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This is accomplished by pouring all of the contents of the chaff collector tray back into the roaster, and using fan preview to run the fan gently enough to drive only the chaff back up into the chaff collector.
If you find pouring the contents of the chaff collector to be a messy operation, you will find a canning funnel to be a great help. Here’s an example product:
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Once you start fan preview, immediately lower the batch size until the fan is slow enough to leave the beans in the roast chamber while driving the chaff into the chaff collector.
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