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Thread: 1kG Roasting process

  1. #1
    Senior Member brettreaby's Avatar
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    1kG Roasting process

    after having the gas 1kg roaster for around 18 months and around 150 roasts I have got the process down to a few steps i thought i would share. lately, i have mounted 3 timers to remind me of the steps

    control panel w timers.jpg

    I do have roast monitor with flue temp and bean temp, but now i dont worry about the graph, i just keep an eye on bean temp and rate of temp rise of bean temp.

    the process:

    1. i only ever roast 1kg of beans ( keeps my variables under control)

    gas p warm up.jpg

    2. with roaster at 210C [ usually for 30 minutes ], dump beans
    2a: airflow and drum speed 30%, gas set at ~1.5 kpa ( about 2/3 of open gas tap power?)

    roast gas p.jpg

    3. turn OFF gas for 1min30 secs ( to allow bean readout to drop to around 80C)
    4. turn ON gas at 1.30 mark.
    5. at 6 min mark ( the approx time drying of beans completes and colour changes from greenish to light brown:
    turn down gas to 0.7 kpa, turn UP airflow and rotation to 50% [ i.e. reduce heating input during caramelization phase]
    6. at 9.30min mark start observing colour via sampler)
    7. at 10 min start cooling fan and drum, drops some sampled beans to check colour
    8. continue dumping samples until desired result (which i base on colour)
    9. dump beans, reset settings to 2a and get ready for 2nd roast. Usual duration is 10-11 minutes first roast.

    i usually do about 3 kg and find the roast time decreases as i progress by say 30 seconds each roast.

    With the above process i am getting excellent and repeatable results.

    m roaster is a chinese knock off of the millcityroaster [ i would say from the same factory] an delighted with it.

    Hope this helps anyone as a starting point, interested in others process variations to this?
    Andy, coffeechris, fg1972 and 3 others like this.

  2. #2
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    Just to let you on know on a slight technicality with the comments above.

    In Point #5..........when you turn up airflow and rotation speed on a drum roaster, it's not actually reducing heating input - it's instantly increasing thermal exchange with the coffee and it can have a remarkable or significant immediate effect.

    Obviously, the result from an earlier action turning down the heat source (your gas) will ultimately result in a reduction of heat at a later point in the cycle, but the increased air speed and rotational velocity of the drum will have transferred greater units of heat into the beans.

    Of course, whatever works for you is fine and the comments I make above are not meant to suggest you change what you are doing.

  3. #3
    CoffeeSnobs Owner Andy's Avatar
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    Quote Originally Posted by medalbandit View Post
    ...
    when you turn up airflow and rotation speed on a drum roaster, it's not actually reducing heating input
    Blanket statements like the above on forums can mislead people when they are regurgitated as indisputable fact.

    On many drum roasters adding extra air will reduce the heat quickly (particularly at this time of year with a cold ambient intake). It really depends on your roaster design, where it pulls the air from and how much stored/residual energy is available in the drum. It's easy enough to see the effect with thermocouples at each end of the drum.

    What's most important is that the owner learns what works best on their particular setup in their particular environment.

    With the above process i am getting excellent and repeatable results.
    Great post Brett, I'm sure that will really help someone who is struggling to get a baseline on a new roaster.

  4. #4
    Senior Member brettreaby's Avatar
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    Behmor Coffee Roaster
    at step 5 [ 6 minutes] all 3 changes are together : gas down, drum and airflow up so the heat input is indeed reduced and thermal transfer increased. Not sure your point?



    Quote Originally Posted by medalbandit View Post
    Just to let you on know on a slight technicality with the comments above.

    In Point #5..........when you turn up airflow and rotation speed on a drum roaster, it's not actually reducing heating input - it's instantly increasing thermal exchange with the coffee and it can have a remarkable or significant immediate effect.

    Obviously, the result from an earlier action turning down the heat source (your gas) will ultimately result in a reduction of heat at a later point in the cycle, but the increased air speed and rotational velocity of the drum will have transferred greater units of heat into the beans.

    Of course, whatever works for you is fine and the comments I make above are not meant to suggest you change what you are doing.

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