Now thinking about it, if probe temp reading would be off, it would explain the issue, however, if I define yellowing phase as having no beans with any green color left in them, then that still happens around 6th minute, which according to your expected FC, is late, right? Or is my understanding of yellowing phase off?
Well, clean the sensor and probe first and then try again before analyzing too much.
There is no exact standard I know of in the Bullet community for calling yellow.
It is kind of up to you and how you think of the roast, and as long as you are consistent about it, then your data will be something you can use and reference.
I’ve suggested that aillio make their standard “yellow” phase criteria to help them with their data collection, but it probably doesn’t matter, as there will be trends enough.
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Yeah that’s the same info I read in the forum threads. I cleaned the probe (which was pretty clean even before, but there was a bean stuck to it, not sure if that could cause the discrepancies). I doubt my cleaning will improve anything, but I’ll let you know.
I’ve often had beans get caught between the bean probe (BP) and the door hinge screw. I keep a tool handy to keep that clear between roasts, as it does throw off my BP readings a little. I keep meaning to find a bolt with a different head on it to avoid this.
Most people use IBTS for yellow and FC, but some will use BP for end temp, since it is showing where the beans have been, and the IBTS Shows where they are going, so to speak.
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IBTS is also a lot more consistent for yellow and FC across batch sizes, so long as it is clean. So most people call markings by IBTS, for that reason.
Thanks a lot for the additional info.
One more thing I forgot to mention… my BT temperature, while preheating has rlly big issue getting over 100C, even if I set the IBTS preheat temperature to 250C. Isn’t that strange? I mean I know the probe measures temperature via contact, but still, seems strange. Or is that normal?
I have no issue getting the BP above 100C during preheat.
I think I figured out what’s the issue… I attached the venting system directly onto the bullet exhaust using the vent, so it sucks out all the hot air 
ok, haha, that sounds like a strong fan. lol.
Glad you figured it out!
Thank you for being here to assist. Much appreciated.
THis is my latest roast. Still the time between yellowing and the FC seem off, but given the batch is 300g, the probe reading was much better now.
Any suggestions seeing this?
I mean I can see the red zone is way off, but not sure what I’ve done wrong. I just wanted to do the drop at ~217C, so had to drag it for that long. Maybe I got the FC wrong.
But it could be, that I didn’t do proper preheating? I reached 230C on the IBTS, but only around 140C on the BT. However, it’s been preheating for 15-20 mins. Is there any rule about this? I read somewhere it could easily preheat for 25 mins.
Preheating is complete when the Bullet says “Charge”. Of course you can wait longer, but I believe the bare minimum time to preheat should be until “Charge”.
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I had the same feeling, that there was too much airflow.
I think you can still lower the airflow one setting overall.
The Bullet will get more consistent after more roasts.
It is also important to have really seasoned it with the 3-5 very dark roasts, otherwise the drum is not black enough, and the IBTS will not read correctly.
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Along with everything else that was said, let me state clearly that what you’re hearing isn’t the FC. The FC, on this particular roast, happened around 6:45-6:50, most probably. Give or take 5-10 seconds. Now, the yellowing is when you can’t see any more green beans. It’s not just a little change in colour on some beans. The FC is when you hear pops similar to corn popping, but not when you hear 1 or 2, but when you hear them in succession. Browse the forum on how to hear FC better. Some raise the plug just a bit, some pull out the tryer and some use aids. The SC is more like snapping twigs, but I hope you won’t go that far with your roasts if you have quality coffee. You obviously ran into this with all the excitment possible, and I understand that. Now is the time to stop on a dime, so to speak, and do a lot of reading, watching and learning, before roasting again. I understand people don’t want to state the obvious for fear of other person taking it badly, but I sincerely want to help you. As jacob said, the drum must be seasoned well and there are instructions on how to do it properly on this forum. I don’t know if you’ve skipped the seasoning or simply didn’t connect the roaster to the software when you seasoned it the first time. Everything in life has a learning curve. This is not a plug and play machine. Please don’t get this the wrong way, I’m just trying to help, and you can’t help somebody if you don’t tell them what they’re doing wrong.
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Thank you so much for all the effort you guys put into replying. You are totally right. I got the seasoning wrong, I “re-done it”, I cleaned the machine and did couple of more tests. My latest roasts are rlly good, except for 1 issue I still have and that is hearing the FC. I hear subtle cracking around 180 IBTS, but that is not it. Then I hear much stronger cracking around 200-205C (IBTS). I think I never got to SC as I usually drop at around 215C. Haven’t had the chance to listen to the SC during seasoning - I was busy with getting rid of all the smoke .
Probably the one around 200-205. The end temperature doesn’t really mean much, and you can learn more about that in the Münchow Coffee Mind course, which should still be free for bullet users using the code that can be found on forum here. Just a sec…
There’s much more you can find there, like podcasts, blog, etc. Also, you’ll find a lot of videos on YT by Sweet Maria’s, Rob Hoos and also other bullet users, where you could probably hear what it’s supposed to sound and look like. Once you’ve dedicated a certain amount of time to it, you will be amazed at how the coffee can taste, but it won’t be the first roast. You might like it, but that’s not it. It takes time, but the results are way better than any other roaster in this price range and above, for a fraction of energy consumption. There are automated mini sample roasters that you just push a button and everything goes well, but you can’t do that on a 1kg or larger roasters. Theoretically, you should just find a bean similar to yours on Roast.World, copy the roast, push the button and your coffee will be great. Unfortunately, the reality, once it hits you, is a lot different.
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That sounds about right. You should be hearing FC around 200 to 205C and SC around 220ish if I am remembering correctly
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*on IBTS temps
Amazing content, thank you so much!