These experiments are pointing at a change in roasting techniques. This could bode well for the coffee business.

just did an Indonesia Gayo wine, extremely fermented and intense Winey taste, I am having much success with the Zero airflow method, followed by rapid convection. This coffee is extremely tricky to roast due to its high degree of fermentation, for extremely fermented beans, the trick seems to be as short as a roast time as possible, the longer roast times seems to accentuate the extreme fermentation notes more. However Indo beans are usually less dense and hitting them hard with high heat seems to cause over development on the outside, under development on the inside.



0 airflow, with a stopper on the air pipe to prevent steam from escaping, around the 4.30 min mark, slightly higher than normal airflow, followed by aggressive cuts to power, Scott Rao ROR style. Using this technique seems to help alot with the flicks and crashes with i usually get with this beans. Dry cupping wise, no hints of under development, color looks more medium, but the 14% weight lose seems low for such development.

Rytopa wrote:just did an Indonesia Gayo wine, extremely fermented and intense Winey taste,

The cup is all that matters, but I would try to tame that RoR spike. Maybe charge hotter/hotter DE ramp?

Beans tend to take on heat quickly once the free water dissipates and after DE. That much of a spike would be a shock. But again...taste is omnipotent. I'm just trying to stop the black helicopters from coming to take away you roasting credentials.

One thing I've noticed when trying this is that the roaster, and ambient air around it, gets significantly hotter. Be careful. Make sure there are no combustibles in, around and under the roaster.

All those burner BTUs are not going up the exhaust any more so they end up in the room with you.

The sudden spike in ROR is most probably the sudden release of energy with the airflow shock, my goal is to try shorten the total roast time, so i am literally sprinting towards 1fc at this point. The smooth ROR decline still applies, right after DE, any crashes or flicks will be detrimental to taste.

Yes, becareful with the heat build up, the way i see it is like a slingshot, during the DE phase there is alot energy stored in the drum, metal, steam, etc, overextending this DE phase however can lead to the undetached chaff charring with this method. The next phase is letting go the slightshot, and guiding the energy into the beans via convection.

I tried 2 more this morning. First, a Brazil taken to the edge of 2C. Opening the air to 50% caused a semi-flick. But I think the main issue was not enough early heat and throwing to make it up caused to much going into 1C: Agtrron: 46/52.



This roast went darker that I would have liked, but it's a Brazil for iced coffee. I'm drinking a cup now and it is sweet, pungently caramelized and not roasty.



For the 2nd I tried just keeping air at 25% for the entire roast.
I increased the initial heat setting from 50% to 67%.
This helped ramp to DE match my normal roast profile, but gas input was 40% more to get there.
Possible lesson: roasting on a machine designed to use lots of air might not be the best platform for conduction-based roasting.
Agtron 51/56.



I kept the 25% air setting untll RoR started to flick and I opening up a bit more. I shut off the flame well before, so not as much reserve heat available, which would have enhanced the flick.

This roast is my espresso blend and hit all my milestones. This should be a good flavor test, even though the air wasn't at 0.

I made a couple of Americanos this morning with my usual espresso roast and this lower airflow version.

Honestly, they were very similar. I got a bit more acidity from the usual roast and a bit more sweetness from the low-airflow. But I had to go back and forth a dozen times. It was so close, the difference could have been the Mythos II and Helor Stance Motor. I'll try again Wednesday after they have rested and use the same grinder.

My thinking is letting enough air into the system to divert the smoke from the room to the outside is enough to cause a convection reaction. I might just be using a more reasonable amount of air at 25% than the 75% I had been accustomed to. It will be very hard to roast at 0 without a respirator.

I've got to try this low air for entire roast experiment as well. Then one with more air than normal for entire roast. Unfortunately, I am going on a trip and won't be able to give it a go for another 10 days.

Al, do you have a fixed drum speed? I know, one thing at a time! But I feel drum speed is another variable that alters convection vs conduction.

My drum speed is fixed. I have a replacement motor and matching VFD to make it variable speed, but I haven't been motivated to install it. There is some programming of the VFD involved and my brain is feeling a bit maxed lately. I'm afraid if I try and stuff anything more in there, it might crash.

I could use it on my airflow as well.

The trick with trying to maximize conduction vs convection is finding the setting that is just enough to bleed off the smoke, yet not suck lots of hot air into the drum.

I just did this roast. I forgot to indicate my initial settings, but it was 25% throughout, until the end and 0 power until about 0:45, where the blue diamond is.



Of note is that the power settings were exactly the same as the background roast. The ET was less due to the lower airflow, but the BT rose the same. That tells me that some airflow is being wasted during dry, possibly doing more harm than good? Unless you believe that there are undesirables in the initial steam that should be exhausted out for better flavor.

And another thing I have noticed, managing RoR is much easier with less airflow.

It is likely that this air flow damper system has more to do with chaff removal, collection, and smoke removal than roasting performance. This system was likely added as a consequence of experience and closed drum initial development.

Non rotating perforated drum: http://www.youtube.com/watch?v=ctkli6NzUi8