Advice to prevent scorching

Recommendations for 1kg roasts? I did a Morten Munchow-style full flame 1kg espresso blend last night. I still got scorching and also triggered the Erc 0004 alarm. First crack went straight into second without stopping. Preheat was 310 C.

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Here is the 1kg roast and photos of the beans and chaff that came out the front of the roaster (I catch it in the small bowl).

With the darker roast it is harder to see the scorching, but it is still there on some of the beans.

Those drum speeds look pretty much like what others have measured. I don’t see anything alarming. The difference between D8 and D9 is bigger than the step change at other speeds and typical of what to expect from the Bullet. As I implied earlier I’d rather the difference from D8 to D9 were less, but it is what it is. If you’re catching beans with the tryer it should be fine.

F2 at the start sounds typical of most here.

I’m with @blacklabs - you’re using a higher preheat for a 500 gm batch than I use for my 550 gm batches (482°F vs. 392°F). But then you’re aiming for a specific time to 1Cs. However you’re getting scorching so you may just have to settle for a long time to 1Cs by lowering preheat.

The final temp for preheat is measured with the IBTS only (the bean probe is measured only to assure BT-RoR is pretty much flat at IBTS = preheat setting (approximately… it’s not fine tuned). If the IR sensor of the IBTS is dirty, preheat temp will be higher than you have set. You might try cleaning the IR sensor (after cleaning the front plate).

In order to know when to clean the IR sensor I keep track of the maximum difference between BT & IBTS at approximately IBTS = 260°F. I look for the difference to be greater than 41F° (the difference is sensitive to batch size; a smaller batch will have a higher difference). After cleaning the IBTS the difference is about 45-46F°. Clean with isopropyl alcohol & a Q-Tip; don’t reuse the Q-Tips by re-wetting with alcohol and going back to the sensor again- clean one each time. Roasting snot that gets on the IR sensor doesn’t dissolve with alcohol- it just softens (at beast!). So it takes a few passes.



One other thing: after a roast I take the beans outside and winnow the beans by pouring them back and forth between 2 bowls. Takes a little breeze to work, so in still air you might need a fan to help move the chaff. It isn’t a perfect solution but it works for me.


Edit- wish I could claim winnowing as my idea but I saw it on a Sweet Maria’s video the Thompsom Owen made in early 2019.


R1.10 (Log in | Roast.World) used preheat of 482 F, which is what Aillio recommended for 500g; however, R1.11 used 428F, which is what Royal Coffee appears to be using now for 500g. R1.11 (Log in | Roast.World) used 428F preheat.That hit dry end at 4:41, which is close to my 5 minute target, but then dropped off too quickly. I think a lower PH temp, then soaking, then ramp up to P8 might work as @blacklabs suggested. However, I’m really just getting acclimate by using 500 g batches. I will almost always be doing small sample batches or 1 kg, especially before a market.

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My approach was based on someone else’s (cash0612’s profiles) in these forums initially and then I started tweaking a little. He’s got well over 700 roasts under his belt majority at 1kg batches.

My 1kg batches starts with 572F PH and P9/D9/F3 at time of charge. Now you can’t preset F3 (I hope the team will allow us to do this soon) so I usually will bump to F3 as soon as the control panel allows me to while I drop the beans. Here’s an example Log in | Roast.World

I’ve also started to play around with a 581 PH but with P1/D9/F2 at time of charge to do a bit of heat soaking. I need to play with this a bit more, so far only did 2 such roasts and I’ve been pleased with it. Here’s a recent roast using that: Log in | Roast.World

The roast you posted “full flame style” I think that is too much and I’m not surprised you almost burned your beans given the high PH on top of P9 and F2 all the way - you got a runaway roast. You had a lot of chaff coming out the front because there’s not enough F to pull the chaff into the collector during the roast.

The thing is there is no right or wrong (my personal opinion) it’s what results are you trying to achieve. Take a look at bradm’s profiles, he starts with a 383PH for 1lb roasts. I learned a lot from bradm as well in the beginning. He aims for retaining more fruit and sweetness in his roasts.

I’m 16 months into roasting on the Bullet and just hit 90 roasts (I don’t roast every week). I learned a lot in that time and finally am at a point where I feel like I have a handle on this. I started primarily with 350g batches to get a feel for the machine play around with the settings to understand the impact. I wasn’t as methodical as others in these forums - you can find threads of folks who roast up to 10kg at 350g batches in the beginning to understand how changing the settings affects the cup.

I’m finding my preference is not to rush the drying phase. I try to aim for YP around 5 min mark or a hair longer(333-338F) if I can. I believe this gives a more even cup. If you search for me in RW (select Users and type in my UID or any of the folks I mentioned) you’ll see my 1kg roasts ranges from 10:30 to 13:00 mins long - some of this has to do with the beans and the ambient conditions and how long I want the DT after FC.

I don’t know where you’re located, whether you roast inside or outside. I’m in MA and roast in my kitchen. One thing about 1kg batches is you have to watch the info panel for warnings of the IGBT1 and PCB readings. In my roasting IGBT1 have gone into yellow warning but never red. As you can see from this thread many of us point a fan at the belly and make sure there is ample air circulation.

The journey has been fun for me esp transitioning from the FreshRoast - much more satisfying for me to roast on the Bullet. :slight_smile:

The analogy I always use is with roasting beans you don’t want to put it on high heat to scorch the exterior while the interior of the bean is under-developed. That is fine for searing a piece of steak to get medium rare and the steak would be nice and juicy, not so with beans.


500g roast at D9? that is excessive and coupled with f2 until FC… you are asking for scorched beans and these beans seem to be on the soft side.

The fan is a two tipped sword. It is used to clear out the smoke and chaff. Having it at F2 until the end of the roast will lead to chaff buildup and smokey taste.

The drum speed at D9 for a small roast will lead to the beans getting overdeveloped on the outter shell at the start of the roast and basically get the outtershell burned at the end of the roast.

Drum speed is basically to allow the beans to have a breather each time they flung and even out the roast.

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Aillio says they just leave drum speed at D9. I don’t quite understand how a faster drum speed would overdevelop the outside of the bean. I would think that slower speeds would leave the beans against the drum for longer, increasing conductive heat transfer.

If you think of the centrifugal force created by the higher rate of rotation of the drum, it’s going to push the beans up agains the drum more all around (think of that salad spinner or your front loading washer on max spin cycle). Whereas a lower drum speed the bean is going to fall back into the drum as it rotate up, so whatever bean in contact with the drum falls back more or less into the center creating more of a mixing effect. That’s the best I can describe this (college physics was 30 yrs ago!). I’ve started to play around a little bit with drum speed myself although not as low as the speeds that @otaibimn is using

Yes, I see that; however, Aillio stated in the guide that even D9 is not fast enough to pin the beans to the drum. When I roasted on a Mill CIty 10kg, I was told to adjust drum speed so that the beans were falling at a 45 degree angle across the sight glass. I did a decaf 350g roast today starting at D5 and then gradually going up to D9 at around first crack. Until around D8 I couldn’t get any beans in the tryer. At D8 and D9 I could, so perhaps D9 is not enough to pin the beans to the drum, but does hold them longer. It was really hard (as usual) to tell much about this decaf roast, but so far it doesn’t look scorched. Agtron scores look pretty good too: 51 /69 (whole/ground). I’ll post details as part of this thread later.

Looking forward to your cupping results. For me at D7 I have to hold the trier at 10 or 11 o’clock for a little while to catch some beans. I’ve not gone lower than D7 yet.

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I have been roasting for market for a few summers and ultimately have settled on 800g batches. My preheat is usually 280c, which allows for about 3-5 minute lag between dropping a batch and starting the next one. It may depend on your approach, etc. But I have also found that when I need to roast 20+ batches in a row, I’m much more comfortable going at those preheat temps for long periods.

Glad to hear it sounds like one of the profiles turned out well! I think I’ve struggled to avoid tipping more than scortching, but i feel like i often have similar trouble on induction cooktops cooking eggs. Im currently following a Rob hoos box set for the Bullet… He used a 210c preheat for his 500g batches, when I used his profile, I was definitely lagging… but when I upped my preheat to 220c, I would up with 10pts darker agtron… still straightening it out in my head, but his insights have been pretty valuable. Also, it seems like some other people have the same issue as I do, while a few do not. Perhaps it’s just conditions, perhaps some Bullets have a little different power output.

I’ve been practicing some 500g batches the last couple weeks to get more feel for his approach, and it has been having some good results. I will try to link a recent one here. This is a catuai anaerobic natural from Costa Rica roasted yesterday.


Is Rob still doing this? Sounds like a great way to learn the roaster and more about roasting. For scaling up, I have two choices: a drum roaster (wehther in my own roasting space or coroasting where I can arrange to use a Mill CIty 10kg, or Dietrich IR-12), or something like the Artisan Xe that requires a lot more power. The trouble with electric for me is that I cannot trust our grid. According to Ken (at Coffee Crafters, the maker of the 3e and Xe FB air roasters) a 10 volt drop is significant. With the bullet on the solar genny I have no worries about a drop in voltage or power outage.


Based on my results above, Aillio’s suggested 350 g light roast, and suggestions from others above, I created a recipe for a 350 g roast of some old decaf I had laying around. I modified Aillio’s suggestion by lower PH temp and then using @otaibimn suggestion to decrease power, but increase drum and fan speed throughout the roast. The result was this:

The roast was faster than I like, especially for decaf that tends to get too dark on the outside while being underdeveloped inside. My target for most beans is dry end at 5 minutes and first crack at 9. For decaf I sometimes add 1 minute to those times. Agtron whole/ground was 51/70. Not a bad delta for such a fast roast of decaf beans. I also did not notice any scorching or tipping, though it is hard to tell with decaf. I marked dry end simply by temp (160 C), because there was no real change to yellow during the roast.

I could not get any beans in the tryer until late in the roast when the drum speed was up.

The roast is here: Roast World - Cup, grade, and analyze your coffee roasts in depth

Recipe was:

Tomorrow I will try another 350 g roast of a different decaf, but I will lower PH by another 10 C to see if I can draw out dry end and first crack.

Instead of lower PH temp, I tried another roast with the recipe above with 50g more coffee. This time I went back to the Costa Rican. This time I hit yellowing at 4:33, but then the roast started to slow too much so I bumped power back up. Despite this, I still ended up with scorched beans. Photos of beans were taken using a macro lens. Once again, during the roast I noticed a lot of burnt chaff through the sight glass.

The beans:

Cup it and taste it.

Give the same profile a decent soak at the start. 1 min of P4 let us say (Up the preheat by 10-20 degrees to compensate with initial momentum).

The rest seems okay.

IBTS and Bean curves never touching means that there is enough power for a decent soak.

I have a suspicion is that the beans might be too dry since they are old.

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I’m with @otaibimn about lower starting power setting.

And “dry beans” is probably right on the $$! (I should have caught that since it’s such an issue here in SE Arizona.)


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Not sure if it matters, but I get no scorching on these beans in my Artisan 3e fluid bed air roaster. I usually do 2 lbs on that so that it tightly follows the set profile. Here is an example from 7/13/22:

The squiggly green line at the bottom is the burner control, which runs from 0 to 100 on the left Y axis.

Fluid Air Roaster = Convection no conduction.

The quality of the bean and it’s storage is important to roast on drum roaster.

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@toddjohnson I am not sure you can completely compare your bean appearance between your Artisan fluid bed roaster with the Bullet. As @otaibimn said, they are completely two different types of roasters. I came from a FreshRoast to the Bullet so I have some familiarity with an air roaster.

FWIW, here is a picture of the beans of my recent Peru roast which appears to have similar profile as yours above in terms of the PH, P and F settings but at 632g (leftovers :slight_smile: ), with the main difference being the D settings.

I am hoping to persuade you that appearance isn’t everything, it’s the cup result :slight_smile: In an air roaster the appearance will be more even.