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Understanding the Curve


exer31337 wrote:

There was a post of a formula that I can't find. The CoffeeMind approach of ET control sounds much easier to experiment with vs roasting based on the outcome of the ET (ror). Someone posted a formula to create the desired roast profile based on ET, I was wondering if someone had a link to it, or a better way to plan the roast curve based on ET...
Anyways trying to find a way to plan my roast profile and Dev time with specific ET targets.


Guilty, I admit ! Grin
Probably you mean this thread: https://homeroast...post_62977,
...and the followup of @allenb: https://homeroast...post_73942
...the formula you asked is in post #12 of Allen thread, linked above.

There is a problem with pro lessons, almost all are based on commercial drum roasters, whose thermodynamics are significantly different from the home machines we are used. Some Rao commandments also...
Try applying drum roasting principles on a FB and you "crack" with style... and viceversa.

Also, even size matters, I didn't seen so far a well done small drum roaster, under 600 grams, that "quacks" as a drum roaster.
All the 250-500 machines sold so far just tries to mimic drum roasting with little success, imo. Statement based on real pro owners trying to use them as samplers.

In this context, the last paragraph from JS quote, in the thread mentioned above has even more weight:


This ET part is basic roasting chemistry, and the same for all roasters and coffees. But the heat inputs required moment by moment to achieve this ET curve is based on the roaster's thermal characteristics, and is different for every roaster design. "

For a hot air machine, your life is the easiest possible... you don't even need to follow/measure ET, because it is very strict and close related to power level. Actually this is the way how I roast in the last years, using a power profile, instead temperature, and monitoring BT just for the record, not for controlling in real time the power in order to force the roast following something.
Seems to be the strategy adopted more and more by Ikawa users too, after years trying to understand that their precious machine is not magic, and don't guess their thoughts.
It's curious and sad too see that the main tool used for computer roasting this days, you know its name Grin don't embrace and offer support for roasting based directly on power profile, and stagnates on temperature only.

This is the part that I dislike personally the most for a drum roaster: you can't relate directly the power level to ET... the thermal inertia of machine make this process too guessing.
And also don't forget there was introduced a second factor that complicates things even much: the airflow...

End of rant Grin


renatoa wrote:
It's curious and sad too see that the main tool used for computer roasting this days, you know its name Grin don't embrace and offer support for roasting based directly on power profile

For the past 18 months I have been roasting strictly with power profiles using Artisan. Although it isn't as easy, or as convenient as using the integrated profile designer tool to create a BT curve for PID use. By using multiple time-based alarms one can trigger any power level at any moment during a roast. This creates the resultant BT curve smoothly and naturally. However, it does take good knowledge of the thermal characteristics of the roaster in use, how it will respond to heat inputs (lag, heat loss, etc.), but it does work wonderfully.

That being said, it certainly would be nice to have an integrated tool for creating a power curve easier....
Or simply extract a power profile from and existing roast, and follow it.
Exactly, by lacking support I meant make it easy !
Finally... we have science ! https://www.natur...24-57256-y
What a great find! Thanks for sharing.
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