B-ROR shows a flick but I-ROR doesn't (and other questions)

my recipe is as follows:

  1. Preheat @ 428
  2. Initial setting of P7-F2-D9
  3. Drop from P7-P6 @ 350
  4. Drop from P6-P5 @ 370
  5. Drop from P5-P4 @ 390
  6. Drop from P4-P2 @ 400
  7. End Roast @ 405

Hey folks - this was my first roast ever! I’ve attached my curve and my recipe for reference. Not knowing anything about how this bean wants to be roasted, I went into the roast with the a pretty generic set of goals. I’ll share my goals and results here:

Target Weight Loss: 12% | Actual Weight Loss: 13.5%
Target DT: 1:30 | Actual DT: 1:22
Target DT %: 20% | Actual DT %: 14%
Target Roast Time: 9:00 | Actual Roast Time: 9:32
Target End Temp: 400 | Actual End Temp: 405
Color: Don’t own a color meter yet!



Around minute 7 , you can see a pretty significant flick on the B-ROR, but it doesn’t seem to flick on the I-ROR (although there is some considerable variability).

Would you drop the power a little earlier on to avoid that flick? Or should I ignore it because it doesn’t show up in the I-ROR?

2. Roast was too dark

The main problem with this roast is that it is too dark. Actual weight loss is proof of that. The reason I didn’t drop earlier was that I was trying to hit my goal of 1:30 DT with a DT% of 20%, and I didn’t even come close to hitting that goal. I held on for as long as I could, but still ended up too dark with a 14% DT% and a DT of 1:20.

3. Time vs Temp for recipes

Random question - do you favor time-based recipes over temp-based? From what I read, temp-based recipes are better because they are not affected by ambient temperatures, but Roos’ sample roasting recipe is time-based. Would you recommend I switch to a time-based recipe?

Potential Adjustments:

  1. Drop from P6 to P5 at 360 instead of 370, in order to better anticipate the flick.
  2. Increase P at drop to 8 instead of 7. The goal here would be to accelerate the drying stage of the roast, which would result an overall shorter roast, which would boost the DT%.
  3. End Roast at 400 instead of 405

Any advice or thoughts would be appreciated.

While I’m new to the Bullet, I have been home roasting for ~20 years. FWIW, I don’t think I have ever seen less than a 13% weight loss, it’s much more typically 14-15%, even at a city roast.

Before getting into the finer details, I have a few broader questions.

What’s your roasting experience? Why do you think your roast is too dark at a 405 degree drop temperature? Was first crack even complete yet?

This was the first roast I’ve ever done :slight_smile:

My statement that the beans were too dark at a 405 drop temperature was purely by observing the color compared to a couple of similar light roasted coffees I currently have.

Also, I came across a post on home-barista where a member writes,

“I drop light roasts around 385-390F (370 1C), which correlates to around 16% [DT%].”

1st crack was definitely over by 405. I try to mark first crack at the crescendo and I think in this case I was a little late on marking it because it was my first roast and I was nervous.

Regarding weight loss, see this Hoos article, where he writes,

11 - 13 % Weight Loss: This is, almost without exception, light roast territory. Generally, unless the coffee is quite wet, as you move above 13% you end up with what I would consider a light-medium or medium roast.

Interesting. I don’t know where it’s come from to drop a roast before or during first crack. That’s WAY too light IMO, terrible tasting. 385-390 cannot possibly be through first crack unless the instrumentation is significantly off.

I have never had first crack end by 405. Maybe by 410, usually more like 420.

More later…

Keep in mind every thermocouple is going to respond differently, so comparing temperatures across roasters is not easy. IBTS is much better. This might be helpful:

I get the bean-only “flick” as well. I think it’s superheated steam affecting the thermocouple but not the IBTS. I would ignore it.

I prefer temperature-based recipes. As you say, it’s going to adjust for conditions better.

What kinds of beans are you roasting? I take it you’re going for a light filter roast?

Thanks so much for linking to that spreadsheet - it’s super useful. Makes me feel better about not hitting the same temperatures mentioned in the other forums.

Agree that the bean flick could be steam - I would imagine that pattern could easily occur at small batch sizes (400 grams in this case).

I’m roasting a Costa Rican machine washed Caturra + Catuaí blend from Sweet Maria’s - it should be a good candidate for a light roast.

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