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Roasting slow-fast profile in the KKTO

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  • #46
    Hi ArnhemR - it's not suited to the KKTO, you're right, but alas I own a KKTO and it's coffee is not suited to my tastes! So I'm seeing what I can do to modify the design or approach to make it do what I want. One day I'll fail in this pursuit and get a more suitable roaster for my liking :P But in the meantime I'm a student, living in an apartment, with no income of my own so... this is the extent to which my wife will let me go. All I want is those delicious fruity flavours that I know exist in my (especially African) greens. But maybe I'll have to stick to nuttiness and cocoa.

    My turbo oven already has (almost) as much control of it as I can wield. I can already control it's power level (albeit through pulsing rather than PWM) from always on through to always off. Rather than let it go full boar, I usually use my PID to set a maximum environment temperature. This isn't ideal, as really I should have the thing on full boar most of the time, and have some way of controlling the airflow to manipulate my environment temps. Corretto owners do this with lids on their bread pans, KKTO owners like yourself typically do it with burping. I found that KKTO approach too difficult to repeat but maybe I should give it another shot.

    I'm well aware that my thermocouples will behave uniquely - most of the concern about TCs in this thread is that they have drifted, so what value they have had recently is diminishing - until I fix the problem. Whether I like it or not, TCs are my best guide with my KKTO. With a small bean mass and a large amount of mechanical noise (don't know about you, but my Turbo Oven has got to the stage of rattling and requires retightening regularly) 1C isn't very discernable, and telling steam and smoke apart with such a sealed system is difficult.

    Most of the people I have read that are happy with KKTOs are, like yourself, much further north than I am. Makes me wonder whether there is a distinct advantage for the KKTO user in a warmer ambient climate. I had much less finicky roasts in summer (Again well aware that all roasters require adjustments for winter conditions).

    On the design front, I would posit that a solution would be to actually build in an exhaust (with fan). Either a tube straight down from false floor through the base, or diagonally from false floor to wall of roaster - which will draw the warm convective air across the beans with much more velocity, pull out chaff, draw out steam and smoke and make airflow a controllable dimension of the roast without more mods to my Turbo Oven. Then I could have the turbo oven always on. But the idea of more Stainless Steel drilling is not at all appealing, and further engineering decisions like diameter of tubes would make it a risky move. Still - I might do that some time as an experiment.

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    • #47
      fair points readeral, you are aiming for the opposite flavour profile to my preference so i dont have anything to offer you there!

      I am surprised you cant hear FC clearly - thats never been an issue with my KKTO

      I sort of get the feeling though that you are complicating the process somewhat, I have never felt that controlling the air low was necessary, although I did experiment with a speed controller on the fan but found I couldnt detect any difference.

      I do think bigger batches are easier to control on the KKTO, I would suggest you try the biggest batch that makes sense with your usage. If you can roast as much as 600g green, aiming for 500g roasted (roughly), then I would try preheating to around 180deg and drop in the beans and leave on full heat until just before FC, start burping to slow the BT RoR to around 5 deg/m and finish when you like the look of the beans. Alternatively control the RoR approaching FC by turning the thermostat right down.

      What software are you using to record profiles?

      I would be surprised if it were not possible to roast on the KKTO to suit your flavour profile without major mods.

      Its worth hitting up Paul (the inventor of the KKTO ) for his thoughts, he is always happy to share his vast knowledge and experience.

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      • #48
        Originally posted by readeral View Post
        Couple this with the likely evaporative cooling due to poor exhaust/air flow, and we've got ourselves a complex problem.

        I'm sure I've got some science wrong - feel free to correct me, but in the context of solving this problem of effectively executing a slow-fast profile in a KKTO.
        I'll return to the rest of you post a bit later when not on my phone, but I just wanted to ask - where the evaporative cooling concerns have come from? i.e. what do you think is going on, and why do you think it is of particular concern in your roaster?

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        • #49
          Hello again Al...

          An Aussie source of some really good info about coffee roasting comes from highly respected Roaster Extraordinaire Anne Cooper, who currently has been running a series of articles in the Cafe Culture Magazine. All of their articles can be read online or the magazine can be subscribed.

          Anyway, thought that this episode might have some information of interest for you, starting on page #32...
          https://issuu.com/cafeculture/docs/c...22766/37516812

          Mal.

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          • #50
            Excellent, thanks Mal. Glad she's been writing - a mate of mine went on some workshops with her and thought she was brilliant (I actually have a copy of that equilibrium graph on my PC - but not with her heat transfer details). Alas, a lot of what he took away (beyond this excellent kind of content), was specific to his Has Garanti.

            It's good to read the distinction of natural and forced convection, and how it needs to carry the bulk of the roast. Gives me confidence in the lower charge temps, but also my need for improved convection.

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            • #51
              Originally posted by MrJack View Post
              I'll return to the rest of you post a bit later when not on my phone, but I just wanted to ask - where the evaporative cooling concerns have come from? i.e. what do you think is going on, and why do you think it is of particular concern in your roaster?
              Well, Steve mentioned it up in number 12, but I've read up about it with regards to 'the stall' when slow-cooking meat, and that's assisted by increasing airflow. I'm creating a humid environment which is stopping moisture being taken from the bean surface, and so getting in the way of my heat transfer. I think. Possibly. My post says "likely". Again, I'm not particularly hung up on this being 'the thing', it's just (possibly!) a factor, and will probably fix itself with other changes.

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              • #52
                Originally posted by ArnhemR View Post
                fair points readeral, you are aiming for the opposite flavour profile to my preference so i dont have anything to offer you there!

                I am surprised you cant hear FC clearly - thats never been an issue with my KKTO

                I sort of get the feeling though that you are complicating the process somewhat, I have never felt that controlling the air low was necessary, although I did experiment with a speed controller on the fan but found I couldnt detect any difference.

                I do think bigger batches are easier to control on the KKTO, I would suggest you try the biggest batch that makes sense with your usage. If you can roast as much as 600g green, aiming for 500g roasted (roughly), then I would try preheating to around 180deg and drop in the beans and leave on full heat until just before FC, start burping to slow the BT RoR to around 5 deg/m and finish when you like the look of the beans. Alternatively control the RoR approaching FC by turning the thermostat right down.

                What software are you using to record profiles?

                I would be surprised if it were not possible to roast on the KKTO to suit your flavour profile without major mods.

                Its worth hitting up Paul (the inventor of the KKTO ) for his thoughts, he is always happy to share his vast knowledge and experience.
                It depends on the beans. Some are clear, some are impossible. I work hard to make sure I can hear it, but my thermocouples are a good indicator of when I should be listening out and if it should have finished.

                I'll have a crack at your 600g 180 degree preheat and full on for the rest of the roast suggestion with some of these african beans. That's close to what I did when I first built the KKTO for my first few months of roasting in it, and is similar to my approach for softer beans - but keeping an eye on the upper temperatures of the system.

                I'm using Artisan to record my profiles - prior to that I was using RoastLogger, which I actually preferred, but I have an Arduino with a TC4 as my logger and controller of element, and at the time I was rigging it all together Artisan was going to be more straight-forward. Now they're much for muchness, and I might move back to RoastLogger at some point. It has much better smoothing, and doesn't poll the Arduino for data points, but takes all the raw data and processes it itself.

                Paul and I have had a number of conversations over the past 12 months, mostly in terms of build, but some in terms of roasting approach. A lot of our conversations have been documented elsewhere on this forum. The 'set and forget' might be great for most, but what I'm really after is to be able to manipulate my roast, control the 3 phases of the roast to enhance or suppress bean characteristics, much like Matt and Mal do with their Corretto setups. It could just be that the KKTO isn't agile enough for it, but I'm giving it a go! I like a lot of the KKTO package, but I'm not convinced there isn't an opportunity for improvements (a la my experiments in the past). It's just a question of whether I have the time, tools and tenacity to do it.

                I'd love to be able to hit my preferred flavour profile with a simple approach - but over the past 12 months, it hasn't yet come up the goods.

                I probably sound really ungrateful for the conversation and advice - I'm not, I do appreciate all of the input everyone is putting in. It would just be exhausting to outline everything that I've tried in my roaster thus far, and all of the conversations I've had on and offline with various people.

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