Replies to This Discussion

Permalink Reply by Owen O'Neill on January 29, 2008 at 5:41am

Just curious... do you track or plot the bean temp increase to achieve a certain curve of temperature to time relationship and if so do you adjust flame or airflow aty any poitn to increase or decrease any temperature plateau?

Permalink Reply by Jason Casale on January 29, 2008 at 7:31pm

Owen Our air flow remains open all the time.
the agrton is set up for the most part to roast an optimal roast.
I timed it today. 1st crack is around 12 minutes finish between 15 to 16 seconds.
The agtron turns the burner on and off several times during the roast at varying lenths full on or full off.
We use an air density calculation to get our optimal charge weight. today it was 20.25 pounds.
There is a transition point we figure out by getting the bean density for instance todays bean density for yirgacheffe was set to 277 degrees elsalvador was 281 degrees This is the point where the coffee starts to actually roast before this temp the coffee is just getting warm in the green state elminating moisture and polyphenols At this transition point you see the coffee converting from green to light yellow and the roast continues from there. Our drop temps are about 450 460. turn around on the bean probe is 170 or when we reach thermal equal Librium Our first crack starts between 370 and 380. Finish the roast at rolling second 430 The beans are removed and are still dry. The agrton verifies roast level todays roast where between agtron 40 and 43 whole bean ground was 50 53 ten point spread between ground and whole bean is optimal. However to get accurate results you must calibrate your agtron every time you use it. In short the agtron once the transition point is entered and you drop your charge weight at 450 takes the coffee thru the correct profile we have to babysit the roaster and verify 1st crack happens at the correct time and temp and eject the coffee at 430 bean temp.
Hope that helps.

Permalink Reply by Instaurator on February 1, 2008 at 12:06pm

Hi Jason I've roasted with and without the Agtron control system. It is very effective in that it treats each coffee roast as a unique entity; there is no one time/temperature curve for different roasts because the infinite number of factors that go into affecting the roast development are never the same for any two roasts. By the same token I have roasted without it and achieved good results too. Many so-called artisan roasters don't seem to like it because it takes some of their sense of control away and/or they don't quite understand it fully, but the reality is it actually allows a more coffee sympathetic roast to develop rather than a human-centric roast. By this I mean as humans we can only control a few factors in the roasting equation at any one time whereas the Agtron control system allows for a much greater number of variables and calculates in a kinetic responsive way and theoretically adjusts the roast hundreds of times during the course of one roast. One difficulty I had though was varying the starting temperature but other than that it is a very interesting approach to good coffee roasting

Permalink Reply by Jason Casale on February 4, 2008 at 8:25pm

Wow Instaurator,
I am honored sir you replied to my roasting post.
I listened to you on the coffee geek podcast.
I have mad respect for you sir.
Cool agtron is cool I like it.
It is easy to use with the correct calculations. We are roasting on a samiac 10 kilo
Before I started a village coffee I roasted on a 3 kilo manual roaster and good results but it was difficult to get consistent reproducible results. After about 2 years roasting then cupping the results I got to be really good with it but my roasting business closed and I had to sell of my equipment. Ohh well. Anyway mad props to you Instaurator in house. How cool is that.