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Date: 01 May 2007 17:32:38
From: Jim
Subject: Temperature control with hot air roasting
I have a hot air roaster that I rewired for heat with air, or air only.

What should I be aiming for as far as roasting times? For example, how
long to first crack, how much time between first and second crack, etc.

Somehow, I got the impression that fairly rapid roasting to first crack,
then holding the temperature for a while and delaying second crack was
the way to go. Then cooling as rapid as possible. Am I off track?

I use bean quantity, angle of the popper, and the heat on/off switch to
regulate. I've got a pretty good feel for how to do it (just based on
experience of times to first and second crack), now I need suggestions
on what to aim for. I'm roasting for espresso, I don't like a burnt
taste, and I'm using Sweet Marias monkey blend.




 
Date: 02 May 2007 01:24:29
From: Randall Nortman
Subject: Re: Temperature control with hot air roasting
On 2007-05-02, Jim <askme@beforeyousend.com > wrote:
> I have a hot air roaster that I rewired for heat with air, or air only.
>
> What should I be aiming for as far as roasting times? For example, how
> long to first crack, how much time between first and second crack, etc.
>
> Somehow, I got the impression that fairly rapid roasting to first crack,
> then holding the temperature for a while and delaying second crack was
> the way to go. Then cooling as rapid as possible. Am I off track?
>
> I use bean quantity, angle of the popper, and the heat on/off switch to
> regulate. I've got a pretty good feel for how to do it (just based on
> experience of times to first and second crack), now I need suggestions
> on what to aim for. I'm roasting for espresso, I don't like a burnt
> taste, and I'm using Sweet Marias monkey blend.

I am only about 3 months into my home roasting career, so I am by no
means an expert. The first thing I've learned about hot air roasting
is to not try to emulate drum roasts. Ignore those 18 minute roast
curves -- if you try that in an air popper, you'll bake the beans.

If you like really bright/acidy coffee that's light on body, by all
means go for the 6-minute roast. But you're roasting for espresso, so
you probably want more balance. I have tried the "rush to 1C, drag
out the period between 1C and 2C" approach, and I don't particularly
like the results. Yes, acidity is muted, but so is everything else.

My current profile, always under development, but the best I've found
so far, is this:

(All temperatures from a probe inserted into the middle of the moving
bean mass, not touching bottom or sides of roast chamber)

1. Drying phase: bring the beans to 200F quickly, then bring them
very slowly to 300F. I aim to hit 300F at about 3-4 minutes.

2. Sprint to 1C: go full bore until you hit 415F or hear the first
hint of 1C, whichever comes first (and it will probably be the
cracks)

3. Back off and maintain temperature of around 430F until first crack
is done. Do your very best never to let the bean temperature actually
fall; keep it steady or slowly rising.

4. As soon as you are clear of 1C (usually around 8 minutes for me),
ramp the temperature steadily, without letting it race out of control,
until you reach your desired roast. Total time for me is usually 8-12
minutes, and I try to be in the middle of that range rather than at
the extremes. I rarely roast much into 2C if at all. You say you
don't like burnt tastes, so I'd advise you to stop the roast as soon
as you get the first hints of 2C, or even earlier, but you'll want to
be well out of 1C territory. Definitely don't let it invade French
territory. Nothing good ever comes of invading France, tempting as it
may seem.

I should also say that I got a 1500W light dimmer switch on eBay for
about $30 shipped, and this makes it much easier to keep the
temperature on a steady march than flipping a switch on and off
manually. (Only the heater is on the dimmer in my setup; the fan runs
full bore all the time.) A variac is an even better option,
especially if you have problems with voltage drops or stalled roasts,
but those are more expensive.

--
Randall


  
Date: 02 May 2007 09:29:58
From: Randy G.
Subject: Re: Temperature control with hot air roasting
Randall Nortman <usenet8189@wonderclown.com > wrote:

>On 2007-05-02, Jim <askme@beforeyousend.com> wrote:
>> I have a hot air roaster that I rewired for heat with air, or air only.
>>
>> What should I be aiming for as far as roasting times? For example, how
>> long to first crack, how much time between first and second crack, etc.
>>
>> Somehow, I got the impression that fairly rapid roasting to first crack,
>> then holding the temperature for a while and delaying second crack was
>> the way to go. Then cooling as rapid as possible. Am I off track?
>>
>> I use bean quantity, angle of the popper, and the heat on/off switch to
>> regulate. I've got a pretty good feel for how to do it (just based on
>> experience of times to first and second crack), now I need suggestions
>> on what to aim for. I'm roasting for espresso, I don't like a burnt
>> taste, and I'm using Sweet Marias monkey blend.

>I am only about 3 months into my home roasting career, so I am by no
>means an expert. The first thing I've learned about hot air roasting
>is to not try to emulate drum roasts. Ignore those 18 minute roast
>curves -- if you try that in an air popper, you'll bake the beans.
>
I would not follow that as a rule. Yes, 18 minutes is a long time- too
long really, but the typical uncontrolled air roaster curve is too
fast. As an example, the Hearthware Gourmet and Precision both roasted
very fast (total time of around 6 to 8 minutes I think) and the roasts
were always overly bright (at least for espresso). The iRaost2 which
works much the same way but allows for programming to slow the roast
created a much more balanced flavor with a roast of about 11 to 14
minutes.

Of course there are factors to be considered like personal tastes,
method of brewing and what beans are being roasted. But thermal energy
is thermal energy, and the device used to roast is (generally) less
important than how the roast level is achieved. Second crack can be
achieved in virtually an infinite numbers of ways. Personally, I still
like a slower ramp to around 300 or so and letting the beans lose
their moisture slowly then ramp up to first crack at ABOUT the nine or
ten minute mark, then throttle down the heat allowing about a one to
two minute pause before second starts.


>If you like really bright/acidy coffee that's light on body, by all
>means go for the 6-minute roast.
>
I agree. Personally I find that sort of roast unpalatable.

> But you're roasting for espresso, so
>you probably want more balance. I have tried the "rush to 1C, drag
>out the period between 1C and 2C" approach, and I don't particularly
>like the results. Yes, acidity is muted, but so is everything else.
>
I do not like the rush to 1st. it does not allow the inner areas of
the beans to come up to temp and lose their moisture and the outer
bean is well ahead in the race.


Randy
"roasted 4 batches yesterday-
my brother will be very happy later today!"
G.
http://www.EspressoMyEspresso.com




  
Date: 02 May 2007 07:27:10
From: Ian Smith
Subject: Re: Temperature control with hot air roasting
On Wed, 02 May, Randall Nortman <usenet8189@wonderclown.com > wrote:
>
> (All temperatures from a probe inserted into the middle of the moving
> bean mass, not touching bottom or sides of roast chamber)
>
> 1. Drying phase: bring the beans to 200F quickly, then bring them
> very slowly to 300F. I aim to hit 300F at about 3-4 minutes.
>
> 2. Sprint to 1C: go full bore until you hit 415F or hear the first
> hint of 1C, whichever comes first (and it will probably be the
> cracks)
>
> 3. Back off and maintain temperature of around 430F until first crack
> is done. Do your very best never to let the bean temperature actually
> fall; keep it steady or slowly rising.
>
> 4. As soon as you are clear of 1C (usually around 8 minutes for me),
> ramp the temperature steadily, without letting it race out of control,
> until you reach your desired roast. Total time for me is usually 8-12
> minutes, and I try to be in the middle of that range rather than at
> the extremes.


Which is interestingly close to what I do. There's a graph at
http://www.astounding.org.uk/ian/roaster/realroast.png, but compared
with the above description:

1: I get to 150C (302F) at 2 minutes, so rather faster. However, I
limit heat input to this stage to about 70% of full power, so the
beans don't get hit by extreme temperature variation.

2: I go steadily to 215C (419F) at 6 minutes. This is generally first
crack going nicely. First crack is over around 7 or 8 minutes.

3: I ramp slowly to somewhere between 230 and 250C (446F-482F) and
hold to get the desired roast at about 12 minutes.

regards, Ian SMith
--


  
Date: 02 May 2007 04:03:29
From: Steve
Subject: Re: Temperature control with hot air roasting
On Wed, 02 May 2007 01:24:29 GMT, Randall Nortman
<usenet8189@wonderclown.com > wrote:

>I have tried the "rush to 1C, drag
>out the period between 1C and 2C" approach, and I don't particularly
>like the results. Yes, acidity is muted, but so is everything else.

Very true in some coffees and blends.
In others...

That's the art, and fun of it.