Impact of Roasting Room Humidity (RH) Level on the Bullet R1

I have completed a completely unrelated project to better control humidity in the whole house to under 50%. Required new Dehumidification Equipment as well as HVAC controls modifications. I was curious if this would have any effect on coffee roasting. My first 12 roasts on the Bullet with humidity controlled to under 50% seemed to run faster (quicker to first crack and dump) than they did when my roasting room humidity was 60%-65%. I have not done an in depth analysis so not scientific yet. I will be monitoring this as I do further roasts.


Very interesting.
It will require more energy to heat up the water molecules, but if this is why you are seing faster roasts with less humidity I don’t know. Any difference in taste?

Jacob, I can not yet speak to taste as it will be a while before I drink any of this batch. I also have the disadvantage of thinking everything I roast taste great. I have to reply on my wife to discriminiate among various batches.


I’m sure Therese would be interested in the results of this experiment…


I live in South Florida, close to the coast. On any given day, its between 84-96 degrees Fahrenheit, or around 32 degrees Celcius for my wonderful metric friends (I cannot stand the US Imperial System). I currently roast outdoors on my back patio, in the shade, however the current relative humidity is avg of 91-93%…rather ‘moist’ and wet. I typically will bring my little piggy under my arm (My Bullet R1) and set it up and leave it outdoors for about an hour before I plug it in…giving the components a little time to acclimate to the atmospheric conditions. A lot like when you are shooting photography between indoors and outdoors, you must give your lens a chance to acclimate. After about an hour, Ill plug in the R1, and let it PH for at LEAST 30-45 minutes. I find that by doing so I can skip the dreaded ‘first roast was shit’ syndrome from not having enough thermal dynamics to transfer the necessary heat into and out of the bean cellulose. I may be currently spoiled with my atmospheric conditions, which i feel might lend a hand to helping me roast without as much temperature nuance and fluctuation. Im also at sea level, around 0ft (0 meters). PS: Did I mention I love you guys!

Bob, dont you have about 18-20 feet of 6" ductwork that you vent to the outdoors? I wonder what the effects of wrapping that with Reflectix might have on your effluent…theory being if that ductwork is cooling your exhaust, perhaps there may be some benefit in retaining some of the heat until it exits into the outdoors?

Interesting thought John. That pipe traverses an unused extra bedroom that has little need for environment modification. In fact, due the the extreme insulation (even the insulation is insulated) we installed when we renovated this 70 year old house to the studs, it require little A/C or heat to meet the temperature levels required. This is a problem when attempting to have the A/C reduce humidity as it doesnt run long enough. Hence the dehumidification system and control logic work. If we were as smart when we renovated as we are now, we would have inisisted on a lower capacity A/C unit which would have run longer. On the other hand, our energy bills are very low.

I can now respond to the question of taste influence of lower roast room humidity by saying that in a blind taste test coffee roasted at the new lower humidity (and -for me- much faster time) has been judged beter than previous batches. Can’t quantify “how much better” other than to repeat this comment “wow, what is this?” "It tastes great!


Bob Werby Today 10/26 I just completed 3 back to back runs of Kenya beans at a charge of 1,250grams (1.25KG) using the new door handle weighting. I had no issues with the door pushing open. All runs were to my call of City+ at close to 2 minutes after start of first crack. The end dump times were 11:39, 11:12, and 11:56 for the three runs. Once again validating that the Bullet is at the very least a 1KG under 12 minute machine. My Power was 119.9 volts to 120.2 volts at socket during the roast. Environmental was 42% RH with a 21°C Temp.

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Oh man…

Preparing for a week in the mountains with friends I did a big roast night before last. 60-something degrees in San Francisco and 99.99% humidity.

What a mistake.

Three good roasts and then the machine lost its mind. Control panel pushing its own buttons, exhaust coming out of new places. The roaster went through PRS PRS PRS PRS with fans and drum and panel lighting up and turning off like it was haunted. A-02 error.

Hard to keep the fans going, the PRS button kept “pushing itself”. I assume the control panel circuit board is covered in sticky coffee syrup. And much of the machine’s insides. :frowning:

I got it into a cooling mode eventually. I dont think there was any damage. But I definitely have a big clean ahead of me.

Watch out for extreme humidity.

on the plus side, my garage smells amazing today.


Can’t beat good smelling garbage! :slight_smile:

If you did 3 roasts before things went south, the machine was warm enough you shouldn’t have had an issue with condensation. You probably need to contact Support so you can find out what the codes were and what they mean. Well- I assume there are codes since you had such odd behavior, but if you had that behavior and no codes that seems an issue in itself.


I’m in the Houston area and have been worried about roasting outside due to the high heat and humidity. If you are not having problems with overheating (due to outside temps) or with slower roasts (due to humidity) this appears to be the opposite of what the @beachbob writes above. I usually roast in a corner of my kitchen, but we keep the temp at 80 F. I added an external cooling fan for the PCB since I am so worried about overheating. Perhaps I don’t need to be.


I finally opened it all up and did a deep clean. Because it had been “pushing its own buttons” I figured I should look behind the control panel. No issues there, very clean. Was worried there might be stickyness.

Plenty to clean in the chaff collector and exhaust area. But not much more than usual.

Probably my metal chaff filter was clogged (though it didn’t seem so to me at the time).