How to Begin Roasting Great Coffee on the Bullet R1 V2

10 min readApr 19, 2019

Please note: Before you begin to roast coffee on the Bullet R1 V2 you MUST read the manual. This article assumes you’ve already read it and have a grasp of Bullet-specific safety precautions and vocabulary. So if you haven’t already, then please head over to, where you’ll find links to the manual as well as to other Bullet R1 roasting resources such as this one. Also note that the recommended settings given in this article are only for V2 Bullets. V1 and V1.5 Bullets employ different parts and so behave differently. Contact Aillio for more information.

The roasting process is incredibly complex, involving thousands of chemical reactions occurring simultaneously, and even slightly different approaches to roasting the same bean can result in big flavor differences in the cup. This is exactly what makes the craft of coffee roasting so interesting. It’s also why we’ve built the Bullet in a way that allows users to exercise a great deal of control over their roast.

But by giving users so much control, we also introduce more variables. If you’ve never roasted coffee before, then, roasting on the Bullet R1 may feel a bit overwhelming at first. There are many, many little decisions to make, and each one will impact your roast. But don’t worry. With a little foreknowledge, you can begin roasting excellent coffee from day one.

How Much Coffee Should You Roast?

In the beginning, we urge you to pick a specific batch size, (350 or 500g are pretty good ones for learning), and stick to it for your first ten roasts. Batch size is perhaps the easiest variable to control, and by sticking to the same batch size early on, it will be easier for you to learn how Preheat, Power and Fan settings interact to impact the roast.

What Preheat Temperature Should You Set?

Before you roast coffee, you must preheat the drum. The Bullet R1 allows you to set a specific preheat temperature before every roast — a necessary feature if consistency is important to you. Think of coffee roasting as being like following a recipe for a holiday ham — you wouldn’t expect that ham to come out the same if you change the preheat temperature, would you?

Learning how to manipulate this variable is crucial to gaining control over your roasts. Simply put: how high you set your preheat temperature will likely depend on how much coffee you plan to roast, as well as how dark you intend to roast it, in any given amount of time. If your preheat temperature is too low for your batch size, you may struggle to finish the roast quickly enough, leading to less flavor in the cup. If it is set too high, your roast may spiral out of control, resulting in undesirable flavors.

General Recommendations:

For 350g you can try setting the Bullet to about 220ºC. When roasting 500g, that can rise to about 250ºC. For 750g, try 280ºC. 1000g roasts should probably begin at the max settings, 310ºC.

These recommendations are only starting points. There are many different paths up the same mountain. You can find a more detailed table of suggested preheat settings, including Fahrenheit temps, down below. But don’t feel afraid to try roasting outside the recommended ranges.

Which Power Setting (From 1 to 9) Should You Use?

The Bullet R1 is a powerful machine, and you can roast a lot of coffee very quickly on it. But getting to the finish line as quickly as possible is rarely the goal — if it was, there would only be one power level on the Bullet, the highest. Instead, there are nine. This is because roasting different beans in different batch sizes at different power levels for different durations will inevitably lead to different flavors. Making wise power adjustments during the roast is crucial for bringing out particular flavor notes and getting the best from your coffee.

There are many strategies for manipulating power during the course of the roast, but there are two general concepts most roasters keep in mind at all times.

1. Smaller batch sizes will require less energy and therefore less power than bigger batches.

2. Setting a higher or lower preheat temperature will also affect how much energy you need to add while roasting. The lower the preheat temperature, the higher the power settings will be.

General Recommendation:

For charges of 350g or less, you may want to begin as low P5. For a quicker roast — particularly with a lower preheat, you can experiment with as high as P7. For a 500g batch, P6 or P7 may be more appropriate. 750g could begin with P8. 1000g should probably always begin with P9.

Commonly users will begin with a high power setting (P8, for instance) and then begin slowly dropping the power as the roast continues (see below, under the “Roast Recipe” section for a specific example of this strategy).

That said, there are no hard and set rules here. As you become more familiar with roasting coffee on the Bullet R1, your power settings will likely become more fluid. You will learn how to react to changes in real-time, or even to anticipate them before they occur.

Which Fan Speed (From 1 to 9) Should You Use?

The effects of fan speed on roasting are complex. At lower (1–3) settings, boosting the fan speed during a roast may actually increase convection heating and quicken the roast. But as the fan settings move higher and higher (4–9), the air flow within the drum increases signifcantly, allowing the user to put the brakes on a roast that is moving too quickly.

General Recommendation: Oftentimes, users will begin with a lower fan setting (1–3) and gradually raise it over the course of the roast, though it is rarely necessary to use the fan at full power. Again, see below for a specific example of this strategy.

Which Drum Speed (From 1 to 9) Should You Use?

Perhaps no variable in roasting is as poorly understood as that of drum speed. The fluid dynamics of beans tumbling in a drum is more complicated than you would imagine, and its impact on heat distribution even more-so. Although there are some competing theories among roasters, most agree that too low a drum speed increases the probability of a roast defect known as “scorching”, as too much conductive heat too quickly may burn the outside of the beans. Conversely, due to centripetal force pinning the beans to the side of the drum, too high a drum speed may also yield the same result: scorching. In the Bullet R1, however, the drum speed will never reach such a high setting. So as long as you select a drum speed above 6 or 7, you should be safe.

General Recommendation: Set a drum speed of at least 6 or 7 when beginning. In our office, we tend to use a default of D9, the very highest setting, and only experiment with lower drum speeds on small batches of 350g or less.

How Dark Should You Roast?

You probably already have a preference for the darkness of your coffee roasts. There are several ways to quantify roast darkness, with color and end temperature being the most obvious ways.

But there are two key events during the roasting process that roasters tend to use as markers for communicating the darkness of a roast to each other. Both of these events produce cracking sounds similar to the sound of popcorn popping. “First crack” occurs when moisture within the coffee bean that has turned to steam builds up enough pressure to escape, causing it to rapidly expand before bursting. “Second crack” occurs as the coffee bean structure itself begins to collapse, and it is again marked by a cracking or popping sound, oftentimes louder than the first crack.

You should begin preparing to hear first crack after the Infrared Bean Temperature Sensor exceeds 190ºC. Listen carefully, as some beans are difficult to hear crack. In most roasts, first crack should occur between 200ºC and 210ºC. Second crack tends to occur about 20ºC higher.

A very light roast will end just as first crack begins, while any roast taken beyond second crack will be considered dark. Of course the darkness of a roast has a huge impact on the flavor in the cup, with darker roasts (for better or worse) tasting more generically ‘roasty’. Those traditional roasty flavors, although favored by many, tend to come at the expense of some of the more unique flavors found in lighter roasts.

For this reason, most specialty coffee roasts will end somewhere before second crack, with many roasters preferring light roasts for filter brews and medium roasts for espresso drinks. Darker roasts are more common in commercial coffee, though they are not unheard of in specialty. It’s all a matter of preference, and you should never let anyone tell you what’s right or what’s wrong. Trust your taste buds.

How Long Should My Roasts Last?

The speed at which you roast your coffee also has a dramatic impact on its flavor. The majority of specialty coffee roasts last between 7 and 12 minutes long. While there may be exceptions — particularly if roasting large batches very dark — in general it’s a good idea to keep your roasts within these time constraints. If you roast coffee too quickly, some of the flavors may never have a chance to develop. If you roast coffee too slowly, you run the risk of dulling those same flavors.

Putting It All Together…

The table below should look familiar, as it is taken from the manual. It summarizes some of the preheat and power suggestions above. Again, please keep in mind that you are encouraged to experiment with settings outside the recommended ranges. In the end, it’s what the coffee tastes like in the cup that matters most.

A Beginner’s Roast Recipe

A roast recipe is a set of guidelines for finishing a roast in a particular way. A good one will take into account all of the information provided here — and more.

With that in mind, we offer you a recommendation for a Beginner’s Roast Recipe. As with any roast, you should expect to tweak it according to the bean you are roasting and your own tastes, using the concepts described above.

Also please keep in mind that these settings for those roasting on V2 Bullets, which have both the IBTS installed and the new V2 induction board, which has more power. The fan settings are also for those who have calibrated their fans.

Roast Level: Light (For Filter Coffee)

Weight: 350 grams

Preheat: 220ºC

Charge Settings: Power 7, Fan 2, Drum 9

Infrared Bean Temp@120ºC: Power 6, Fan 3

Infrared Bean Temp@165ºC: Power 5

Infrared Bean Temp@190ºC: Power 4

Infrared Bean Temp@200ºC: Fan 4

<First Crack Begins@202–206ºC >

45–90 seconds after First Crack: End the Roast

Making Adjustments

To learn faster, it is a good idea to only change one variable at a time. In other words, if after performing the Beginner’s Roast above you feel that you reached first crack too quickly, then you should either experiment with lower power settings during the roast, or a lower preheat temperature. The reverse is also true: If you want to reach first crack quicker, you should either use higher power settings during the roast, or raise the preheat temperature.

Roast Profiling

We’ve given you some general guidelines to get started roasting coffee, but we haven’t discussed the possibilities unlocked by roast profiling. We strongly urge you to take advantage of them.

RoasTime, the Bullet R1’s roast profiling software, allows you to both monitor and control your roasts by plotting bean temperature over time. While it is not necessary to use RoasTime to roast great coffee, there is a lot of value in the data it generates, particularly if you’re interested in obtaining consistent results. With a little practice, your ability to visualize roasts as profile curves will become a valuable tool.

RoasTime is a work in progress. New features and improvements, based off user feedback, are being added on regular basis. If you’re serious about roasting coffee, you will benefit greatly from the software. You should begin using it from day 1.

Read more at: How To Use RoasTime 2.

Going Further

Connecting with other Bullet users is perhaps the best way to get the most out of your Bullet R1 experience. The more information we share with each other, the better our coffee will become. The Roast.World platform provides a space to do just that. You can view, comment on, download, and automatically playback the RoasTime roast profiles of other users, and even find suppliers for particular green beans. The built-in Roasts Analyzer will also allow you to compare your roasts, or the roasts of others, to each other.

Like RoasTime itself, Roast.World is a work in progress, with a great deal of planned improvements expected to be pushed through in the coming months.

There is also a thriving unofficial Bullet R1 Facebook group, and a separate online forum just for Bullet owners,

In addition, there are many other coffee roasting resources available online, from articles written by professional roasters to forums devoted exclusively to home roasters. There have been a great many books published on the subject, as well.

In your readings, you may discover that different people have different opinions about how to roast, or about what makes a great roast. Ultimately, there is not a great deal of consensus out there. And it may be that what is sometimes taken for granted as ‘good’ or ‘bad’ really ought to be re-examined.

There is still a lot to learn — even among experts. So experiment, and have fun.