Underdeveloped Roasts

I’m a new Bullet R1 owner, but have been roasting on other machines for about 16 years. I progressed from an air roaster, to a Behmor, to a Gene Cafe, to a HotTop, and now to a Bullet - hoping to take my abilities to the next level. I’m afraid I feel like a complete novice, and haven’t been able to roast a drinkable batch, much less a decent one.

I’ve dug through this forum, read Scott Rao’s Coffee Roaster’s Companion, picked the brain of a professional roaster at a local coffee house, and experimented on my own through 20 different roasts. I’ve tried following the beginner’s roast in the Bullet’s manual, as well as various roast profiles from users on this forum.

Each time (even when I push through to mid-2nd crack), the coffee tastes grassy, underdeveloped, and frankly, terrible.

Has anyone else endured this plight? I’m quite bewildered at this point, almost to the point of trying to return the machine. Any guidance is much appreciated!



I’m less experienced than you and I’ve just completed seasoning the roaster. But I’ve also noticed from a color standpoint, I’m not able to achieve a dark roast. Perhaps someone can assist us?

Tom, I’ve been roasting for 20 years and been through many different roasters, but mainly focused on Drum-roasting throughout. I can tell you that moving to the Bullet last March was like having to learn how to roast all over again. I believe that the presence of all these new controls (that we have on the Bullet) is partly the reason for it. I was way past the first (20) roasts before I was getting what I considered satisfactory results, so don’t feel alone.

What I ultimately had to do was basically throw-out much of what I’d learned on other roasters. I too have Rao’s “Roaster Companion” book and it is a great resource. Especially from the perspective of developing the roast now that I have visual data. I do think of roast development as the entire window of what I’m doing to the beans from start to finish.

The grassy and underdeveloped result is an indicator of needing to learn how to use the Bullet’s controls to affect roast development. Scott Rao made an excellent statement in the book about “don’t roast darker to mask problems with roast development”. I know that it is tempting to do that, but with the Bullet you now have the ability to actually drive and effect the roast (with data feedback) throughout the roast.

In the end, I’ve learned to greatly adjust my method with the Bullet vs anything I’ve done in the past. A new roaster of this capability caused me to hafta admit that I had a lot more to learn regardless of my roasting tenure. Tom Owen’s Bullet videos over at Sweet Marias were very helpful and I also went through the whole series of roast education videos on “Mill City Roasters” YouTube channel. I did that because it occurred to me that (now) I have a roaster where I can apply both data and roasting knowledge in some new ways. I believe that all of it (collectively) affected how I looked at coffee roasting on this particular machine.

Don’t send your machine back. Invest in learning how to use this new tool and you will be rewarded. It just takes time and a fair amount of roasts. :sunglasses:


I am a newbie with the Bullet also, but have successfully seasoned the drum with roasts that went way past second crack, but the very first seasoning roast I did never developed past yellowing because the power settings were set to low. After preheating is finished and you dump your beans you can adjust the power settings to 9 and keep your eye on the window.

Thanks PapasCup. It certainly has been a humbling experience. The most frustrating aspect is that when I compare my roast profile to a Rao example, or profiles from other trusted sources on this forum, they don’t look much different. I guess I chalk it up to, “I don’t know what I don’t know.”

I’ll check the videos on Sweet Maria’s (I suspect many of us end up with a Bullet by being loyal SM’s customers), as well as Mill City.

Again - thanks again for the insight. It is comforting to know others went through the same learning curve!

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It may be useful while all of you are “getting your sea legs” to share some details about what you are doing with your roasts. Qty of coffee, pre-heat setting and what heat setting(s) you are using from start to finish. Also, when is 1st C typically occurring, total roast duration, etc. A screen copy or link to some of your recent roasts in RoastTime would also be useful. That way the folks here that have been using the Bullet longer can get an idea of what is happening during your roasts.

I’m not an expert on the Bullet, so what I’m sharing is simply my opinion as you develop your own skills and preferences. My best suggestion would be to get a good plan toward managing heat across the entire roast without focusing as much on drum speed and fan (for now).

I usually do 1lb roasts on my Bullet. Here’s the basics of what I’m doing these days for most roasts that I do (every 10 days). It is producing good results for me. YMMV depending upon tastes, but this may help you get an idea of what I’m doing to manage heat/heater settings.

  • I use a 455F preheat. I wait for the Bullet to stabilize and announce "Charge". The default Heater settings (at Charge) is P7, but as you will see I manage that heater downward at certain intervals.

  • Fan is F2 and Drum is 10 (throughout).

  • In the software that I use (Artisan), I have a command setting the Bullet to immediately drop heat to P1 for 1-minute after Charging the drum with the beans. I’d need to yield to others here that can comment on their settings who use the RoasTime software.

  • After that 1-minute ends, I set the heat to P8 and ride at that setting until Dry-end is reached. I’m visually monitoring Dry-end through the window of the Bullet’s door. Dry-end typically happens between 4-5 minutes at my heat setting, but it can vary depending upon the bean/varietal. I’m not a fan of constantly using the Tryer because I can easily see the bean’s progress through this stage via the window.

  • When I reach Dry-end, I drop the heat to P7 and run that way until the Bean temp hits 350F.

  • At a 350F Bean temp, I drop the heat to P6 and run that way until I hear the very 1st snap of 1st C. I’m still experimenting with finding the best point to drop the heat ahead of 1st C, but do know that it helps avoid a 1st C “flick” on my ROR.

  • When I hear that very first snap of 1st C, I drop the temp to P5 and ride that setting all the way through Full City or the first snap of 2nd C. Depending upon the bean, I often don’t allow the roast to enter 2nd C to preserve unique flavors. I do use the Tryer as a visual tool when I’m approaching 2nd C. I want to check the surface of the beans for smoothing which tells me I’m closing in on 2nd C.

  • Dump beans to cool and stir with a wooden spoon to aid in cooling as quick as possible.

Of course, I watch my ROR curve as an input tool, but I also don’t worry if a given varietal doesn’t precisely behave (ROR-wise). One thing that I’ve learned about ROR and the Bullet. I have to anticipate ROR and think ahead of what the beans will do when implementing a heater change. I decided to focus upon power usage and timing of roast development first vs tinkering with drum and fan speeds. That is coming though and I look forward to experimenting more with those controls.

Hope this helps in some way, but you’ll still need to find what works for you and your tastes.


Here’s a graph of a recent roast (from Artisan). May be too hard to pick out details, but thought I’d share it as a visual to go along with my roast process above. There are many more people here using RoastTime, so they may have some better captures/data to share that aligns with the software that comes with the Bullet.

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Just finished this roast. I pulled an espresso, and it’s the best roast thus far. Another user privately messaged me a profile he pulled from Sweet Maria’s. He encouraged me to avoid religiously adhering to the Rao’s “always declining RoR” mantra, which I did for the first time. This cup still tastes a bit underdeveloped, but there’s some progress. I’m hoping the slight grassiness and astringency mellow overnight.

One consistent theme in your advice above and from the other user is that it seems I’ve been using too little power early on.

Tom, I’m glad your recent roast was better.

Papas has covered most of the bases and I like his suggestions. My only addition would be to try a roast using a higher pre-heat temp…I usually roast 454g (1 lb) and set pre-heat to 230C…wait for the “charge” command…can take about 25 minutes of preheat to get all parts of the roaster ready, depending on your environment temp.

Thanks for the RoastTime graph. I see a couple of things from the graph.

  • 1st (as wngsprd pointed out), the Preheat needs to be raised. When I was struggling to get better roasts from the Bullet, one big thing that I discovered was that my Preheat was too low to get the initial momentum needed. An adequate Preheat helps by having the drum temp high enough so that the beans can properly roast (interior and exterior) during the Drying period (first 4-5 minutes). That is crucial to getting the best flavor from the beans and is hard to accomplish without enough heat.

  • 2nd, I can see that the absence of enough heat at the beginning of the roast is producing the need to increase heat settings through most of the roast. It should be the opposite with declining power/heat at key points. That is also reflected in your ROR where the roast is basically flat-lined until FCS. That alone can produce the off-flavors that you are seeing.

I do recognize that “ROR religion” for the sake of believing in something without understanding isn’t the best method. However, the reason that the ROR principle works (IMO) is that sufficient initial heat has been provided to drive the bean temp to a high enough point that will gradually decline as the beans absorb heat and require less from the heat-source. That is basically what also produces a nice decline in the ROR graph. I’ve had nice roasts that suffered from a “flick” or “crash” while I was learning to manage heat on the Bullet. But I drank 'em anyway…:sunglasses:

In all my years of drum-roasting, because I had no visual data, I had been using Rao’s basic principles without knowing it or him. Getting the Bullet with all the additional information (graph, watching the beans as they progress and using the Tryer has helped me to better understand how a roast develops.

Lastly, managing ROR is nothing more than understanding ( and properly reacting) to bean development through the entire roast process. When I first began looking at ROR (with the Bullet) I felt like it might just be unattainable and I didn’t understand how to affect it. That is where the YouTube video education from the folks over at “Mill City Roasters” really helped. They do a great job of explaining bean development during the roast that really helps understand Rao’s ROR principle. To me, ROR is really a good sense application that could found in many good roasting principles. Scott just made it a mainstream term IMO. :grinning:

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Papas -

Here’s the latest. I went with a higher charge temp, and produced a slightly more desirable roast curve and beautiful looking finished product (even roast, no tipping or scorching, didn’t looked baked, etc.). I tried to stretch the development post FC, but I still have grassy, astringent tasting coffee. I choked down half a cup, but that’s about all I could take…

I guess I’m going to spend the evening looking at Mill City Roasters YouTube videos. Thanks again for the insight.

IMG_8435 Simply had to thrown this out.

If I had a lb of beans for every time I failed trying to get my Bullet to do what I wanted it to…:crazy_face:

It does take time with a new machine, new technology, software controls, etc. It is hard coming from success on previous roasters for years into a new roaster and finding that things don’t work the same. The principles of good roasting techniques don’t change, but differences in roast equipment can be a challenge to master.

Out of curiosity, are you on one of the new V2 Bullets or its predecessors V1, V1.5 (which I have)? I ask that because all of my experience on the Bullet comes from using a Bullet 1.5. It occurred to me that there could be some differences on a V2 that I just don’t know about.

Back to your current progress. In your latest graph, there is still some opportunity for roast management improvement.

  • I see that your Preheat is now set to 455F (good stuff).

  • Try going to P8 at the 1-minute mark (instead of waiting 2mins into the roast).

  • Drop to P7 immediately when you see Dry-end (or the “YW” point on your graph). Keeping the Heater at P8 all the way to just before 1st C began to grow is applying too much heat to the beans during the period from Dry-end to 1st C. It is also what causes the “flick” (or spike) in the ROR at the ~6min mark.

  • When your bean temp reaches 176C (350F), immediately drop to P6. This drop helps further reduce the roast temp in anticipation of the beans going exothermic as they do right before 1st C.

  • When you hear the very first snap of 1st C, drop the Heater to P5.

  • Unless you are shooting for a dark roast that produces a lot of smoke in the drum leave the Fan at F2 throughout until Dump (for now). One qualification though: My Bullet does not have that Fan range change that Aillio implemented several firmware releases back. So, F2 on my machine could be very different than F2 on your Bullet if that firmware change is in your Bullet.

The Mill City videos were the baseline of how I solved this oft encountered problem that you are having with this new machine. Armed with good bean development knowledge, it then becomes a task to get the Bullet to accomplish it for you.

One last thought. Maybe try one of the RoastTime profiles that some of the other veterans here have shared. That might be an easier baseline way toward finding what tweaks you may have to make to adjust the outcome to your particular tastes. Keep at it because “there is light at the end of this tunnel”. :coffee:

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So here’s the roast profile from last night, about 1:30 AM. Ironically, I roughly followed much of this advice. I feel like I’m zeroing in on some of the adjustments. I’m starting believe two things: (1) I was overcorrecting initially, placing too heavy of a reliance on the inherently lagging RoastTime graphs, and (2) the Bullet takes longer to season than 3 - 5 roasts. I know I’m learning and refining my skill set, but I’m not deserving of all the credit. Most importantly, my coffee this morning was actually quite good!

I took an admittedly safe route by brewing with a Chemex - which I think is more forgiving than pulling an espresso (my standard brew). But I’m now drinking an espresso with the same roast, and it’s not bad at all.

Also, I’m roasting on the V2. I can’t say if the V1.5 is any different

Best advice? Don’t get wrapped around the axle over ‘Roast Curve’. Sweet Marias posted an Award Winning curve that was counter-intuitive the Rao mantra.

I am a 20-year Westbend Poppery roaster year and have had my Bullet almost a year. Bad roasts/terrible coffee can be counted on one hand.

I just got done with a Kenya Kiaga AA - I RARELY go past 15% RDev (1 minute or so after FCS).
I have some great results with Kenya coffees when I keep RDev at 12% and my wife insists on Kenyas, now.

Preheat is usually 230C. I usually roast 450g batches.

Start fiddling with ONE parameter at time. Find yer feet with that parameter then, start fiddling with another, and so on.

My biggest challenge lately is trying to go darker and have a decent cup.



Thanks, John. I’ve definitely backed off of strict adherence to the roast curve. It tended to lead me down the road of continuous “corrections”, without having the experience to understand the results of what I was doing.

My last roast was decent (though far from what I was able to achieve on a HotTop roaster), so I plan on employing a more systematic approach as suggest - starting with only tweaking heat input.

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I didn’t see you mention it in your earlier posts; have you looked at Aillio’s Medium article about getting started with the Bullet?

My original problem with the roaster were that I set the PH temp too low for the amount of coffee I was using, so initial dry was getting stretched out, and then I was trying to micromanage the roast around 1C, leading to some wonky curves and coffee that was drinkable but not great.

Now for a 1lb charge I PH to 250C, set the toaster to P7, F2, D9, and let it run without fuss til the IBTS reads about 185-190C. From there through the start of 1C I bring the fan gradually up to 4 and the power down to 6 and then 5 depending on how I want to finish.

With this I get a nice gradual ROR backoff through the entire roast and the end product is quite nice.

You might want to see what combination of PH and initial heat allows you to get your roast launched so fewer setting changes are required through your roast. If you’re trying to chase a desired result using the controls, you’re likely to overshoot back and forth.

Keep at it, and best of luck!