Adapting Bullet roaster to Sonofresco recipes?

Hi everybody! Ethan from Mountaintown Coffee Roasters here. We’re a small roastery located in Ellijay, GA, US.

Our primary roasting machine is a Sonofresco CR2, but we really like the Bullet and how configurable and versatile it is. Our question for the community is this: How do we match our roast levels between our two machines? The CR2 basically has six roast levels that we use, 0-5, but obviously these settings don’t translate exactly into building a Bullet recipe.

The CR2 does come with a temp/time chart ( page 25), but we’re still not exactly sure how to take that data and plug it into the Bullet in a way that makes sense. What we’ve tried so far is preheating the Bullet to 200c/392f for a Sonofresco level 2 and 210c/410f for a level 5, which are the roast levels we use the most on the CR2. This seems to do ok, but we also feel like we’re missing some important steps.

Has anybody else adapted recipes like this? We appreciate any insight the community can offer. Thank you for reading!

If I understand correctly it the Sonofresco is similar to the FreshRoast but bigger, therefore fluid hot air roaster. I came to the Bullet from the FreshRoast and I will say this much - it is very different way of roasting. I had to learn how a drum roaster works. I think your profiles between the two is going to be different. In the fluid air roaster you can control the air flow and heat, but in a drum roaster you have the hot metal drum to contend with which will retain heat longer even when you drop the power in the Bullet. I don’t know how you’d “translate” between the two, TBH, it’s two very different machines.

Happy Roasting.

You didn’t indicate what size charges you typically roast in the Bullet but my normal roast is around 570 gm and I preheat to 235C. Unless you’re roasting samples (250-300 gm) I think a 230C preheat might be a bit low.

depends on the bean IMO; for a softer/less dense bean a lower PH might make sense, but agree that 200C on a bullet v1.5 or v2 is on the quite low side for a 1 lb batch

just another datapoint, I use 235C as my default for 455g batches

the first roast guide has a PH vs batch size guideline table, I think

@blacklabs summed it up well…it’d be great if someone did this work already and could give you guidance, but my guess is it hasn’t happened, so you’ll have do some controlled experimentation on a lot of cheaper coffee to learn how the roast parameters correspond between the two roasters. It’d probably be easier if you were looking at trying to do this with a Sonofresco and an IKAWA. If you can figure out how to do that more generally, you might be onto a career as a roasting consultant :smiley:

Hey GA Mtn Coffee,

I think you will do yourself a disservice by trying to adapt the Sonofresco recipes to the Bullet.

All roasters are different and the Bullet, especially, is different than the Sonofresco. The roaster is your primary tool, and as a craftsman you need to know your tools. You need to spend the time and waste the coffee beans to really understand how your new roaster works.

The Bullet manual has some sample roasting recipes. It also has suggestions for preheat temps for different charge sizes. These are good places to start.

Since color is, by far, the biggest determinant in the final flavor of the coffee, you should probably start there. IBTS temp is very good proxy for color for a particular bean variety and is largely unaffected by charge size, preheat. ambient temp or how many roasts you’ve done back-to-back. As BAB keeps reminding us, just remember to keep the IBTS sensor clean!

Do several roast of the same bean, dropping them at different IBTS temps until you find the IBTS temp that corresponds to the color/flavor you’re going for. If you have a roast color analyzer - even better. By focusing on IBTS temp, you can largely get to the same flavor, irrespective of the other variables in the roast.

Then you can start playing around with power/fan/drum speed to hit the roast milestones in the times you think best, remembering that time to FC is not very important; time from FC to dump is somewhat more important, but neither is anywhere near as important as final color (temp).

Don’t get caught up into trying to micromanage your roasts - good, solid scientific research has shown that all this mishegoss surrounding RoR and trying to maximize or minimize time spent in certain phases is virtually untasteable - certainly by your customers. Just don’t do stupid things like putting a little bit of coffee in a very hot drum so it scorches. Again, the recommendations in the manual for preheat are a very good place to start.

The basic recipe that I use for most coffees that I roast for myself is -
Charge - 500g
PH - 250°C
P8, D9, F2 —> 2:30
P5, D9, F2 —> 200°C (IBTS)
P3, D9, F2 —> 215°C (IBTS) —> dump

My goals are -
Hit FC at 9:00 give or take a minute (not terribly important)
4 mins from FC to dump

Bear in mind I make my coffee in a vacuum pot; don’t much like espresso; drink it with a sprinkle of sugar and a bunch of half ‘n’ half and am not some sort of golden tongued sensorial wonder.

Obviously, some like it darker - even burnt - and some like it blonde. [shrug] You know your clientele and can adapt to meet their preferences.

At any rate, it’s a place to start.


Hello all, we appreciate your replies! For the batches we’re roasting in the Bullet so far, we’ve typically been doing 6oz / 170g charges. They’re test batches for coffees we haven’t started roasting in the Sonofresco yet.

We will keep experimenting! Thanks again for your time.


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Hey Ethan,

Forgive me if I am just restating the obvious - about the only thing that will be transferrable from your 170 g test batches to your final recipe is the color, for which BTS temp is a good proxy. Preheat, power, and and drum speed will all be batch size dependent, as will timing.

Not to say that what you are doing isn’t worthwhile. It is, absolutely, because you will establish what the ultimate drop temp will be, irrespective of batch size, and that is your most important roast parameter. (While it is doable, 170 g batches are very hard to control, which is why I suggest just focusing on the drop temp/color, which you can control absolutely, and not the timing.)

I suggest maybe purchasing some really cheap beans and roasting batches that are the size you are ultimately wanting to roast. This will let you to get a feel for the thermodynamics of the Bullet. While not an exact match for the beans you want to roast, this will give you a departure point for creating a recipe to hit your milestones at the times and/or temps you want to.