[Homeroast] heat gun method
wsmailmagnet at gmail.com
Thu Nov 11 14:30:45 CST 2010
At about the same point at which you are, I decided to buy a non-contact
infrared thermometer. Most are good to 1000F, and I have found mine to be
accurate in any roasting method where you can see (shoot at) the roasting
beans. It has also been useful for home projects where I needed to know the
temperature of a surface.
I addressed the air-vs-bean temperature issue by putting the probe in the
center of the bean mass (using SM's digital thermometer, in a homemade air
roaster, using a HG). This way, the hot air hitting the probe has been
through half the beans, the beans are contacting the probe, and the airflow
over the probe is "average". I compared readings from my non-contact
thermometer with the probed thermometer, and found that the tempeatures were
consistent enough for me to rely on the probe.
In the set-up you describe, the thermometer could be reading a higher or
lower temperature than "true" bean temperature. If the thermometer is hit
by the hot air before the beans, it will read higher than the beans. If the
probe is out of the airflow, and is heated by radiant heat from the beans
nearby, then the temperature will be lower than the beans. If the beans are
not adequately agitated, the temperature of the beans themselves will vary
(you indicated some variance in roasted bean color).
On Tue, Nov 9, 2010 at 11:11 PM, <msmb at suddenlink.net> wrote:
> Now that my I-roast has died I have been practicing with a heat gun method.
> Before I put any money into this I wanted to just try it out with whatever
> I had around the house. So I am using a 1500 watt Chicago tools heat gun
> with two speeds (a very inexpensive tool), a digital thermometer that goes
> up to 400F and a BBQ popcorn popper (a basket with small holes that you
> would put over a fire until the corn pops). I just tried 100g of beans.
> I pushed my digital thermometer through the basket so that the face of iT
> was just outside of it and the probe cut through the center and stuck into
> the other end of the basket. I then followed a procedure that attempted to
> approximate my I-roast profile. I started on slow speed and got the beans
> up to around 250 (with variations between around 220 degrees and 268
> degrees; it is a bit tough to keep the temperature steady; perhaps with
> greater experience this will improve). After 5 minutes I moved to an
> intermediate heat; with the heat gun on high I got the temperature to
> between around 330 and around 370. I kept this for around 3 minutes. Then
> I put the heat gone right up to the basket and my thermometer ultimately
> went to its limits and It would go between around 388 degrees and its cut
> off point; I just kept the heat as high as I could until second crack (my
> thermometer feel out but I assume that I was heating to the maximum; the
> beans did not cook very quickly or turn oily. Afterward I used a powerful
> little fan to cool for 2 minutes and then threw everything into a cast iron
> pan and put it in the freezer. The color looks pretty good; city to full
> city with some variation in the color of the beans though I have had many
> I-roasts that looked similar. But the total roast process took 17 minutes,
> compared to my 8 or 9 minute roasts with the I-roast.
> Here are a couple of questions. Since the heat will fluctuate up and down
> 40 degrees, will you end up baking the roast (I thought that temperature
> must remain stable or continually rise in roast)? Also, my digital
> thermometer is not measuring the temperature of the bean but of the heat
> hitting the probe. The I-roast also measured ambient temperature but that
> was enclosed in the glass receptacle for the beans and covered with a lid
> while mine are exposed to the open air all the time. I would compare mine
> to a mesh BB roasting basket; the difference is that while you can close
> the lid of the BBQ to increase the heat I can put the gun right up to the
> basket to increase the heat. Should I expect that the heat of the beans is
> greater or less than the ambient tem[temperature measure by my thermometer?
> Does 17 minutes seem like too long for this kind of roasting method with
> 100 grams (I expect that it will get faster as I increase the amount of
> beans, no?).
> Any feedback and suggestions would be appreciated. Thanks.
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