I’m curious to see if anyone is interested in sharing what they have found is the best use for the fan.
On a recent trip to a coffee farm I was introduced to an experienced roaster, grader and producer. I made the most of the opportunity and asked all of the questions I could recall that have been tumbling around my head for the last couple of months. One of the main ones being what is the fan for and how/when should it be used?
In the name of honesty I am still grappling with his answer, and have yet to fully digest it, but this is what he said… more or less.
He explained that the fan removes pressure from the roast, and that depending on the situation, it is necesary to release pressure from the roasting chamber. This explanation was tied into a larger conversation about a specific farm that produces particularly small and dense beans that take a lot of heat upfront but then seem to develp too quickly after yellowing.
He continued on saying that you want enough pressure to break down the outside cellular structure of the bean, allowing the heat to penetrate deeper but you don’t want to let the heat over cook the outside leaving the inside under developed. Somehow the fan plays into this, it allows the inside to continued developing as you release the burden from the outside.
On another note he mentioned that you likely don’t want to blast your fan all at once, but rather ease into higher fan speeds. He mad an analogy about holding onto a rope while leaning back, how there is pressure on the rope and if it is released slowly you will have time to adjust your weight to stay balanced, however if the ropes tension is released all at once you will be jerked back and fall, meaning your roast will crash.
It’s incredible the amount of knowledge some people have amassed, and I feel particularly lucky to be able to meet such incredible people that are so willing to pass on what they know. I will be talking more on my experience in the future but for now I am curious to hear about what people on here think about the subject of using your fan during the roast.
Best Regards to all
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Hi!
I agree that pressure is an important part of how airflow affects the roast. To me, however, airflow management is mainly about adjusting the balance between origin character and roast character rather than deciding that one approach is always better than another.
In practice, this includes determining the highest fan setting appropriate for each batch and knowing how to coordinate power reduction with increased airflow toward the end of the roast. These decisions depend on the coffee, the batch size, how the roast is progressing, and what you want the coffee to express in the cup.
Best regards
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That’s something I’m interesting in developing, the ability to measure where the fan can be used and to what degree. I like how you frame it as a way to control origin flavors and roastyness. I currently have some very dense very small beans that need a lot of energy upfront but tend to run away after yellowing. I believe the fan can help me balance that out and avoid tipping, scorching and even burning them.
What coffee has been your most challenging to roast and did the fan help you achieve a great result?
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Good morning / good afternoon,
I used to be most afraid of roasting Ethiopian naturals, but these days I actually find washed coffees more challenging.
For me, one of the hardest parts is managing moisture correctly. If too much moisture remains, I often get more vegetal and bitter notes. But if too much moisture is removed too early, I find it becomes harder to carry heat evenly into the inner layers of the bean.
Of course, you can compensate by extending the roast, but in my experience, pushing the roast too long can also flatten the character of the coffee.
So yes, the fan helps a lot. I use airflow as one of the main tools to manage how moisture is removed through the different layers of the bean.
Best regards,
Jerome
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I really doubt this guy was referring to “air pressure”.
He was probably using the term “pressure” to refer to the temperature gradient or heat energy at the surface of the bean relative to that at the bean core.
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@cafe.natureve
Thank you for describing it so well, I have been posing the question every experiened roaster willing to answer, your response might be the one that stikes the closest to the root of what the fan is for. I have a lot to learn and hone in, but during the process I will be thinking about moisture more.
Right now I’m learning to roast naturals better, I have my washed coffee ( Huila Santa Maria ) honed in pretty well, but I have a handful of naturals that I am even hesitant to approach haha. Do you progressively introduce the fan after yellowing or how do you apply it?
@gabyritaseek.qiAO
I believe it is both, seeing as high pressure translates to both heat and psi. That’s why if you quickly empy a spray can it will feel cold. If you think of a drum getting hotter and hotter and it being a closed environment relative to the outside, the air pressure inside the drum will in fact be higher. But in practical terms yes the idea is that pressure or heat allows the roaster to develop the inside of the coffee bean.
How long have you been roasting and how did you end up here amongst the home and micro batch roasters?
Hi!
I generally increase the fan progressively as the roast goes on. One reason is that the amount of smoke and gases also increases later in the roast — if you have ever roasted outdoors, you can see this quite clearly.
But I don’t necessarily start increasing the fan after yellowing. I prefer to respond to how the RoR is developing and work with the natural progression of the roast. I believe the RoR should be allowed to decline naturally, regardless of the plan we made before the roast.
I’ve written a few articles about RoR. If you search for “RoR In The Aillio Bullet R1 / R2: How To Read IBTS And Bean Probe,” you should be able to find one of them.
Cheers!
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I’ve used the same curve, naturally declinig. I try not to use too many adjustments, but I will start to experiment with the fan, especially later on in the roast.
Your article is very in depth, it actually answered some questions I didn’t know how to ask yet. I know how the ibts works and how the bean probe works. What I was still trying to understand was why should I pay attention to the “delayed” bean probe. It’s all about moisture and a handful of other factors that contribute to what the bean probe tells you. I’ll be going back to that article as a reference without a doubt. I also appreciate you pointing things out on roast curves and explaining the reasoning behind it, there is so much nuance in roasting!
Thank you for all the information!
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