I did my first roast today after three seasoning roasts and I have a few questions. I did 450 grams of a washed Ethiopian. I hit first crack at around 365-370 degrees Fahrenheit on the IBTS which seems really low to be hitting first crack so I was very surprised. I was shooting for a full medium roast so I dropped the beans about 15-30 seconds after first crack ended. When the beans got in the cooler I noticed there were a bunch of random burnt beans in the cooler as you can see in the photo below. I picked all of them out. Any idea what could of caused that? I was very confused to find them throughout the finished beans. Thanks for any input!
As a guess I would say the IBTS needs cleaning. When IBTS and the Temp Probe swap position before the end of your roast it’s almost a certainty the IBTS needs attention. My experience has been the IBTS is always at a higher temp than the probe at drop.
SO your next question is probably ‘why did it get dirty in 4 roast?’ I’ll guess again and this time it’s that there is some residue from mfg or maybe from the dark-roast nature of the seasoning roasts. The first cleaning seems to take several passes to make a difference so repeat the cleaning a few times (cotton swabs & alcohol). Be sure to start by cleaning the opening in the rubber view port before going after the lens (clear glass surface of the IR sensor).
The remaining possibility is the least desirable and that’s that the calibration of the IBTS is in error. So start with cleaning the IBTS. If you still have the same issue then your next stop is to talk to your Bullet supplier or Aillio Support. The latter is in Taiwan so allow for differences in Time Zones.
Keep in mind that the IBTS is the source of temp data for Preheat. If the IBTS is reading low (which is my guess is happening) the actual temp of the drum is higher than what you selected for the Preheat setting. The temp probe is used during Preheat but only to verify the temperature is stable at the end of the process (no more than X° in 1 minute; sorry- I forget the exact number).
A suggestion for identifying 1Cs (1st Crack Start as opposed to the ambiguity of FC which is also used to identify Full City): there’s a lot bean noise inside the drum making it hard for some to distinguish the sound. So don’t try to mark the event using the first sound you hear. Instead wait for say the 3rd or 4th crack sound. Doesn’t fix the issue but it will help with consistency.