Hi Rick,
You mentioned taste as a defining crietria (naturally) and guatemalan beans in earlier posts.....for me, guatemalans are nicer roasted into rolling second crack....lots of ordinary roasts at lower temps....so maybe try some to say approx 227c.(bean temps)
Cheers
JL

JL, I'll give that a shot tomorrow. Today I ran a batch to Full City, what Sweet Maria's recommends, but using a "slow start / fast finish" profile. I'm just not producing anything decent with the "fast start / slow finish" that is indicated for hard beans like the Guatemalan.

JohnB, I did the blank roast experiment today and you're absolutely right; the HT sensor never "caught up" with the TC sensor. Even after pulling the thermocouple tip up to the level of the HT sensor at 400° on the TC, there was still over 90°F difference between the two.

At 300° on the thermocouple (before moving the tip up), there was a difference of 102° between the two and though there will be temperature gradients in the drum naturally, I don't think that there would be a 30% temperature difference.

In the graph below, rate of rise is calculated per 60 seconds and readings are taken every 30 seconds. The left "Y" axis is degrees fahrenheit and the right "Y" axis is rate of rise in degrees.

chang00 wrote:utilize the HotTop fan more frequently, as convection is a predominate form of heat transfer.

After re-reading this thread, I think this is an important concept that may be easily overlooked (I certainly did) for HotTop users. It might be easily overlooked because the HotTop is a drum roaster and not a fluidized bed roaster.

After that statement registered with me, I went back to the book "Espresso Coffee; The Science Of Quality", second edition, and found this on page 189 (emphasis mine):

"...the roasting process to be energetically optimized must be operated with small temperature differences and high heat transfer coefficients, meaning low temperatures and high velocities of the hot gases."

Therefore should I not be thinking of the fan as a heat sink but more as a heat source enhancer for the beans? Obviously the fan removes the hot gases from the drum, but in the process it first circulates it through the bean mass.

I leave the fan on F1 from 300*bt until just before 1C when I cut the heat & turn up the fan.

Have been roasting 250 gm. beans for past yr. with varying success. Drip coffee is not a good measure of taste as most are acceptable. espresso accentuates the taste good or bad which made me realize that there is much room for improvement.

Initially I have been dropping the beans at the end of the beep which is normally around 220 degrees which drops the temp to 170. I do use a bean probe and only follow that temp. Full power and fan at 0 on my HotTop B until 300 degrees at which time I start the fan at 1. From then on I do not adjust the fan. At 370 degrees I lower the heat to 4 . Most beans go through C1 around 386 to 395. I do not get 4 minutes from end of C1 to C2 but normally drop the beans at 420 to 430 degrees depending on the bean.

Now decided to change my profile. Drop the greens in at 220 ( Drops the temp to 170) and bring them to 250 at 5 rather than full power. At 250 I increase to full power to get the beans up to 360-365 where I reduce the power to 4. When I notice the temp ramp slowing around 3 minutes after C1 I increase the temp to 6. Have been dropping the beans a little early (420 degrees) but will try dropping them at 425. I like the taste at 420 bright and fruity but lacking body.

I like the appearance of the beans with the new profile. There is little to no scorching and they look full with well rounded edges. I believe that they retain a bit of moisture into the later stages of the roast which I believe may prevent scorching and should result in more flavour.

Will need to work more with the fan and considering dropping the bean weight to 200 - 225 to see the difference. It is taking too long to roast 250 gm I like to reast for 16-18 minutes and with the new profile I am going over 20.

Hi Rick,
Not sure the Hottop has the air flow capabilities you refer to. This is well documented in a number of discussions here and elswhere.
There are wide views on Hottop fan usage offered by experienced users, ranging from no use at all, to the one recommended in your How to Roast with Hottop notes that accompanied the roaster.

Personally, I've done post-roast cuppings using various settings with fan air on the Hottop and the consistiently best result is NO FAN during the ramps, only using fan when cooling/slowing during the 4 min roast development period from 1st to finish. (Cuping of different fan option/roasts is far from complete)

I'm right now enjoying a beautifully sweet yemen with nice after taste,(Aeropress) rested for 4 days (now 5th).

This was roasted as follows

250 grms in at 130c Hottop panel temp.

100% power.. no fan

At 155-160c BEAN TEMP, beans turning tan/orange, back bean chute off half inch for smoke/moisture to escape...NO FAN....power100%.....hardish beans will heat up at 10c per minute depending on external environment temp.

At 190c reduce power to 50%...(assuming normal external environment temp.)....open bean sute further, NO FAN.....The idea here is to go from a BEAN TEMP rate rise 0f 10c per minute down to 4-5 c per min after 1st crack.

During/immediately after first crack monitor bean temp rise....if it is still galloping, raise rear filter and apply fan 1 or 2 for 15-20 seconds to slow/stop roaster ET, as shown on Hottop panel..... BEAN TEMP will continue to rise around 4-5c per minute. Naturally you will need a timer and written log to monitor progress.

Bean temp should arrive just pre 2nd crack (218c) around 4 mins give or take a few seconds....(sometimes a short burst of fan around 212c will help if BEAN TEMP starts to race again.)

Drop beans, cup, take notes, rest for 4 days taste, more notes, and hopefully enjoy for a few more days.

Hopefully this will answer your initial question.

There are a few other considerations to the above....bean hardness for one. Indian Monsoon, as just one only example, (soft beans), require much less heat in the ramp up before !st.....Other types in between.

Also, There is the issue of attaining a higher finish temp. ie going into 2nd crack, but still maintaining 4 mins roast development time....entirely possible but may take a little practice.....simply allow more ET say 70% and use higher/longer fan to effect say a 6c-7c per min. rise....still finishing within the 4 mins. No need to go out to 5 minutes.

Hope this helps.

Cheers
JL

PS. this roast took just on 16 mins total.

Interesting to view everyone's opinions. An interesting lead in this article.

http://www.coffeed.com/viewtopic.php?f=16&t=2286

According to this study it indicates that most of the flavour develop before caramelization which is before first crack. We seem to focus almost exclusively of the time from C1 to start of C2 when the Maillard reactions take place. Albeit it is a critical time but is it to our advantage to just crank up the bean temp or should we focus on the drying cycle, and stabilization cycle pre C1?

Thanks docdvm, nice reading.
The Holy Grail of Profile, and its infinite and everchanging variables.....The second post from Brent sums it up for me.
Select a bean, roast, cup, notes, change one variable, roast again, cup etc. etc. etc.
Cheers
JL

docdvm wrote: According to this study it indicates that most of the flavour develop before caramelization which is before first crack. We seem to focus almost exclusively of the time from C1 to start of C2 when the Maillard reactions take place. Albeit it is a critical time but is it to our advantage to just crank up the bean temp or should we focus on the drying cycle, and stabilization cycle pre C1?

While the stretch from 1C to drop is important you need to be trying different charge temps, drying times & different ramp (rate of rise per minute) temps with different beans. You wouldn't roast a soft Brazil the same way you roasted a hard Central or a WP bean the same as a DP bean.

JohnB. wrote:While the stretch from 1C to drop is important you need to be trying different charge temps, drying times & different ramp (rate of rise per minute) temps with different beans.

Perfect timing on that one, John. I had an "aha moment" yesterday and discovered a problem with my drying times; they have been too short and the result was a coffee that hinted of wet basement, for lack of a better description. By changing the profile to ensure 3 - 5 minutes spent between 212° and 300°F, I eradicated that wet basement taste and am much more pleased with the end product. So I would definitely agree that the early phases are extremely important in roast profiling.

JL, now that I have my "drying phase kinks" worked out, I'll try the Guatemalan to a darker roast as you suggested.

Regarding the air flow capabilities, I've already ordered some metal air filters per JohnB's suggested modification and will be trying them as soon as they arrive (they're coming from Hong Kong...that's a long trip!). I did test the rear filter removal on my last batch and that made a huge difference in the temp's rate of rise. However, there's no direct pathway (that I could find without dismantling the roaster) from the drum to the fan so is the fan even effective at pulling air directly through the bean mass or is it pulling it in through the top and bottom chutes (and any other tiny opening) and then into the space between the roasting chamber and the thin, top cover? Or is that not the point of a fan in a drum roaster (to circulate hot gases through the bean mass)?

I guess it's time for me to start looking for the fan usage discussions here.

There is always something new to learn from you guys!