I think the main thing to take away from this is that the occurrence is to be expected… IBTS & BT move toward one another as 1C begins and as the crack progresses they nearly coincide. Whether IBTS descends toward BT or BT appears to climb toward IBTS, the difference between the two readings diminishes rapidly to the end of 1C then at a slower rate after that point. If you take the roast past 1C the 2 curves will get even closer. In trying to stretch the roast as I approach 2C I’ve managed to stall IBTS while BT still continues to rise slowly. I kinda paniced when I saw that but the result was ok.
All this depends to a great extent on batch size as BT readings are higher relative to IBTS with larger batches. Or said another way, I think (YMMV!) IBTS readings are largely independent of batch size while BT readings are not.
Depending on the range of wavelengths that the IBTS is sensitive to, the signal will be reduced by water vapor. Does anyone know over what part of the IR spectrum the IBTS is sensitive?
BTW, coffee_5624a418348c, what you have is not a flick and crash (Rao describes it coming in that order). ROR curves are noisy, and your curve is a good example.
I follow a tip from BradM, who suggested getting to an ROR of 10 at FC. That would mean reducing heat earlier, maybe adjusting power to P5 at 5 minutes or so.
Unrelated question but how are you getting such smooth I-ROR lines???
Mine fluctuate all over the place at the start and then smooth out a bit but yours looks almost drawn with a ruler! Is it just I changed fan speed more where it looks like yours is more power controlled? The large fluctuations at the start usually mean I just ignore the I-ROR graph for the most part.
Hey @gregv50d it looks like your blue IBTS temperature curve has some fluctuations in it at times of about 0:50, 1:45, 2:30, … which would definitely lead to bigger fluctuations in the corresponding RoR. I’ve seen those IBTS temperature fluctuations a few random times and tried cleaning the sensor. Didn’t see any obvious grime on it though. One other time I got a huge drop-out in IBTS temperature (20C drop over 15 seconds) which may have been a flake of the very large, chaffy Brazilian natural bean getting stuck on the sensor?
I do like to use as low a fan setting as possible (just enough to pass the “lighter test” and remove most of the chaff), and modify power to control RoR. Not everyone agrees with this but for me it’s delivered a better cup.
Thanks @bradm. I’ll try on my next roasts to adjust the power more and see if I can get it more stable. Was shocked to see consistent your ROR lines were. I’ve all but ignored my I-ROR line because of the huge swings.
I have 10 ish roasts on the new bullet but will pull and clean the sensor this week before I try again. Maybe the seasoning roasts have it extra dirty.
Thanks again for the feedback. At least the roast tasted good but would like the graphs to reflect the same if possible.
And should add - open to any other feedback on that roast as well. Still really new with the bullet so I’m open to criticism.
@jacob thanks for the reply. The batch size for that one was 500g. Suspect that’s the issue? Let me know if there is anything I can help diagnose. This all on stable but can move to the beta if that’s stable enough to test and rerun that batch.
Yep that has become my baseline profile for medium-light roasts. It works really well on the pink bourbon - sweet, fruity, good balanced cup. You can vary the duration of each power segment and the time when you bump the fan up to F3 as needed to match the IBTS temperature curve for similar beans.
That roast comes fairly close to the magic formula of 45-35-20 time intervals and 30-20-10 average BT-RoR intervals (in F/min). The profile needs a little fine tuning to hit the formula for each new bean.
When I Updated to Roast time 3.1 (where I-ROR curve was available) all previous roast showed smooth I-ROR but current roasts aren’t smooth as the previous.
Interestingly, I too have wild swings in the IBTS RoR curves. They are definitely somewhat dependent on batch size, but I suspect something more is going on. For example, the variability is decidedly NOT random. It is almost periodic, with a period of about 20 sec. But I also notice that OLDER roasts are incredibly smooth. The first one below is a 220g roast from last week, and the second one is from February, also 220g.
That’s really interesting… I guess it is a really new feature and maybe the bugs are getting worked out. I don’t find very useful or trustworthy in it’s current form but going to keep it on and hope I can see consistent results.
Or @jacob anything we can do to either help test or settings which would smooth out the results (but not lose reality at least)?
From what I recently tried, with larger batch sizes BT comes closer and closer to IBTS as batch size increases, i.e. IBTS seems to be independent of batch size but BT is not… so BT is the variable.
Later in the roast, lowering drum speed will increase B-RoR. It works in reverse as well- raising drum speed will lower B-RoR. I haven’t seen the correlation as distinctly in the front of the roast… it’s either vague or not correlated.
I haven’t been able to establish a clear association between I-RoR and drum speed. B-RoR vs. drum speed has been sufficient for my purposes but I really would like to add I-RoR to the toolbox. If you work it out I hope you can share it here!
