get much more difficult.  I thought that was strange, but all of the roasting methods seem to stall out
when the temperature goes down.

    The raising the temperature of the beans by another 10 degrees or so seems to be a minor issue (going from 20 degrees to 500 rather than from 30).  The problem seems to be the loss of heat from the vessel (and from the top).

     What do you think about putting the nozzle into the beans so that it is more
even and more heat goes to the beans?

Jon
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RoboCoffee
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Posted Sat Jan 24, 2004, 10:03am
Subject: Re: Which Heat Gun?
 

Let's apply some more thermodynamics to the heat loss through the bowl issue. First, smaller bowl, smaller losses (actually, you want to minimize your surface/volume ratio).

Next, consider the thermal conducitivity of your bowl. Here, I may be a heretic - maybe metal bowls are bad. Metals have high thermal conductivity, which is good for heating from below but not from above. I doubt if anyone could roast coffee even in Tahitii in a thick copper pot using a heat gun.

So, we need insulators to conserve heat. How about wood? Maybe not. Glass is better than steel. Some ceramic bowl might be best.  You can find a nice table that can help you search through the kitchen here.
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computerDr
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Joined: 1 Jan 2004
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Espresso: Mini Grimac
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Posted Sat Jan 24, 2004, 11:05am
Subject: Re: Which Heat Gun?
 

Robo,
    Interesting table.  There is another problem with materials and that of course is the resistantce to heat---that is, wood catches fire, rubber will melt.  For example, pyrex is not recommended for stove top cooking.

    It was interesting to see that common building materials have low conductivity
(wood, brick).  I recently read a history of Gengis Khan, who lived in a really cold climate.  Their tents were made of felt, one of the smallest numbers on the chart.

    A vessel of clay (Jim suggested it to provide insulation) for directly holding
the beans might be best.

Jon
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