For Espresso: Replicating My Typical Profile, FC and 2nd Crack Temps


I have a Bullet R1 coming before the end of the week. By way of introduction, I’ve been home roasting in the garage at my primary residence for 20+ years, first on a 1lb Probat-knockoff sample roaster, and during the last 7 years on a Diedrich IR-1. I only roast for espresso, and now, only single origin Ethiopians, almost always dry processed. My typical roast level is to just before the onset of 2nd crack, which on my IR-1 is typically 419 degrees F (~219 C), supposedly the drum temperature. First crack typically starts at 370-375 F (~188-190 C). The first few pops of first crack might start a few degrees earlier but I disregard the first few errant pops.

I try to get at least 4 minutes (no more than 5) in between the onset of First Crack and the End of the Roast. Typically, I hit first crack at 8:30 to 9:30, and try to avoid extending total roast time beyond 14 minutes, as I have found that 15 minute roasts and beyond produce flat coffee when used for espresso. My batch size is 2 lbs (908 g). I’m not wedded to a batch size of 2 lbs on the Bullet, however if possible it would be great to have the option of 1lb/454g and 2lbs/908g.

I should add that my IR-1 is located at altitude, at around 5850 feet of elevation (~1785 M). I believe that coffee roasts differently at altitude than it roasts at sea level, however I have no experience roasting at sea level so I can’t confirm that.

Anyway, the Bullet R1 is going to be located at a second residence that I use for my business interests, 155 miles away, at an altitude of ~2500 feet (760 M), which I think can probably be assumed to resemble roasting near sea level.

My IR-1 has no automation and I execute this roast profile by adjusting the gas flame pressure and controlling the ventilation through the drum with a damper. I am able to get repeatable results and the loss in weight, from green beans to roasted coffee, is on the order of -15.5 to -16.5%, depending upon the bean but consistent for a given bean.

Of course, this roaster may roast differently and have different results than what I am used to on my Diedrich.

If possible, I would like to avoid re-inventing the wheel and burning through a whole bunch of green beans just to try to replicate a profile that I’ve worked hard to “perfect,” and that I’m happy with on my other roaster.

My questions are: (1) Does this profile seem achievable on the Bullet? (2) do you think the coffee will taste good with this profile on the bullet? (3) Assuming #s 1 & 2, how would you suggest that I try to replicate this profile on this roaster? (4) what would be typical temperatures on the Bullet’s thermometry that would correspond to the onset of 1st and 2nd Cracks?

Thanks for any suggestions and comments!