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Thread: Help with dip in ROR just after first crack

  1. #1
    Senior Member Lukemc's Avatar
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    Help with dip in ROR just after first crack

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    I'm aiming for a slowly declining ROR throughout my roasts but always get a dip just after 1st crack starts. It rebounds after but wondering why this is.

    I'm roasting on a 1kg gas roaster. Charging 1.2kg and am happy with the results but can't remember why this happens. I'm sure is been discussed somewhere on here before but can't find it!

  2. #2
    Mal Dimal's Avatar
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    G'day Luke...

    All to do with pyrolysis at this stage of the roast mate.
    Rather than go on with a wordy explanation here, it is quite well explained on the Coffee Research website. Here's a link...
    Coffee Roasting - CoffeeResearch.org

    Mal.
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  3. #3
    Senior Member Lukemc's Avatar
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    Thanks Mal shall have a read
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  4. #4
    Life-long Learner DesigningByCoffee's Avatar
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    Hi Luke
    FWIW I began roasting thinking I should always drop temp just before first crack, say 195 measured, to stop the roast running away – but like you I always got the dip. I think it's because, as the articles may say, when the beans are 'cracking' they actually are throwing out a heap of energy in the process - so need a bit extra to balance this up and keep the temps rising.
    From playing around over a little while now, I have figured out that with my setup (750g batches) that pushing the higher temp a little further into first crack before reducing, I can remove the dip. So I now keep temp on until 203 (with FC beginning about 200) and then drop a bit of input temp every 5 from there to the end of the roast.
    Here's a recent profile - you'll see where and what I drop in the red at the bottom…

    Hope that might help!
    Matt

    20170321-MochaJava22amb.jpg
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  5. #5
    Senior Member Lukemc's Avatar
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    Thanks Matt.

    The only way I can get rid of the dip with my roaster at present is to keep up the heat as you said but also increase airflow a fair bit during first crack. Then lower heat and airflow once first crack has finished to try to stop the roast running away!!!

    Always learning.

    Thanks for the reply
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  6. #6
    Life-long Learner DesigningByCoffee's Avatar
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    Yep - it is a delicate balance at that end of the proceedings!

  7. #7
    Senior Member coffeechris's Avatar
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    Hey Luke, have you done any roasts under 1kg? if so what are the results? I take it your charging at 1.2 as you are looking to yield 1kg at the end.
    Cheers,

    Chris

  8. #8
    Senior Member Lukemc's Avatar
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    Behmor Coffee Roaster
    Yeah that's it Chris. Good question. I'll give that a try soon and see how it reacts..... I actually have a bunch of profiles from the previous owner who charged 900gms. I'll have a look how his ROR went too.



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