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Variation in temperature read
Hi all,

Im a long time lurker, first time poster.

Got my Gene a couple of weeks ago and been trying to find some good profiles for my favorite beans.

Up till this point I have about ten roasts under my belt but only two of them have been successful.

I've used the suggested way to calculate BMT by Ciel-007

Tonight I've done three consecutive batches with some strange result. The first two of them I did with a Ethiopien Yirgacheffe that I never roasted in the Gene before and during today's roasting I never got to SC and therefore never could single in on a good temperature to reach the desired 4 min between FC and SC.

I decided to leave the Yirgacheffe for the time being and insted do a final roast with a blend I previously been successful with (50% kenia aa, 50% El Salvador Finka).

Doing the same routine with preheating, drying phase, ramp and ambient temperature I got totally different drum temperature then when I roasted the same beans a few days ago. The temperature rose faster and was about 10 Celsius or 18 F above the previous roast. How ever, all other signs of the roast were extremely alike that earlier roast. The tan stage and the light brown stage came almost exactly on the same time in both roast. Start and finish of FC came in a matter of seconds from each other. The end result looked very consistent with the city+ I did in the first roast.

Is there some explanation why the temperature reading in he drum could be so different?

Can it have to do with lack of cleaning. Except emptying chaff I have not yet cleaned it any other way.
One thing that strikes me immediately is the difference between a preheat from a cold start and the preheat in the third of a series of three roasts, if the machine was not allowed to cool in the interval. I do three 227gm roasts in a row and the interval between them is pretty brief. In each case, I preheat the container to 350 but that is just the air emerging. There is a great difference in the temperature of the whole pathway, and so the rate of temperature rise for the third roast is always faster for the third than the first roast. Could this be the reason?
Barrie (San Diego, CA)
"So much to learn, so little time."
Hottop 2K+., Artisan, Jura Capresso ENA 3 (i.e. espresso).
It could very well be that it's the back to back roasting that is to blame. I've tried to compensate for the build up of heat by running a full cooling circle in between roasts but it might not be enough.

The first roast I did when the temperature was significant lower was the second roast that evening, but it might be a difference between second and third batch of course.

Could it be that the gene shows stabile temperature if roasting two batches back to back but not three?

How's your other guys experience with back to back roasting? Something to avoid?
Steve Egge
Back to back roasting is great with the Gene.
I preheat to 300 ... just turn the machine on and get all my stuff ready, scales, external timers, cooling tray, etc and after 4 -5 minutes I start with my usual heating of the beans at 300F for 4 minutes or so ... then crank it up.

Lots of profiles out there to try. Haven't settled on one yet. Also fairly new to the Gene.

I just bought some cheap beans fro SM's (Panama "Dry Process Experiment Gone Awry" ) and plan to heat on a profile ... stop the roast and open up the drum and get first an infrared temp of the beans and second a thermometer probe of them.

I know it won't be totally accurate but really want to know where the beans are when I pause at a temp ... will be fun to experiment with them.

Steve Egge
Santoker Rev 500, Baratza Vario-W, HG-One, Bunn Trifecta MB, AeroPress, Londinium I
John Despres
Yes, you're experiencing back to back roasting effects.

You have a couple choices - allow your roaster to completely cool between roasts. I think this may be about 45 to 60 minutes and not very practical. Your second choice is to seriously preheat the roaster - not just the drum, but get the entire machine: the drum, the cover, the casings and everything else as hot as the machine is at the end of two or three roasts.

The trick is to keep your own notes and track your own successes and failures in order to improve your roasts.

Have fun!

Respect the bean.
John Despres
Fresh Roast 8, Gene Cafe, JYTT 1k, Quest M3, Mazzer Mini, Technivorm, various size presses and many more brewers.
Thanks for the answers and advice!

It do seems like its just the back to back roasting.

I don't know if I would have dared to by the Gene not knowing about this forum. The experience with the Gene in Sweden where I live is pretty scarce. No retailers and a bit of a problem with support over all.

I'm pretty new in the speciality coffee world. Roasting was the thing that really got me going and the Gene so far is really great. After a couple of pounds of "calibration batches" I now started to get really decent result. The room for improvement is vast so it will be great to see how the result will develop.

Mattias Lundström
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