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#231: Post by **drgary** » August 27th, 2023, 5:10 pm

Yes, Hoos wrote recently that he now automatically sets the fan to its highest setting. He has experience with every kind of roaster, used a fluid bed during a class I attended, was a Loring consultant, and uses a USRC 3Kg sometimes, including for sample roasting. Anyway, my first try with a Kenya washed coffee at 100% fan settings is quite tasty. When mentioning the high fan settings Hoos made the point that this wouldn't dry out the coffee.

To me, drying the bean during the roast suggests heating it unevenly or alternatively baking it. Whether the heat is applied via IR, conduction from hot metal or convection, it's still heat penetrating a dense seed.

Long ago, I tried a Hoos technique* to use the fan speed that most efficiently delivered heat to the coffee. It ended up dried and undrinkable, but I believe that was because I was delivering too much heat to the beans faster than they could roast evenly, especially now that I'm more experienced with my drum roaster.

But I don't want to take this discussion too far off topic rather than focus on the IKAWA.

* This involved finding a fan setting with the highest power that would reach first crack the fastest. On my machine, that was 60% fan. Perhaps a much lower heat setting at 60% fan would work well enough.

#232: Post by **GDM528** » August 27th, 2023, 5:21 pm

"Fluid Bed" is a pretty high bar, thermodynamically speaking. The higher the airflow, the higher the heat input to maintain temperature. I imagine a 1Kg scaled-up version of the IKAWA would require a dedicated 220V 50A circuit to power it.

Lowering the airflow increases the thermal gradient in the roast. I measured over 20C just from the airflow in my long-gone FreshRoast. And since this is an IKAWA thread: kudos to them for engineering a system that creates such a uniform thermal environment around the greens.

I'm curious why there aren't more prosumer fluid beds that recycle the air. Does the coffee taste worse when the roast soaks in its own gasses?

#233: Post by **Erichimedes** » August 27th, 2023, 5:34 pm

drgary wrote: Also, I amskeptical about heavy moisture in the environment affecting the moisture content of the coffee, considering that you are applying so much heat at the inlet of an air roaster that you would drive away water vapor from the air.

Not quite, if the air entering the roaster has a certain amount of moisture in it, then the air exiting will have the same amount, regardless of how much it raises in temp. When roasting it will leave with even more, since the beans are losing water.

Hotter air actually has a greater capacity for carrying water:
https://www.engineeringtoolbox.com/maxi ... _1403.html

I'm not totally convinced that fluid beds dry faster, it's just a hunch. Also whether it has anything at all to do with humidity level is actually a separate hypothesis anyway.

I just see more % moisture loss than I expect on a lot of beans, like a 17.1% loss on a Columbia that only saw the first couple snaps of second crack. But like I said, just a hunch.

#234: Post by **GDM528** » August 27th, 2023, 5:38 pm

drgary wrote:Long ago, I tried a Hoos technique* to use the fan speed that most efficiently delivered heat to the coffee. It ended up dried and undrinkable, but I believe that was because I was delivering too much heat to the beans faster than they could roast evenly, especially now that I'm more experienced with my drum roaster.

I'm wondering if this is an explorable territory (at least for me) with the IKAWA. I've been getting lots of positive feedback for RoR profiles that start with a big jump in the first 30 seconds to 170C inlet temperature. There some Pro model profiles that pre-heat even higher than that. The IKAWA is so good at pinning the exterior temperature of the bean, I can focus on how I want that temperature to interact with the water inside.

Typical stovetop preparations for caramelizing sugar can take 20 minutes, so I get a little freaked out when I see sub-5min Pro profiles. On a drum roaster, are light roast profiles - prior to first crack - typically longer or shorter than dark roast profiles?

#235: Post by **Erichimedes** » August 27th, 2023, 5:39 pm

GDM528 wrote:From the moisture readings I'm taking now, it looks like I may never completely dry the greens. But looking at the difference between inlet temperature and BT, it appears the beans are tracking the inlet 1:1 after about 2-3 minutes. Beyond that point the remaining moisture may be inconsequential in cooling the beans, so maybe that qualifies as 'dry'.

Some illustrative examples:
IKAWA Home - profiles
IKAWA inlet profile calculator

Sorry, I meant the colloquially referred to range of ambient to about 300 degrees F that roasters call the "drying phase"

August 27th, 2023, 5:54 pm

Cool, got it!
So, in that context, I've been trying to cross the 300F mark within the first minute of the roast, like, asap. It's fast enough that I look at other aspects of the roast (like inlet/BT tracking) to estimate when the loose water is actually gone, which is closer to 2min. It's just some weird jag I'm on with using the water to 'steam' the greens as they caramelize, hoping to create more complex flavors - all theory, minimal science.

#237: Post by **Jonk** » August 27th, 2023, 6:21 pm

GDM528 wrote:Does the coffee taste worse when the roast soaks in its own gasses?

Yes, smoky in a bad way. The recirculated air needs filtering/purifying/mixing.

August 27th, 2023, 11:00 pm

GDM528 wrote:Cool, got it!
So, in that context, I've been trying to cross the 300F mark within the first minute of the roast, like, asap. It's fast enough that I look at other aspects of the roast (like inlet/BT tracking) to estimate when the loose water is actually gone, which is closer to 2min. It's just some weird jag I'm on with using the water to 'steam' the greens as they caramelize, hoping to create more complex flavors - all theory, minimal science.

Nice, good to know! I'm going to start experimenting with faster dry times. In my minimal testing, even just shortening time to yellow by 40 seconds can have a noticeable affect on weight loss, even when roasting to the same level.

GDM528 wrote: I'm curious why there aren't more prosumer fluid beds that recycle the air. Does the coffee taste worse when the roast soaks in its own gasses?

I think It's significantly harder to engineer. My second roaster recirculated about 1/3 of its exhaust and it led to all kinds of problems. There aren't good off-the-shelf options for blowers that can handle 500F air, controlling the mix of exhaust to fresh air is tricky and gas heat is really more ideal because the exhaust coats electric elements shortening their life, and you need an in-line cyclone to catch the particles.

I kind of doubt the exhaust imparts bad flavors, or the folks using Lorings would be in trouble. All they use is a cyclone. They even incinerate the chaff in-line.

#239: Post by **Jonk** » August 28th, 2023, 3:22 am

Erichimedes wrote:I kind of doubt the exhaust imparts bad flavors, or the folks using Lorings would be in trouble. All they use is a cyclone. They even incinerate the chaff in-line.

I have tried roasting in a sealed chamber. The results were awful. Loring purify the air inside the cyclone before it's recirculated:

#240: Post by **Erichimedes** » August 28th, 2023, 8:04 am

If you want to call the output of an incinerator "purified", then yes, certainly. But no actual separation of exhaust gasses occures.