Allio Bullet - Advice on Brazil roast curve?

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
Iowa_Boy

#1: Post by Iowa_Boy »

Just when I thought I was figuring out my Allio Bullet, I am struggling with a Klatch Brazil Diamond Reserve.
I am doing a 225 gram batch size, with 392 charge temperature. That seems to be working really well for most beans.
For some reason, once I hit first crack on this bean, the ITBS bean temp seems to be going up really slowly, almost stalling.
See roast curve below. I was trying to hit a temp of 413 before dropping the beans, but eventually gave up when my DTR was 27% as I assumed they were baking at this point.
Any advice what I am doing wrong? Or could it be something with the greens?
I assume my ROR is too low once I hit FC, but it seems like it still should be high enough that it should drive the roast forward.
My previous Brazil roast had similar issues after FC, even though the ROR was higher.
Roast Vision was a 20 for this roast.

In contrast, my second roast of the day, Captain's Ethiopia Sidama Bombe, went right according to plan.
Dropped at goal temp of 413, Roast Vision was an 18. I was trying to roast just a bit darker than my previous roast, which was a 411/Roast Vision 19.
Can't wait to try the Ethiopian.
Appreciate any advice!

Both roast curves are below:


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GC7
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#2: Post by GC7 »

... duplicate response .. please remove.

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GC7
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#3: Post by GC7 »

I have never roasted less than 325 gm on the Bullet. Thanks to guidance from BradM for most beans this mass works fine. I am presently using 1 pound charge mass for most roasts.

The common belief is that using charge masses less than about 350 gm leads to somewhat unreliable bean temperature measurements. The thermocouple may not be in contact with the beans enough with the drum size of the Bullet.

Your ROR graph looks nice but it shows only the BT probe measurements and not the IBTS. The bean temperature measurements show reasonable/good temperature development following first crack. What is stalled is the IBTS curve which for your charge mass (225 gm) should better reflect the roast dynamics. If you want to continue with the 225 gm roasts I might use IBTS ROR curves to guide you through maillard and post-crack development. That's where I would start.

Hope this helps.

Otaibimn

#4: Post by Otaibimn »

If you are getting a smokey taste in the cup, Drop drum speed to 7. Hell, just drop it anywhy and try. If you find you are getting better results, Start the drum at D6 and up it until you reach D9 at the start of FC.

D9 is so fast you will stick the beans to the drum walls and over roast the outer of the beans. Once you hit FC you can up it to D9.

Found the best size batch for consistent roasts is around 500g-600g. Probes are reading fine and you are getting good readings.

Power seems to be fine overall (Might start at P8 if you up the batch size).

I will also try to hit FC at 8:00+/- 10 seconds.

Iowa_Boy (original poster)

#5: Post by Iowa_Boy (original poster) »

GC7 wrote:I have never roasted less than 325 gm on the Bullet. Thanks to guidance from BradM for most beans this mass works fine. I am presently using 1 pound charge mass for most roasts.

The common belief is that using charge masses less than about 350 gm leads to somewhat unreliable bean temperature measurements. The thermocouple may not be in contact with the beans enough with the drum size of the Bullet.

Your ROR graph looks nice but it shows only the BT probe measurements and not the IBTS. The bean temperature measurements show reasonable/good temperature development following first crack. What is stalled is the IBTS curve which for your charge mass (225 gm) should better reflect the roast dynamics. If you want to continue with the 225 gm roasts I might use IBTS ROR curves to guide you through maillard and post-crack development. That's where I would start.

Hope this helps.
Thank you = that is very helpful!! I am embarrassed to admit that I didn't even realize I was looking at BT ROR curve rather than the ITBS ROR. I turned on the ITBS ROR, and the curves are below. A lot noisier, but clearly shows the ITBS ROR is bottoming out. Interesting that the BT and ITBS ROR more closely track each other on the second roast of the day (the Sidama Bombe).



Iowa_Boy (original poster)

#6: Post by Iowa_Boy (original poster) »

Otaibimn wrote:If you are getting a smokey taste in the cup, Drop drum speed to 7. Hell, just drop it anywhy and try. If you find you are getting better results, Start the drum at D6 and up it until you reach D9 at the start of FC.

D9 is so fast you will stick the beans to the drum walls and over roast the outer of the beans. Once you hit FC you can up it to D9.

Found the best size batch for consistent roasts is around 500g-600g. Probes are reading fine and you are getting good readings.

Power seems to be fine overall (Might start at P8 if you up the batch size).

I will also try to hit FC at 8:00+/- 10 seconds.
Interesting, I really haven't tried adjusting drum speed, as I wanted to limit the variables I was adjusting. Although I haven't appreciated smokey taste with previous roasts, it's easy enough to try a lower drum speed like D7 and see what it does.

Hmmm... Both times I have roasted the Brazil greens, it has been the first batch of the day. I wonder if I am not letting the drum preheat long enough. Generally I wait about 5 minutes after the drum reaches temperature, but it hasn't switched to charge automatically. Could that explain the BT/ITBS inconsistency in the first roast that gets more consistent for the second roast?

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GC7
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#7: Post by GC7 »

Iowa_Boy wrote:Thank you = that is very helpful!! I am embarrassed to admit that I didn't even realize I was looking at BT ROR curve rather than the ITBS ROR. I turned on the ITBS ROR, and the curves are below. A lot noisier, but clearly shows the ITBS ROR is bottoming out. Interesting that the BT and ITBS ROR more closely track each other on the second roast of the day (the Sidama Bombe).
Natural Ethiopians usually show better balance and coordination between BT and IBTS probes. Some other origins are just more difficult. Bombe roasts beautifully in the bullet. Here is a 340 gm roast that I am drinking now. For these beans I stick with my 340 gm profile since it always seems to cup so well. Others I find the control easier with a pound starting. Others prefer even higher charge masses for best control.

Your Brazil roast definitely crashed on the IBTS probe.


Iowa_Boy (original poster)

#8: Post by Iowa_Boy (original poster) » replying to GC7 »

Thank you again! I think I was not preheating long enough, which was why the BT/IBTS probes weren't better coordinated.
Today, I did what I should have done before, which is preheat until the Bullet said Charge, instead of loading beans much sooner.
Also changed the drum speed to D7.

The first roast today was the Bombe, but once it was preheated properly the roast went faster than I expected.
For Roast 2 which was a Yemen Mocca Kholani, I adjusted charge temp to 383, and lowered power to P6 to start. The curve for that looks pretty good and is the one below. May lowered the power a bit too quickly at the end, or maybe Fan 4 is just too high for this batch size. But overall happy with how it looks.
Roast vision is 19. Have never roasted this coffee before, so excited to try!


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mkane
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#9: Post by mkane »

Pre-heat is key with our unit. If we don't ET won't come close to 475°. The machine acts like a big heatsink. Either that or roast a small batch of coffee into 2C and then were off and running.

The faceplate on our unit is 1/4" thick.

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GC7
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#10: Post by GC7 »

mkane wrote:Pre-heat is key with our unit. If we don't ET won't come close to 475°.

The machine acts like a big heatsink.
This IMO as well! Notice the ~70* difference in bean probe temperature reading on charging between our roasts. Get the unit at a stable temperature. Some users wait a fixed time to charge but after the unit tells you to charge. You will need to then adjust power and fan settings over the course of the roast to get to your goals.