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First roast with corretto + PNG Wahgi

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  • dan110024
    replied
    It turns out that the unstable RoR temps are put down to hot exhaust air being drawn back into the gun.

    I've started roasting in the driveway instead of the garage on nice days and the gusts of wind are overcoming the fan I use to blow the air away.

    So you two were right

    I would have thought the Bosch digital heat gun would have had a closed loop system too. I'm wondering if it can't react fast enough when a gust of hot air gets blown across the intake.

    Looks like I'll keep the roasting to the garage from now on.

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  • Dimal
    replied
    What about the new Bosch 2300W Heatgun Dan...

    Unless you're doing batches of 1.0Kg plus on a continuous basis, I doubt that you would ever come close to stretching the limits of control with 2.3KW at your disposal...

    By way of an example, I only use ~1.3KW to control a batch size of 650g in my Corretto setup, so still have a further 700W up my sleeve if I needed to go to larger batches for some reason. Maybe there is a problem with your particular Heatgun too mate, as other CSers who use the same HG as yours have never reported this issue, that I am aware of at least...

    I use a "Makita HG6020 2000W Heat Gun", mainly because it uses a 'Closed Loop' control system to maintain an accurate output temperature. Control is facilitated with the use of an Heat Output dial that's graduated from 1-10. Not as granular as the control on the Bosch but nevertheless is accurate and repeatable.

    Mal.
    Last edited by Dimal; 28 October 2015, 12:03 AM.

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  • dan110024
    replied
    I do have a miniature fan which points at the heatgun. It is a possibility that variances in heat are affecting the output temperature. I really needed an environment temp probe to see what the output temperatures really were.

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  • sidewayss
    replied
    With regards to the heatgun, the heat from the breadmaker may cause the erratic behaviour which may cause the readings on the gun to drop and then catch up when there,s clear air.
    I normally run a fan on low speed which assists in blowing the chaff which would otherwise find its way into the heatgun and the heat/smoke away from the coretto as well as the roasting station.

    Attached pic is my roasting station which demands a fan for reliability.

    If you need more info about roasting, Coffeeshrub (roasting fundamentals) via Sweet Maria,s may help.Click image for larger version

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  • dan110024
    replied
    She died! After 54 roasts the motor in the bread maker gave up and doesn't want to play ball. I don't blame it with the amount of chaff and heat that passed over/through it.

    I have a bunch of improvements I'd like to make to the next roaster. Things like somehow sealing off the gap between the bowl and the bread maker. Too much heat was lost through the gaps and made cleaning out the chaff a pain. There is also an annoying issue of the Bosch electronic heat gun, where it will slightly adjust the fan speed if it's got trouble maintaining or reaching temperature (I'm assuming that's what it's doing when I hear the slight changes in fan speed). This could be the cause to the stochastic nature of the RoR at some points where it should be cruising along just fine. I'm no longer confident that I have 100% of the capacity control using this particular heat gun, especially in cold ambient conditions where it may struggle.

    I've been thinking about buying a 2000w heating element and hobbiest 50mm ducted fan and having complete control over the two. I'd then be able to experiment with arduino. Not an automated roasting system, but something I can control easily enough myself. It just depends how long I want to go having to put up with supermarket grade coffee.

    Anyway...this corretto served me well! A few great batches, a few not so great, but mostly better than typical supermarket coffee which was the aim all along.
    Last edited by dan110024; 26 October 2015, 07:57 PM.

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  • dan110024
    replied
    Thanks Mal!

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  • Dimal
    replied
    G'day Dan...

    There are a few very good websites containing useful information about roasting coffee. A couple of the ones I refer to from time to time are...
    Coffee Roasting - CoffeeResearch.org , and
    Willem Boot Coffee Articles - PDF Downloads... https://bootcoffee.com/resources/

    Lots of great information to keep you interested...

    Mal.

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  • dan110024
    replied
    A bit of a random question... And I know I could probably find out through research, but I keep forgetting and I'm feeling a little lazy right now

    What causes the RoR to drop when rolling through first crack? Does it have anything to do with the beans letting off steam and letting latent heat go through evaporation? I'm wondering this because when you try to compensate with more heat, the RoR can easily get away from you once the drop finishes.

    And on the note of further reading... Can either of you guys recommend good roasting literature/books? I curated all the relevant blog posts from sweetmarias but found it was very poorly written and edited (some good information though).

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  • dan110024
    replied
    I have decided to start logging my roasts in Excel to gather a little more information and eventually log the data of experiments with different RoR's through different phases of the roast. While RoastMonitor is easy to use and displays the fundamental information, I was wanting a little more out of it.

    I made a small table that I can copy/paste into the spreadsheets that RoastMonitor spits out (I work with a separate copy to which RoastMonitor uses, to not disturb the original). I think I've included all the information you're able to gather from the data generated. I'd love to hear if there is anything else I've missed that may be useful.

    Click image for larger version

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    The only input the table requires (the orange cells, which match the other colour once filled) is the bean mass, ambient temperature and bean temperature (before roast). The rest is generated from the data within the spreadsheet that RoastMonitor has generated.

    I'm 99% confident that the table works on pretty much every roast it's pasted into. One variable I had to work around was the row count. Obviously longer roasts have more rows. To overcome this, I made the formulas read down 5000 rows (a 19 minute roast is around 1200 rows, so it should be safe).

    Something else that may be off is the load/preheat temperature. It's taking the temperature at which the load button was pressed. Obviously if you have a lid on your corretto, and lift it to drop the beans, and THEN press the button, the load temperature will read lower than what you had preheated to. I'm going to start pressing the button at the time I lift the lid so I can combat this error. Or you could just manually move the Load cell to the point where the temperature starts to drop (like I have for my current sheets)...but that means manual work which this is trying to avoid.

    The 'load turning point' temperature has to be less than 50°C for the value to work (it looks for a value less than 50 to find where the turning point is marked). I still don't have much experience with roasting, but I would say that the turning point is always below 50°C, right?

    Depending on where you unloaded the roast (before or after second crack), some cells will blank themselves out. For example, if you unload before second crack, the 'First crack to second crack' and 'second crack to unload' will not display a value. It looked a little confusing and messy if I left them displayed.


    TL;DR?/Too long; didn't read?
    Paste the table into a copy of the roast spreadsheet, manually fill in the cells that are orange (they will match the colours of the rest once they have data in them), and voila... You have all the data you want (unless someone tells me otherwise)!


    I'm hosting the file on my Google Drive account... I think it should work for whoever wants it. I'll probably forget about it and it will sit there until Google go bankrupt/forever.

    https://docs.google.com/uc?id=0B_Xr5...xport=download

    Leave a comment:


  • DesigningByCoffee
    replied
    Originally posted by Dimal View Post
    Dan...

    Don't know that you would need to stretch out your batch times much more than this though - roughly 20 minutes for the last batch.

    It really is very important to ensure that the bean mass is being agitated evenly throughout so that the thermal energy input is being as evenly distributed as possible. This will obviate the need to stretch out roast times too much as you then run the risk of flattening out the flavour profile, which is not always a desirable outcome.

    Mal.
    Yeah sorry - that was my oversight
    I did mean to say that the profile looked pretty good, despite being longer than your baseline … end up going on with the general principles

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  • Dimal
    replied
    Originally posted by DesigningByCoffee View Post
    You'll probably find that you'll need to stretch out your roasts a little longer with the bigger batches to achieve a similar flavour profile
    Dan...

    Don't know that you would need to stretch out your batch times much more than this though - roughly 20 minutes for the last batch.

    It really is very important to ensure that the bean mass is being agitated evenly throughout so that the thermal energy input is being as evenly distributed as possible. This will obviate the need to stretch out roast times too much as you then run the risk of flattening out the flavour profile, which is not always a desirable outcome.

    Mal.

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  • Dimal
    replied
    Originally posted by dan110024 View Post
    I think my sieve is too fine for some of the chaff. A lot of it seems to just sit in the bottom. Is there any particular reason why the coolers I see draw air down through the beans? Is it so the chaff doesn't go flying out everywhere?
    Yes mate, that's one part of the equation...

    Also, drawing air through a moving mass of beans (or anything similar) ensures that the beans are being cooled substantially evenly throughout the mass. Trying to push air through such a mass does not result in the same evenly distributed cooling effect, as a significant volume of air is deflected away. That's basically it in a nutshell....

    Mal.

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  • dan110024
    replied
    On the occasion I lifted the lid to check the pan was sitting correctly, I did see the top wasn't moving all that much. The colour of the beans seem to look consistent, but I don't know if that's much of an indicator. I might look at modifying the paddle if I go down the road of 750g batches.

    Will keep an eye (tongue?) out for the sourness.

    Leave a comment:


  • DesigningByCoffee
    replied
    You'll probably find that you'll need to stretch out your roasts a little longer with the bigger batches to achieve a similar flavour profile - I certainly did. When I matched the shorter RoR of a smaller batch - the results were always sour. Possibly has something to do with the lag in building up an ideal thermal mass in the beans - just takes longer.
    Also check that the beans are mixing evenly, especially later in the roast as they expand - sometimes the larger batches end up like the proverbial swan - serene on top and paddling like crazy underneath! That's when I ended up going to an extended paddle…
    Also, if you are struggling with getting good times - then pre-heating higher can help. I never used to preheat with 350g batches, but with 750g preheating to 120° or so took 2-3 mins off the time but allowed for the same gun input temps - reducing the risk of scorching

    But yes - the results are much smoother and less responsive in the profile.

    Let us know how it tastes!
    Matt

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  • dan110024
    replied
    I think my sieve is too fine for some of the chaff. A lot of it seems to just sit in the bottom. Is there any particular reason why the coolers I see draw air down through the beans? Is it so the chaff doesn't go flying out everywhere?

    I had ~300g of PNG Wahgi left over which wasn't enough to roast in the corretto, so I decided to add it to the last 500g of the Peru CDS. This made the batch size a little over 800g. Really pushed the corretto to the limit!! I now see how the gun temperatures have to be so much greater to get the same RoR. A much more stable temperature increase in a batch of this size, compared to 500g.

    The profile isn't aligned too well with the template I was using, but I ended up getting the RoR to the desired 11 deg/min which followed the template well enough. I tried going for a darker roast this time as the others have been a bit light for milk based drinks. I didn't have much of an idea of what I was doing and ended up dumping it around 50 seconds after second crack.

    With a total of 864 grams (green), the corretto handled it damn well. I need to make up a bracket to stop the pan lifting up due to the extra resistance against the paddle. I could hear it jumping up every so often at the beginning. It eventually calmed down half way into the roast once the beans lost some mass I guess. The extra power of the bean cooler definitely helped in this case...I could barely move the beans around in the sieve without them overflowing. I think a 750g batch will be just right.

    Peru CDS - 62%
    PNG Wahgi - 38%

    Can't wait to see how it is in the cup. Got about a week worth of Peru CDS to get through before this will go in.

    Click image for larger version

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    Last edited by dan110024; 27 May 2015, 02:36 PM.

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