Chaff not evacuating

Hey all,
Roasts getting a little better. Longer periods to yellow, shorter malliard’s, appropriate finishes. It takes a little hoop-jumping to make it happen as the machine really has some intrinsic behavior quirks.

I’ve noticed a lot of chaff around the beans say from near yellow to drop. Don’t have this same situation with other roaster.

I run fan from F2>F3>F4 during roast but it doesn’t seem to evacuate. Wondering if the amount of chaff burning around the beans early in the roast is leading to offputting flavors. I know that the chaff is getting pretty dark when the beans are just going to yellow.

Just wanted to see what level of chaff you all had around your beans at different phases of the roast.


After my latest round of roasting I too found the chaff not sufficiently clearing, and this was using the same stepped (calibrated) fan settings as you, F2-F3-F4. When I would drop it into the cooling the tray, the white filter would quickly become completely covered by a thick layer of chaff essentially preventing my beans from cooling in a timely manner. I actually pulled the bowl out with the hot beans still in it and vacuumed the filter quickly to resume cooling. Not something I want to do every time!

Perhaps 10 seconds before dropping cranking the fan to F6 or F7 could help? Anyone else do this?

I have stirred the beans with a spatula while holding a shop vac hose to suck the chaff out of the beans while they were in the cooling bowl.

I don’t think that’s how its supposed to be though.

As posted elsewhere, I’m going to try more fan earlier to get the chaff out quicker, maybe ending in the 6-7 range at drop.

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There are 2 fans that affect chaff movement-

  • the exhaust fan and
  • the fan located down low and to the rear of the drum.

That 2nd fan provides air flow to the drum and to the power board. I would think if that rear fan were not working right you would be getting overheating errors, but it is part of the exhaust air flow.


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Thanks Bruce.

Both fans are working and I’m not having any overheating issues.

I think I will just have to find a way to run F over 4 to evacuate burnt chaff from the roasting beans without sucking out too much heat.

Kicking it up to F6/F7 during the end might help to clear chaff from the roast so it doesn’t end up in the cooling tray.

I’m more concerned about what’s happening to my flavors when I’m watching beautiful yellow to very light brown beans swimming through a sea of burnt, black chaff from Malliard forward.

Black chaff appearing early in the roast is a little unusual. I’ve only seen this once, from beans that were strangely processed with some kind of honey method. Those required very low preheat and low power early in the roast to avoid burning the chaff, combined with higher fan (F4 with 325g batch size) to evacuate most of the (heavy) chaff as soon as it was produced. This obviously leads to long roast times. I never did achieve a great roast of that bean, but did at least eliminate the charred flavors in the cup. Hope this is an unusual case for you to, and your next batches of green beans aren’t so challenging. BTW, what is your preheat temp and batch size?

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Both preheat temp and batch size are varying as I try to learn this machine. When its too low the roasts end up flat-tasting as there isn’t enough energy early in the roast so the middle stretches out too long.

The chaff has been present across all processing methods including washed.

Yes sure more or less chaff from all bean types, but black charred chaff around Yellow point seems weird. I’ve had good luck with preheat temperatures around 200C for batch sizes 325g - 500g, total roast times around 8-12 minutes. Are your roasts in this range? Maybe post a link to a typical roast that has the black chaff problem?

The most likely comment will be too high a charge temp, which maybe on-point for this soft and large Pacamara. But it was also present in two recent Tanzania roasts which are smaller, harder, higher elevation washed beans

Hey Brian… I’m with Brad here on the PH temp. I looked at the link you posted. I feel for a 500g batch 500F / 260C is too hot. Like Brad when I roast 500g my PH is in the 392F / 200C range Brad is talking about. Sometimes I go to 401F / 205C and sometime the 1 setting below 200C.

I roasted a Tanzania 1kg batch with a high PH of 590F / 310C and I didn’t have an issue with black chaff - that was an experiment as I normally would use 572C / 300C for 1kg.

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With these low charge temps and 500G charges how long are your other phases?

Do you have enough energy so Malliard is shorter than the time to yellow? Is this a reasonable scenario with the Bullet?

My best roasts over the years have historically been 45-55% to yellow, 35-40% Malliard, and 15%-25% "development).

I think it matters.

Feel free to hop over to RW and look at my 1 lb or 500g roasts. Mine is typically 45-48% / 28-30% / 20-22%. I think it depends on how you control P and F (and probably D as well) after you charge the beans as well. I’m no expert, but my friends that I roast for are happy :slight_smile: