Outside Environment effect on roast?

Received Bullet V2 recently and have seasoned a few loads and almost ready to attempt first drinkable batch.
I am currently housesitting so did seasoning roasts on back porch in open conditions in Canberra, Australia cold winter afternoon to avoid needing a vent/exhaust setup in garage space.

With the outside temp @ <5 deg C, I assume this will affect the roast profile compared to more temperate conditions? Do I need to do anything to compensate during roast or let the Bullet do it’s thing and it will adjust automatically?

Many thanks

Yeah, leaving behind coffee smoke in someones house is not the way to endear yourself to the home owner! :exploding_head:

Less than 5°C roasting environment will certainly affect the roast profile but I can only speculate what to do to compensate.

  • You’ll lose heat thru the insulated walls of the roaster body;
  • the air drawn in by the fan at the rear will be colder than what you’d experience in partially protected environment like a garage;
  • and don’t forget the beans will (unless stored indoors) be colder too.

Bullet controls manage the power coupled to the drum but not the temperature (except during preheat). Heat loss has to be compensated for by the operator by adjusting power and fan speed. Drum speed can also be used to affect heat transfer from the drum to the beans as the bean mass will be in contact with the drum for a longer time (higher drum speeds) or less time (lower drum speed).

You may be able to solve a lot of the issue very simply by just using a higher preheat setting. Be ready to up the power a notch as 1C starts and expect the roast to take longer than you would with higher ambient temps. 1C/2C/eject temps ought to be substantially the same but the timing will be delayed- it’s really no different than intentionally stretching the roast. And a roast that’s been stretched will likely have a little higher weight loss (a few grams in a 500 gm batch size).

I’ve roasted outdoors a lot with the Bullet and the earlier HotTop; and with my gas fired BBQ+drum roaster at 7,000 ft elevation it could be pretty chilly. But being retired I was able to pick my weather.


Note: If you want to use the tryer you’ll have to keep drum speed at D7 or above as the beans tend to drop short of the tryer at lower speeds.

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Thanks Bruce

Green beans are in a sealed storage tub in Garage and I have started to look at an internal exhaust setup in garage which I think will work fine.

When you say higher drum speed = more bean contact time with drum, is that because of the agitation throwing the beans against the drum wall? I had assumed a slower drum speed would mean the beans are in contact with drum wall for longer?
Cheers for tips

At higher drum speed there is more centrifugal force to pin the bean mass in place leading to longer contact time. Lower drum speeds have lower associated centrifugal force so they fall away from the drum earlier in the rotation. Which is the reason the tryer won’t catch any beans at lower drum speeds.


Ok thanks for that