Re: Temperature Problems

[nikosgi]

i will oblige with adding to the confusion.
Although I use a dimmer (hi-tech from IKEA) to add control to the air intake beyond the damper, I follow the below approach (assuming pre-heating has been done):
1.charge depending on the bean and what I am aiming for between 180 and 200 C
2.at that point I reduce heat almost to zero (as edtbjon advised 0.25KPa allows u to effectively do this and avoid the hassle of having to reignite when, in the beginning of ur roasting education at least, you want to concentrate on other things)
3.i have been experimenting w slow, 'intrinsic' drying phases where I do not add heat until the beans have gone trough the turn and reached 125-135C or apply power aggressively at 3.5KPa straight when the beans turn  around 100C - so far I prefer the latter approach in terms of taste
4.At this point I open the air damper fully and turn my dimmer to half-way, so lets assume it corresponds to having a half-open damper.
5.I approach FC I turn air full on and lower heat, as I want to exit FC w almost no power but full air for a flattish development phase. This is the most delicate and idiosyncratic part of the roast for me and I am still not 100pc happy. I tend to lower to 1.5KPa and lower at about 180C, .75KPa at 200C.
6.When FC is in progress I often go to .25KPa (or turn heat off completely but leaving it on helps just in case I need it and can't afford to waste time to reignite).
7. I push the lever to de-perforate my drum, turn air to max and achieve a flat parallel development phase, targeting 15-25% dev time.
8. In extreme cases when I find heat rising more than I like it I even open the top (bean drop) damper a bit to put some cool air inside..shocking i know

My issue currently is how can I arrest the temp rise during FC so it does not go over 205C, as my roasts get to 214-220. Although pleasant to drink, w nice body etc, they are more 'feel-good' coffees and hide the characteristics I would expect from some of the more delicate greens; in other words I have trouble w last roasts..

In any case, some of these steps might help u control the huge better and not confuse you further!

[edtbjon]

I took the liberty to split this message from the original thread, as it deals with different though similar problems. Most obvious is that you're on a perforated setup while the original thread is about a solid drum setup.

Now to your problems. In short about your current issue, i.e. arresting the temp rise during FC, is to start taking the heat down a bit earlier. It's not good practice to fully step on the brakes (full air and no heat...) if you can prevent it by being lighter on the gas earlier on during the roast.
One thing that I've noticed with the T setup is that the bean drop damper does leak a bit, making the exhaust fan less effective. Because of this I'm currently take off the funnel and put a sealing hat on top of the roaster trying to seal it a bit better. Opening that damper will not draw out heat from the roaster, as the easiest air flow path becomes outside air going through the damper to the exhaust fan...

[peshewacoffee]

I took the liberty to split this message from the original thread, as it deals with different though similar problems. Most obvious is that you're on a perforated setup while the original thread is about a solid drum setup.

Now to your problems. In short about your current issue, i.e. arresting the temp rise during FC, is to start taking the heat down a bit earlier. It's not good practice to fully step on the brakes (full air and no heat...) if you can prevent it by being lighter on the gas earlier on during the roast.
One thing that I've noticed with the T setup is that the bean drop damper does leak a bit, making the exhaust fan less effective. Because of this I'm currently take off the funnel and put a sealing hat on top of the roaster trying to seal it a bit better. Opening that damper will not draw out heat from the roaster, as the easiest air flow path becomes outside air going through the damper to the exhaust fan...

I pretty much assumed what you are describing but didn't take the steps to correct it. What do you use to seal the top?

[nikosgi]

thanks edtbjon. I have been lowering heat a few minutes before the FC start but will experiment further. I am not turning off heat on FC to be clear, the process has started well in advance. The challenge in implementing this now will be to find the sweet spot of starting the lowering and defining the increments thereof. Practice makes perfect.

Interesting point on the top damper and the cap you use and what you say makes sense. I have been observing a drop in ET when I do that though.

More roasts for me now to see if I can get a light enough Ethiopian..

[edtbjon]

Yes, it's all about learning how the roaster reacts at different stages of the roast. I've roasted with my Huky for two years now and I'm still learning something in every session.
From what most perf.drum users report, the area where the perf.drum really shines is with light roasts. As always it's just that "small" matter of perfecting the roaster control pattern.
About the leakage in the top damper... I don't think that the ET dropping because of the exhaust system being more efficient is a bad thing, but because that efficiency now draws more heat out of the roaster you have to make a small adjustment on your "swedish" fan controller will take care of that. (I "saw" (listened to) a recent video by "N3roaster" on roaster control, where he talks about opening the charge chute as a "last measurement" means of controlling the roaster in a small segment of the roast. While he roasts on a huge Diedrich or Probat, the effect is just about the same, apart from that the leakage is constant on the top of the Huky...)

[easygene]

Edtbjon says:

"One thing that I've noticed with the T setup is that the bean drop damper does leak a bit, making the exhaust fan less effective. Because of this I'm currently take off the funnel and put a sealing hat on top of the roaster trying to seal it a bit better."

Good idea.  Do you use some type of small metal cap?

This is an extremely interesting topic and I appreciate Edtbjon's splitting it off.
I'm a low heat and no fan at charge disciple of Edtbjon's and currently still leaving damper closed experimenting.  Have had some really tasty roasts.  Of course had some really tasty roasts with perf open from time to time as well.  Trying to solidify an opinion as to which is best is too elusive it seems at the moment.
One thing, the last of my Peterson Farms Gesha will be roasted for New Years using open perf and closing just before 1C as that seems to appeal to my taste buds from experience and aiming for C to C+.

Thank you Nikosgi and Edtbjon and hope to hear from others especially those shooting for light roasts which the perf seems to excel at and which comprises most of my roasts.  Trying to get a handle on temperature problems can consume my day.  But oh so much fun.

[nikosgi]

I thought of coming back to this thread and add a couple of profiles for different approaches on Ethiopian Yirga and some initial tasting notes. Both roasts were on 325g on same day.

roast 1 - NG_Ethiopia_16 (messed up during export as I found out, w events missing; I added some times manually)

A slowish roast. Temperature run off a bit peaking at 215 and rising constantly, albeit at different deltas, until DROP.

This did not help the bean and as expected produced a rather darker than required roast. While still on the light side, colourwise, the beans demonstrated the occasional oil sweat when I put them to an informal cupping after a 5d rest.

Development was probably a bit too protracted, but that is something I would need further experimentation on.

Aroma had hints of fruit that I would expect from the bean, but not so pronounced. This painted a picture that was reaffirmed during tasting. Taste was rather muddled, though by no means unpleasant. It would not hit the mark for Ethiopia. The mouthfeel was acceptable, viscous enough and pleasant. Aftertaste was again nothing to write home about. Again, the coffee is very drinkable, but not what I wanted to get out of the bean. It was confined to a cold brew w some spices added to lift it up.

roast 1 - NG_Ethiopia_17

A faster roast than previously, though longish in its own right. Temp was much better controlled this time with a peak almost 10C lower at 206, which was nearly exactly what I was after (maybe 1-2C lower). The delta was again as I had planned it beforehand. As I sealed this for resting I had high expectations.

These were only partially satisfied. It was a lightish roast, very close to colour to an outside professionally-roasted 'control Ethiopian batch'. Aroma was definitely fruity and promising. Interestingly the coffee did not hold the crust during cupping, though it may be a process issue. Tasting left me ambivalent. The brightness is very clear if not a bit too pronounced. Where I wanted some more balance, and I hoped to achieve this w the longish development, I didn't quite get it..I didn't get the desired sugar to balance the brightness, leaving this a rather one-sided Ethiopian.

A day after the cupping, an Aeropress brew produced a pleasant but rather 'light' in feel coffee. It would be for example a better cup if i blended some darker roasted Brasil or similar..

The puzzle I want to solve now, and I need your help if you could assist(!), is to get this roundness for light roasts. I see the following areas I can explore:

1. shorten the overall time as it seems to be rather long for Huky, from others I have seen. To this end have a quicker rise after TP and do not develop for so long (cut at least 1.5 - 2' there). Allow higher than the 206C top temps but for very little time.

2. keep the same profile as in 17 and just shorten the development by 1.5-2.

Of the two, I would think 1 should work better, as I can't see how 2 would produce anth better..Any ideas before I go back to roasting appreciated!

[nikosgi]

seem to have issues attaching..