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Thread: Slowing down the roast

  1. #1
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    Slowing down the roast

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Im roasting in Perth using a popper.

    In these cold months I find if I roast outside, using a 25m extension cord, I can get a roast out to 6.5 - 8 minutes (stopping at second crack). Results are ok. The 25m extension cords adds roughly 1-2 minutes to roast time.

    Has anyone come up with any simple ways to extend popper roast time (ie not taking machine apart to modify)?

    I interested in what people in Perth do in summer - I initially tried home roasting in summer and my roasts were awful, gave up and only started again this week. Given the conditions Im roasting in now I just cant see that I can home roast in summer and get acceptable results.

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    Re: Slowing down the roast

    Do you use a chimmney? How much coffee do you put in? I can roast a cup of coffee each time.

    Surely in summer you could use a fan? or AC?

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    CoffeeSnobs Owner Andy's Avatar
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    Re: Slowing down the roast

    Pop next to a bucket of ice?

    Apart from the VERY obvious water and electricity issues....

    the popper sucks all the air that it heats from the base...
    the cooler that air is the longer your roast will take.

    It might be as easy as sitting a couple of trays of ice-cubes beside your popper when you roast?

    ....unless you are good friends with your local butcher and can use his walk-in cool-room for popping coffee. ;D

    Your next step would be the heatgun I expect. Then you can control the amount of heat applied.

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    Super Moderator Javaphile's Avatar
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    Re: Slowing down the roast

    Chimney would get my vote to try first.

    Java "I need more beans Scotty! I must have more beans!" phile

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    Re: Slowing down the roast

    AlMac,

    Try the chimney as suggested. I have and it definitely works. I have found that the roast time can go up to 10-12 minutes to 2nd crack with some beans on the really cold days. This is roasting about 100 to 120 G of beans.

    Cheers,

    Louis

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    Re: Slowing down the roast

    Thanks everyone.

    What do people use for a chimney?


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    Re: Slowing down the roast

    Ive seen tin cans, wire mesh and those glass bits from kerosene lamps.

    -Stephen-

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    Re: Slowing down the roast

    The easiest chimmney is a tin can, that has been washed and both ends cut out. Then you just need to tie it on to the popper. it also makes a great funnel to pour the beans out

    Mal uses a hurricane lantern glass, which is a great idea and cost about $12


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    Re: Slowing down the roast

    Perfect.

    Has anyone done a chimney study?

    Does height of the chimney affect roast time? Does a longer chimney = slower roast or vice versa?

    Simliarly does a fat chimney (like the can) slow the roast while a thin one may speed it up (or vice versa)?

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    Re: Slowing down the roast

    Hmm,
    I dont know, you might have to check a.c. or you could give it a try ;)

  11. #11
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    Re: Slowing down the roast

    Almac,
    Some roasters use an adjustable transformer called a "Variac" but they are not exactly cheap! You can get them from Jaycar but from memory they are about $399.
    You might also want to try a couple of different brands of poppers to see if some are slower. Most of the budget stores (like the Warehouse) sell a version for about $20.
    Alternatively, you could try another roasting method such as a heatgun where you have control over the distance from the beans.
    There are quite a number of CS members who have very refined heatgun methods/systems.
    Have a browse through the threads in the "roaster" section.
    Also well worth perusing the links found here:

    http://www.homeroaster.com/homemade.html

    Ahhhhhh roasting brings out the Gyro Gearloose in all of us.


    :D

  12. #12
    Super Moderator Javaphile's Avatar
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    Re: Slowing down the roast

    Quote Originally Posted by AlMac link=1118894468/0#8 date=1118916484
    Perfect.

    Has anyone done a chimney study?

    Does height of the chimney affect roast time? Does a longer chimney = slower roast or vice versa?

    Simliarly does a fat chimney (like the can) slow the roast while a thin one may speed it up (or vice versa)?
    Chimney height does not affect roast times except as it allows you to add more beans.

    The diameter of your chimney should be narrow enough that there are no dead air spaces around the bottom where the chimney meets the popper, and wide enough that there is no air leakage around its base. Beyond that I dont know that the diameter of the chimney will affect the roast much.

    Chimneys in and of themselves do not change the roasting profile of your popper. Chimneys are used to extend the height of the roasting chamber which then allows you to roast more beans per batch. It is the larger bean mass that slows down your roast, not the chimney itself.

    Java "Go, go gadget roaster!" phile

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    Re: Slowing down the roast

    Snippet from Javaphile:
    The diameter of your chimney should be narrow enough that there are no dead air spaces around the bottom where the chimney meets the popper, and wide enough that there is no air leakage around its base. Beyond that I dont know that the diameter of the chimney will affect the roast much.
    The only thing Ive discovered with using chimneys, is that you need to make sure that the exhaust hole diameter of the chimney is the same size or larger than the diameter of the top of the popper roasting chamber. Smaller than this diameter is a bad thing because it tends to "choke" the popper and roasting temperatures can rise quite sharply to the detriment of both the coffee and the popper. Found this out the hard way :-[.

    Cheers,
    Mal.

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    Re: Slowing down the roast

    Quote Originally Posted by Mal link=1118894468/0#12 date=1119013746
    The only thing Ive discovered with using chimneys, is that you need to make sure that the exhaust hole diameter of the chimney is the same size or larger than the diameter of the top of the popper roasting chamber. Smaller than this diameter is a bad thing because it tends to "choke" the popper and roasting temperatures can rise quite sharply to the detriment of both the coffee and the popper. Found this out the hard way :-[.

    Cheers,Mal.
    Makes sense to me. :D

    Java "Gotta love experimenting!" phile

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    Re: Slowing down the roast

    Roasted with the Chimney last night in the popper (old cocoa tin - perfect width and reasonable bit higher than a normal tin can). Dropped the bean weight down to 100g. Worked a treat and lengthened roast out by around 3-4 minutes total (wasnt watching the clock so close).

    Thanks Everyone.

  16. #16
    Super Moderator Javaphile's Avatar
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    Re: Slowing down the roast

    Usually people add beans when using a chimney to lengthen the roast time.

    Java "Questioning look" phile

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    Re: Slowing down the roast

    Quote Originally Posted by Javaphile link=1118894468/15#15 date=1119194527
    Usually people add beans when using a chimney to lengthen the roast time.

    Java "Questioning look" phile
    Opinion seems to be split on this with some saying less beans = longer roast and others saying more beans = longer roast time. It seemed to me that less beans roasted both longer and more evenly, although it may be that 100g green is the max that my popper can handel, so constitutes the more beans. Will have to experiment.

    How high to people fill the popper with chimney - eg to the top of the roasting chamber in the popper?

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    Re: Slowing down the roast

    It depends on the size/height of the chimmney. I use a Tin can and put a cup of beans in, otherwise they start getting chucked out the top.

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    Re: Slowing down the roast

    Hi All,

    Regarding controlling Roast Temp in a popper, you definitely have to ADD beans to INCREASE the Roast Temp, and REMOVE beans to DECREASE the Roast Temp.

    This info was gathered via experiment using a Fluke DMM with K type Thermocouple, with the t/c bead situated so that it was roughly half-way up the bean roasting column. Increased temperature translates to shorter roast times and visa-versa.

    Eventually you reach a point where the Fluid Bed collapses due to overloading the roast batch size. Obviously you need to stop adding beans well before this point to avoid burning both your beans and melting your popper. Hope this helps,

    Cheers,
    Mal.

  20. #20
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    Re: Slowing down the roast

    Ive worked out a fool proof way to slow the roast: shelve the popper and buy a heat gun.

  21. #21
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    Re: Slowing down the roast

    Uhh Yeah,

    Great solution but what about those of us who cant use a Heat Gun or any other hand held device? In my situation for example, after a series of strokes I have very limited strength and dexterity in my left arm and hand, and about a third left in my right. Makes trying to wield a Heat Gun or similar very difficult....

    Cheers,
    Mal.

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    Re: Slowing down the roast

    Just tie the heatgun up with some string so its hanging over the beans. I suspend mine between the bbq and the balcony railing. That way you can adjust the roast timing by varying the distance the gun is from the beans (by removing heat pads from under the colander).

  23. #23
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    Re: Slowing down the roast

    Hmmm,

    Still doesnt sound as easy as using my popper. Just plug it in, pour in the beans, turn it on, turn it off, pour beans into fan cooler. Im not too good at trying to tie things up with string and getting the angle of the dangle, just so.

    My ultimate aim is to build a modified Stir Crazy/Turbo Oven roaster so that I can reduce the number of roast batches that I currently do. In the end, I guess we all use a method that works best for each individuals situation. The $50 ALDI Turbo Oven has me very interested at the moment.

    Cheers,
    Mal.

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    Re: Slowing down the roast

    They have them at coles to for $59???

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    Re: Slowing down the roast

    Mal

    The most I could stretch my popper out to was 7 minutes, outside with 100g of beans on a 7 deg night. Summer is a no-go zone with my popper. If you could get your popper over 7 minutes regularly then the heat gun is probably not an issue - unless you need to roast a lot of coffee and are time poor. With all these issues the heat gun was a saviour for me.

    If I could get the stir crazy turbo thing happening then thatd be even better but my mother in law wont give me her turbo with glass lid.

  26. #26
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    Re: Slowing down the roast

    Quote Originally Posted by AlMac link=1118894468/15#24 date=1120184210
    If I could get the stir crazy turbo thing happening then thatd be even better but my mother in law wont give me her turbo with glass lid.
    Ohhh,

    What a spoiled sport. Cant you bribe her with promises of unbelievably great coffee? Or is she a non-imbiber?

    Re: my popper... I have made a small mod that allows me to control the fan speed and therefore the roast size and duration. We probably only go through about 280-400 grams of coffee per week, depending on visitors and relies, etc so the popper is well up to the job being asked of it at this stage.

    Cant help thinking that a good SC/TO roaster would be a considerable step up though.... now where did I put my tinkering cap, got so many of the damn things these days I keep losing em. All the best,

    Mal.

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    Re: Slowing down the roast

    I have had the same experience. I can tell you that there arent many solutions. A popper in a warm environment will need serious modification to the way it ventilates and allows air to the element and really modification to the thermostat.
    For a cheap popper none of ths is feasable.
    If you have a good quality popper like the poppery, you can do it but all the cheap stuff is just too crappy. If you dont mind sacrificing your popper then it would be worth trying to mod it, there are plenty of web sites out there that willtell you how.
    Sorry to bring you bad news but its not a brick wall, dont give up.
    Sacrifice your popper to science and play around with it.
    Cheers...
    Bruce...

  28. #28
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    Re: Slowing down the roast

    Quote Originally Posted by Bruce link=1118894468/15#26 date=1120286092
    I have had the same experience. I can tell you that there arent many solutions. A popper in a warm environment will need serious modification to the way it ventilates and allows air to the element and really modification to the thermostat.
    For a cheap popper none of ths is feasable.
    Cheers...
    Bruce...
    Hi Bruce,

    I spose it all comes down to what you call a serious mod and what you interpret as feasible. Ive got two Mistral poppers and at $17.00 each, I guess they would have to fall in to the "cheap" category.

    In order to improve the amount of air being transported through the roasting chamber, I have made two relatively simple mods (one on each popper) that differ slightly from each other but achieve more or less the same outcome. I would always recommend that anyone contemplating a modification to an Electrical Appliance, should enlist the assistance of a friendly local licensed electrician. Its not that the mods are complex but its better to be safe than sorry where 240 Volts is concerned.

    The simplest of the two mods involved a procedure to reduce the resistance of the Fan Motor Dropping Resistor and thereby increase the Voltage to the Motor.... more Voltage equates to more speed. This mod took about 30 minutes to complete using only basic tools and materials.

    The second mod went a bit further in that a Fan Motor Speed Control was devised and fitted. A little more complex than the first but not overly so. This involved the use of more materials and components, and therefore cost too but in all, everything was purchased for less than $20.00 all up and took about 2 Hours to complete... still not excessive in my opinion.

    As things turned out, I didnt have to touch the t/stats or the fusible link and left these "as is" and in circuit to provide a level of over temperature protection. Using a Fluke DMM with a Fluke K type t/couple temperature probe, I measured the temp in the roasting chamber of each popper during a roast, about midway of the vertical column of beans.

    The popper with the basic mod starts off at around 195 C once the fluid bed is established and ramps up slowly to about 218 C before the onset of 2nd Crack. The popper with the variable speed fan is a lot more flexible in that I can roast larger batches, stretch the roast out or contract it, basically whatever I want within the limits of the fans safe operating limits. Currently, this is set to a maximum of 20% above the nominal Fan Motor Voltage of 25 Volts D.C. which so far, hasnt been to the detriment of the Fan or Motor. In practice, I have never had to exceed 10-12% above nominal applied voltage in order to stretch roast batches of 120 grams out to 12-13 minutes in the middle of Summer.

    Since I dont have an Air Flow-meter, it is impossible therefore to accurately estimate the actual volumes of air being transported through the popper but at plus 10%, the increase in air flow is very noticeable as an increase in force against my hand. I suppose I could rig up a water column Manometer and measure the changes in Static Air Pressure but even for me, this would probably be going a bit too far. It is after all, only intended as a basic mod to allow me to derive a basic level of control over my roasts for the least amount of expense, in terms of both money and effort.

    So, for my money, the "cheap" popper is definitely the way to go. Why risk damaging a more expensive unit, even without the mods, to the extra hardship of roasting coffee? Regarding feasibility of such an undertaking. I believe it is entirely feasible providing the usual precautions are taken when playing with the innards of a 240 Volt appliance. Theres bound to be a Sparky not too far away from most Roasters who would be only too happy to help out when some top quality coffee may be offered in return.

    I guess when you come right down to it, yes, I am a tinkerer but so are a great many CS members. Its kind of a second nature to most of us and for those less imbued with this kind of enthusiasm, there are enough keen members out there to help others out when and if the opportunities arise and practicalities allow. I sure dont mind helping out wherever I can. Anyway, time for bed so, all the best and

    Cheers,
    Mal.

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    Re: Slowing down the roast

    Quote Originally Posted by Mal link=1118894468/15#25 date=1120273331

    Ohhh,

    What a spoiled sport. Cant you bribe her with promises of unbelievably great coffee? Or is she a non-imbiber?
    Already did that - she no longer drinks Nescaf - just flat whites at our house.

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    Re: Slowing down the roast

    My "cheap" solution to Variac is to use 2 dimmers set up in parallel.
    Since my popper is rated at 1200W, and the dimmer are 600W, putting them in parallel distributes the load.
    But that means, you have to adjust the knobs together. To aid that, i mounted my two dimmers on a box side by side and wrapped a big rubber band across the two knobs.
    With the separate fan control it works really great!
    Kai Seng

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    Re: Slowing down the roast

    Sounds interesting lkaiseng. Can you tell us about your roasts. Any chance of some pictures?

    Cheers,

    Louis

  32. #32
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    Re: Slowing down the roast

    Hi all, I was wondering how this would go in slowing the roasting process down.
    Splitting the popper into two circuits, fan and heater, as Mal has done, leaving the fan connected to the main on/off switch so that it is running whenever the unit is switched on, but having the heater on a separately installed switch so that it could be cycled on and off during the roast. The heater could be cycled say 1 or 2 seconds every 10, depeding on the profile of your popper.
    Its not exactly scientific, but it might help to gain a bit more control over the heating.
    All the best,
    Steve.

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    Re: Slowing down the roast

    Hi louis, here my popper pics
    http://sg.pg.photos.yahoo.com/ph/ope...80.jpg&.src=ph

    My working bean mass is currently about 120g (going for more, so juz configured it for an untested higher fan voltage).
    For heat dimmer, at 30% setting, it gives me a slow ramp to 130 Celsuis in 6-7mins. From then on, 10% more pushes it pass first crack and second crack by the 8-9 min. (overlapping cracks, so trying different heat and fan settings for this stage). So about 5% of the beans are a bit too dark/oily spots.
    Cappuccino tasted fine this morning (after a day rest), truer test when i do an espresso later.

    Cheers!!

  34. #34
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    Re: Slowing down the roast

    Hmmm,

    I would be a bit worried about the possibility of the two controllers getting slightly out of sync. For the Heating Element, you could build a simple Triac Output controller that could handle the full load on its own, very cheaply.

    Lovey,

    I havent really bothered with going any further than controlling the fan speed because for my needs, 100-120 gram batches are quite enough most of the time. Only time it would be handy to have more capacity is for when I roast batches as gifts for birthdays, Xmas, etc. Since I usually make these about 500 grams, 4-5 roasts per household at Xmas can wear a bit thin by the time I get about half-way through the list. But hey, Xmas is Xmas :).

    How easy it is to split the Fan and Heater circuits depends a lot on the brand of popper you have. Some of them are remarkably easy to do and even have an A.C. Fan Motor which makes it even easier. The cheaper you go though, the more difficult it seems to become as the manufacturers try to cram as much as possible into the smallest possible space. You end up with both 240 Volts A.C. and 25 Volts D.C. on the same little Printed Circuit Board that is soldered to the Fan Motor connection tags. Makes it quite difficult to end up with an elegant solution for splitting up the supplies.

    Makes all of this very interesting to say the least. All the best,

    Mal.

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    Re: Slowing down the roast

    Ok guys.
    We need some diagrams here ;D
    Cheers...
    Bruce...

  36. #36
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    Re: Slowing down the roast

    My "cheap" solution to Variac is to use 2 dimmers set up in parallel.
    Since my popper is rated at 1200W, and the dimmer are 600W, putting them in parallel distributes the load.
    Very nice solution Kai Seng...
    and with the addition of a plug and a socket this could be used for many different projects.

    hmmm....... ;)

  37. #37
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    Re: Slowing down the roast

    Quote Originally Posted by Bruce link=1118894468/30#34 date=1120559452
    Ok guys.
    We need some diagrams here ;D
    Cheers...
    Bruce...
    Hi Bruce,

    Lots of info about this and much more can be found here... http://www.homeroaster.com/homemade.html.

    Cheers,
    Mal.

  38. #38
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    Re: Slowing down the roast

    Hmm, my popper is taking less than 2 minutes 45 secs to first crack and 5 minutes to the second crack. If I go much longer than that, the beans end up very dark, oily and bitter.

    And those roasts were done outside (for the cool air and to dispel the chaff) and on a couple of extension leads.

    I may have to increase the air flow or reduce the heat. Ive got a Variac so Ill try that first.

    Ron

  39. #39
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    Re: Slowing down the roast

    Behmor Coffee Roaster
    Those times equate to mine. Ive read much about using extensioin leads to increase the resistance and therefore get a lower voltage.... But I suspect thats usually the case in the US where electricity supply isnt as good as ours.

    I constantly stir the beans with a long-handled wooden spoon so that they get a more even roast.



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