espressojr wrote:... this is my general approach to using airflow:
-During the last minute or so of drying (around 270F), I turn on the fan to 25% to remove humidity.
-I keep the fan at 25% through development until right before FC (around 360F) when I turn it up to 80% to remove smoke.
I'm still not sure how the fans works in relationship to temp as I usually turn down the heat at this point to 50%.

Jim, based on hundreds of HT roasts, my best pulls result from roasts that reach FC in about 10-11 minutes, and use a high load temperature. To maximize roasting energy in the underpowered HT, consider keeping the fan OFF before FC. The fan plays its most strategic role after FC begins; then you will use the fan to expel smoke, to tame the smoldering beans, and to develop the roast over several minutes.

Turning the fan ON around 270F does nothing to enhance espresso flavor and punch.

Fern

Sorry I am about a month late into this discussion. I too am trying to figure out how to manipulate airflow on my hottop B2K, particularly with SM Ethiopia dry process Aricha. I have been following the new roasting guidelines for the B2K according to HottopUSA and have been getting great results when roasting wet processed coffees. However, this dry process Ethiopian is giving me trouble. Just for a point of reference, I have not yet installed a BMT and am just taking readings from the hottop display for now.

I use 227g, dropped into the drum at 350, at about 5:00 min (320f) I increase fan speed to 25% (heat is still at 100%), at 350f I turn the heat down to 80% and fan up to 50%. I get the first pop of first crack at 9:00min (376f). as first crack begins to roll, I continue to decrease heat and increase the fan until I am at 100% fan, and 30% heat. First crack generally ends 1:45-2 minutes later (11min total time) (402f) I would like to drop the beans at about 30 seconds after first crack to get a nice city roast. However, first crack REALLY seems to take off when I bring the fan up to 100%, and even roasts that were stopped at 400f still seem to have a bit too much roast taste for my liking. It would seem that the increase in fan speed resulted in an increase in convection, which is why the temperature rises so quickly. Has anybody had success with not increasing fan speed during first crack, and instead, just lowering the heat. Again, I know a lot of these temperature readings are askew and difficult to interpret because I have not yet installed a bean mass probe.

The single most important mod on a Hottop remains the installation of a BMT probe.
Great Hottop Modifications

What you are experiencing may be related to the exothermic nature of the roast during 1C. You should be able to compensate for this by lowering heat further, and increasing fan speed sooner.

Fern

ciel-007 wrote:The single most important mod on a Hottop remains the installation of a BMT probe.

+1

boulderbrew wrote:It would seem that the increase in fan speed resulted in an increase in convection, which is why the temperature rises so quickly. Has anybody had success with not increasing fan speed during first crack, and instead, just lowering the heat. Again, I know a lot of these temperature readings are askew and difficult to interpret because I have not yet installed a bean mass probe.

I normally follow a similar profile as you do, but I do have installed thermocouples for both ET and BT. I don't normally increase fan speed at first crack.

Here is my roast of the SM Ethiopia dry process Aricha. I did not like my shortest roast with this coffee:
Ethiopia DP Gr. 1 Yirga Cheffe Aricha-Current crop at Sweet Maria's

boulderbrew wrote:It would seem that the increase in fan speed resulted in an increase in convection, which is why the temperature rises so quickly. Has anybody had success with not increasing fan speed during first crack, and instead, just lowering the heat.

I'm a hottop user. I have had "success" not varying the fan during the entire roast. But what do you mean by success? do you trust my own judgement of my own roasting?
So for my last two entries to the roasting competitions on this board, I only lowered the heat for first cracks, without varying the fan at that stage of roasting. I read somewhere else that one reason for the common practice of turning up the fan during first cracks is to pull the chaff out the drum. But for the Hottop, chaff management is a joke at any fan level. So I figure there's no other reason to turn up the fan for first cracks on the Hottop. To me it's just another variable to work with that I really dont need, and I like to simplify things. Higher convection gives you more even heat through the drum, and you lose moisture, and on the Hottop you lose some aromatics because the air escapes through the back. You already achieve even heat distribution from lowering heat input (still maintaining stable ET). As long as you have sufficient airflow like you do during the entire roast leading up to first cracks, I dont see why one needs to increase it during first cracks, especially on the Hottop. I used to turn up the fan at first cracks a while back, but I remember that either I couldnt tell the difference in the cup or I preferred one with constant fan through first cracks.

Adding larger veins in the drum also makes a noticeable difference. Like many others my roaster has gone through several upgrades. It has roasted enough coffee that my original heating element actually warped/sagged from all the heat cycles. Looked like a pretzel when I took it out and replaced it. I also scrapped the rear filter long ago.

I usually run 100% heat during the drying phase with no fan. Then as I get 3/4 through drying I turn the fan on at 25%. The added air flow accelerates the bean temperature rise. As I hit the first pops of first I ramp the fan up to 75% and cut the heat to around 15-20%. About half way thought first I will twiddle with the fan and heat based on the bean mass thermocouple to stay in the butter zone for the profile I am after. As I near the end of first I drop the fan to around 50% and increase the heat to keep the momentum going until I hit my end point. I also heat the drum to 350F before I drop my greens in which is far past the HotTop ready beep. Beyond that, practice.

Every bean is different and every roast is different. Changes in the humidity and ambient temperature will effect the roast day to day so you have to watch your numbers and adjust the heat/fan accordingly.

thanks for the input guys. It really seems like many of my questions could be answered by installing a BMT in conjunction with a roast profile documentation type program. I am hesitant to tear the hottop down to install the probes in the back wall...I wonder if going through the bean chute will work for now, although it seems that the bean chute method yields slightly less accurate results than an insulated probe through the back wall. Since my last post, I have experimented with two different profiles (still using 350f drop temp, charging 227g). The first revolves around using a higher fan speed (50-75%) after drying phase. I have noticed an increase ROR when I use the fan (odd because many users observe the exact opposite), so this method gives allows me to get a quicker FC. The second method (same initial parameters) involves keeping the fan at 25% right at the end of the drying phase, and keeping the fan speed there throughout the roast. I only vary the heating element power here and begin to drop power around one minute pre FC. So far I have preferred the second profile that uses a constant fan speed. Is there any truth to the idea that using more airflow will strip more moisture from the beans, and in turn strip some nuanced notes? I feel like I had read somewhere before that using more airflow in a drum roaster actually accentuated some nuanced flavors. Sorry I am so long winded, just trying to get a firm grasp on hottop roasting, I have been thoroughly enjoying my roasts, I just know there is always room to grow!

I do believe that higher fan speed would give you more clarity in flavors, and a shorter, dryer finish in the cup, up to a certain point. It all depends on your roast profile, your total roast duration, and how much moisture is left going into first cracks. It also depends on your development time past beginning of first cracks until drop. For me personally I never turn the Hottop fan higher than 50%. Tyipcally I use 25% until end of drying, then turn up to 50% for remainder of the roast, with all the caveats stated above plus few I have missed. It all comes down to your final cup, and your personal preference. So now you have 2 data points. You may further optimize by turning the knob, with the knob being at what BT you turn up your fan from 25%, while trying to keep everything else being equal. You may find something better than your previous 2 cups.

Happy roasting and cupping