Hi all,

Last week, our roastery received the long awaited Diedrich IR-12.  Now that it is up and running and a few roasts has been performed on it, I'd like to ask those who know this roaster a few questions.

1. What batch size do you usually roast on it?

2. What is your expected turning point time & temperature?

3. When and around which temperature do you "usually" get to your first crack?

4. What is your roast development time between first and second crack (or time you drop when you don't get to second crack)?

5. According to the Diedrich Manual, they recommend to have the airflow 50/50 at 280f and in the drum (80/20) at 380f, do you roast using these airflow settings?

I am asking these questions because I used to roast on a Toper 10kg, in batches of 6kg, and my reference points are kind of tied to this roaster.  I am also asking because I get astringency on some coffees that I didn't get on the Toper.  Also, some coffees (i.e. Kenya) seem less intense than they were on the Toper.

I tried batches of 6kg, 10kg and 12kg.  The problem might not be the load itself but the way to bring the coffee to first crack or even airflow settings.

Any hints or comments would be appreciated!

Thanks,
Martin

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Replies to This Discussion

Afterburner? Manual or do you have the automation?

Optimum size seems to be 20 lb. green.

1:30 @ ~175

385 - 390 depending on coffee.

50/50 @ 270. You need the air in the drum at 370 - 380 to moderate the R/D and smoke build-up. You may need to lower gas 1-2 minutes away from drop depending on rate of rise. Tempting to lower gas at 400, but when you put all the air through the drum, that can cause a temp drop by itself. Good luck.
Thank you David.

We have no afterburner but we are using the automation.

Do you go full gas when you drop? At which temperature do you drop approximately? When do you reach first crack?

Here is an example of a profile I do when I roast 12kg of Brazil Cerrado on the Diedrich IR-12:

1. I drop at 415f, gas at 90%, airflow in the cooling bin
2. I get my turning point at around 1:30 at 170-180f (which seems quite low to me compared to what I'm used to)
3. At 205f, I lower the gas at 70% (If I don't, I get my yellow stage very early: in less than 5 minutes - also, I realized I need to adjust the roaster temperature where I want it to be in 2 minutes as it doesn't react very fast to temperature changes)
4. At 280f, I switch airflow to 50/50
5. At around 6:00 at 310f, I get my yellow stage
6. At 340f, I lower the gas at 10% (so that while I am between first and second crack, I get a good development, usually 3 to 4 minutes).
7. At 380f, I switch airflow to drum
8. At around 11:30 I get my first crack (385-390)
9. At around 16:30 I get my second crack (437-440)

Thanks for your feedback, really appreciated!
18 to 20 lbs is nice. 6 is very hard to control, anything less than that, and I start to get inconsistent.

Go with the profile that gives you the best flavors for the bean. If your not loving it, switch it up.

Perhaps if you want your Kenya a little brighter you could drop at 430+, and get yourself to first crack at 10:00+, kill your gas a bit early, and ride out the development to 12:00 without even getting near second crack.

I have had delicious coffees roasted on an IR-12 that were roasted in 9:00, and in 19:00. Do not be afraid to experiment.

That said, I find Davids advice to be very sound, particularly with the airflow through the drum at first crack, this is crucial for getting the smoke off of the beans.

Enjoy your roaster, my friend.
Hello Martin,
Just ran into this post and wondering how you have adapted to your IR-12? Do you have any issues with your current production?

Martin,

Totally forgot about this post until today and didn't realize you had follow-up questions. My guess is that 16:30 roast times you may be getting coffee that's a little flat, especially if the load is >20 lb. 

The turn time is exactly in the range I would expect.

I vary the drop temp as well. 400 for 6 - 12 pounds. 410 up to 20 lb. and 415 above that. Additionally, coffees with higher moisture content will require some additional gas and/or drop variations during the initial warm up phase of the beans.

Good luck-

David

Hello Timothy,

 

One of the realization I came to so far is that, although some roasters told me they could roast 12kg on their IR-12 and 24kg on their IR-24, I personally find that 12kg is too much for an IR-12.  We consistently get astringency on all coffees when roasted in batches of 12kg.  Not that I am surprised about this...

 

Our sweet spot is 9 to 10kg, depending on the coffee we roast.

 

The turning point is usually ~165f at ~1:30.  Compared to what I was used to on our previous roaster (~195-205f at ~1:30), I find it very low.  However, we were loading our previous roaster at 60-66% instead of 80% as is now the case with the Diedrich.

 

Our drop vary from 400f for decaf to 440f for high density beans like Kenya and Costa Rica for instance.

 

Generally, I tend to prefer the way coffee taste when I get my first crack around 11:00-11:30 rather than 9:30-10:00 for instance.  I also get a nice 3-4 minutes development before I drop.

 

What is also different on the Diedrich is that the "system" is slower to respond to gas changes than our previous roaster.  I need to think ahead of where I would like to be in 2 minutes...  Probably mostly due to the IR burners.

 

Also, although our Diedrich better develop (IMO) coffees than our previous roaster, I am always reminded that green beans quality is of utmost importance.  Hence, ordering samples and cupping is essential!

 

Hope this help,

Martin


timothy pellizzer said:

Hello Martin,
Just ran into this post and wondering how you have adapted to your IR-12? Do you have any issues with your current production?

Hello Martin,

I like you have recently converted from an 10KG atmospheric roaster. I seldom adjusted air with this roaster but with the IR-12 it is a different story. With the old roaster my first crack would seldom be longer than 10:30 but with the IR12 it seems to taste better at 11-11:30. I do not have a good feel yet for how to roast different types of coffee. For instance, should Kenya's be roasted to 1st crack at under 10:30? I hope to figure this out. If you or others have any suggestions please respond.

Also, do you find you are able to set your gas and leave it or are you constantly adjusting throughout the roast? I generally roast 15# per batch and charge temp is 390 degrees. If I bump up to 20-22# the charge goes to 400-405 degrees. At 2# the charge temp goes to 365-370 degrees. I am surprised how easily it was to go down to 2# and get a consistent profile.

Have you started to use your automation and if so how consistent are your results? I have throughly read Diedrich's manual and I think I understand their ideas. Under the profile development section they suggest roasting at least 10 batches of the same coffee to zone in on the right profile. Have you tried this technique or do you have an alternate solution? I think I would be drowning in coffee if I used this technique on every coffee.

I really like the way this roaster cleans up compared to my last roaster. The access doors are the right size for cleaning and if I clean throughly after each session the roaster never really needs a whole lot of scraping.

I have gotten used to the infrared burners and the time it needs to increase or decrease temps. The delta temp display has helped in making adjustments to temp.

I followed Diedrich's recommendation for seasoning the drum. I think it went well but I seemed to get a metallic taste on a few batches. I spoke to a roaster that claimed they had started a fire in their roaster and then put it out and repeated the entire process again. The claim was that the high temps, 650 degrees, somehow changed the structure or totally sealed the drum. The coffee was purported to taste much better after the fire. Did you try this? 

Tim

Hello Tim,

 

It looks like we are on the same page regarding the first crack time (around 11:00 - 11:30).  Regarding whether some coffees would benefit from having a quicker first crack (10:00 - 10:30), I'd say it depends on 2 things:

 

1) The quality/uniformity of the coffee you are roasting

2) To a lesser degree, the way it is intended to be infused

 

The theory is that the more heat you give to the coffee, the more some flavours (both positives and negatives) will develop and the more it will keep its brightness.  Hence, if you have a really really nice Kenyan coffee that you want to use for drip coffee, you might want to aim for a more energic roast.  From "The Balancing Act of Roasting Through Defects" in Roast Magazine:

 

"The seemingly radically low temperatures and high airflow can result in the balance needed to accentuate positive and control the negative in a much more even roast.  […] This more gentle profile will also be advantageous to charting a path for the other secondary defects.  […] A fast aggressive roast profile results in a sharper contrast between the defects and the other beans.  […] While the gentle, low temperature profile won't cure the problem, it seems to take the edge off."

 

I remember one of our coffee (a very nice Guatemala Atitlan La Providencia) actually came out better when first crack occured @ 10:00-10:30 than @ 11:30.

 

As for our current (winter) profile (note that we actually roasting 20-21# batches):

 

1. I drop at 415-440 / 70-80% gas / air in cooling bin

2. At 1 minute, we drop gas to 40-50%

3. At 280f, air to 50/50

4. At 365f, gas to 10-15%

5. At 370f, air to 80/20

6. At 415f, gas to 5-8%

7. If we go very dark (460f), then we turn off gas @ 450f and let it coast to it final temp.

 

Some references points: 

 

1. 240f @ 4:00-4:15

2. Yellow stage @ 305-315f @ 6:30-7:00

3. 340f @ 8:00-8:30

4. First crack @ 387-393f @ 11:00-11:30

5. Second crack @ 440-445f @ 15:00-16:00

 

As for the automation, I tried it twice and I was not really excited about it.  I could tell by blind cupping which coffee was roasted manually and which coffee was roasting using the automation.  The taste difference was more than obvious.  I did 2 batches of Yellow Bourbon, one after the other, same charge temp, same batch size/weight.  Using the automated profile I had just recorded, the automation was driving gas in a crazy way: sometimes at 100%, sometimes no gas at all.  Always varying the amount of gas instead of giving the coffee a uniform heat environment.  I might be wrong, but considering I could differentiate both batches by blind cupping is not what I consider a positive result.  I am far from being a Diedrich automation expert though!  I would have preferred an automation system that let you specify gas value instead of time/temperature so that I can control gas intensity.  While I am not a 25 years old experienced roast master, my understanding/belief is that heat uniformity is an important part of the equation here, not only time/temperature.

 

As for the cleanup, I also really like the Diedrich, easy to maintain and clean!

 

As for drum seasoning, I only did what Diedrich recommended.  I didn't started a fire in the roaster :-)

 

I'd be curious to know what you current "typical" profile looks like.

Martin

Hello Martin,

Thanks for all your insight. I have not loaded any profiles into the automated system. I hope to try it soon but your experience concerns me. I was under the impression that the system would replicate the time/temp sequence allowing the coffee to taste the same as when roasted manually. I will keep you posted. 

Here are a few my recent profiles:

1. Guat Peaberry

    wt. 15.25#

    Charge temp 390 degrees

    Finish temp   420 degrees

    Air set to 20%

    Flame at 5%

    Bottom out at 1:34 at 173 degrees

    50% air at 5:00 minutes at 260 degrees

    Flame changed to 10% at 8 minutes at 318 degrees

    Flame changed to 20% at 10 minutes at 345 degrees

    Flame changed to 50% at 11 minutes at 357 degrees

    First crack at 383 degrees at 12:50(a bit late)

    Flame changed to 70% at 12:30 at 372

    Finish at 420 degrees at 14:48

 

2. Yirg

    wt. 14.25#

    Charge temp 390 degrees

    Finish temp 430 degrees

    Air set to 20%

    Flame at 5%

    Bottom out temp 171 degrees at 1:32

    50% air at 5:00 at 274 degrees

    80% air at 11:00 at 371 degrees and flame changed to 20%

    First crack at 12:12 at 388 degrees

    Finish time at 15:17 at 430 degrees

 

3. Sumatra Wahanna

    wt. 13#

    charge temp 390 degrees

    Finish temp 425 degrees

    Air set to 20%

    Flame set to 5%

    Bottom out at 1:30 at 182 degrees

    Air at 50% at 5:00 and 284 degrees

    Air at 80% at 10:00 and 373 degrees

    1st crack at 10:28 and 381 degrees

    Flame to 0% at 13:00 and 410 degrees

    Finish at 14:37 at 425 degrees.

I have found when reviewing all my profiles that my first cracks are consistently too late. Perhaps if I can get them into the 11-11:30 area my coffee may taste better. I will detect a off taste that I would describe as cardboard in some of the coffees. Please let me know if you have any other suggestions.

Tim

 

 

 

Hello,

Just came across this discussion and it's great to read about the experiences of roasters using the Diedrich machines! I've recently started roasting on an IR1kg and have an IR-12kg for larger batches. The IR-1kg is a great machine for developing roast profiles, so that you don't use up a lot of beans while trying to tweak the best profile for the beans. 

 

A question on flame settings - when flame setting is mentioned as a % what is corresponding reading on the manometer in inches water column ("WC)? I understand that the factory setting on the Diedrich is set at a max of 7"WC - are you referring to % of this max setting?

 

Clearly, profiles are very much dependent on bean origin; in my experience a Kenyan peaberry (5,000ft) needs a higher initial gas setting (I generally drop at around 385F, with minimum gas setting of 1.5"WC, increase gas to 6"WC after 1.30 sec bottom out, slow temp increase after 5mins to 4"WC; reduce gas setting again at 9.30 to 2"WC; 1st crack around 10 mins at 383F and then have a long slow Roast Development of over 4mins. I have found that the peaberry needs a long RD to accentuate the grapefruit notes of this bean. Shorter RD times do not bring out this unique flavor. I have had similar results with beans from El Salvador (3900-5250ft) - i.e. high flame setting after 1.30 sec bottom out. 

 

A bean grown at a lower altitude (Brazil at 3100 feet) requires lower gas setting after 1.30 second bottom out, to achieve a 1st crack around 11 mins.

 

However, the biggest influence on flavor is the roast development time - it seems to be critical not to rush this, by reducing heat before 1st crack and allowing beans to cook very gently before dropping. It seems to me that a good reporting parameter would relationship between RD time and temp increase per second during RD - so for example a 3 min RD with a temperature increase of say 40F (0.22F/sec) from 1st crack to drop will be much different than a 3 min RD with a 60F (0.33F/sec) temp increase.

 

Kevin 

 

 

 

Does anyone have any general principles on scaling up from a 1kg to a 12kg? I understand that generally increasing batch size requires an increase in the initial charge temperature.

Hello Kevin,

 

The gas % refers to the amount of gas you ask the automation when roasting in manual mode.  If you don't have the automation, your reference point becomes the WC instead of percentage.

 

Also, IMO, you are totally correct by mentioning some coffees require more initial heat than others.  I don't apply the same amount of energy when roasting a Costa Rica compared to when roasting a Brazil for instance.  Bean density is a good indicator of the required profile.  Boot coffee has very interesting articles on the subject.

 

Martin


Kevin said:

Hello,

Just came across this discussion and it's great to read about the experiences of roasters using the Diedrich machines! I've recently started roasting on an IR1kg and have an IR-12kg for larger batches. The IR-1kg is a great machine for developing roast profiles, so that you don't use up a lot of beans while trying to tweak the best profile for the beans. 

 

A question on flame settings - when flame setting is mentioned as a % what is corresponding reading on the manometer in inches water column ("WC)? I understand that the factory setting on the Diedrich is set at a max of 7"WC - are you referring to % of this max setting?

 

Clearly, profiles are very much dependent on bean origin; in my experience a Kenyan peaberry (5,000ft) needs a higher initial gas setting (I generally drop at around 385F, with minimum gas setting of 1.5"WC, increase gas to 6"WC after 1.30 sec bottom out, slow temp increase after 5mins to 4"WC; reduce gas setting again at 9.30 to 2"WC; 1st crack around 10 mins at 383F and then have a long slow Roast Development of over 4mins. I have found that the peaberry needs a long RD to accentuate the grapefruit notes of this bean. Shorter RD times do not bring out this unique flavor. I have had similar results with beans from El Salvador (3900-5250ft) - i.e. high flame setting after 1.30 sec bottom out. 

 

A bean grown at a lower altitude (Brazil at 3100 feet) requires lower gas setting after 1.30 second bottom out, to achieve a 1st crack around 11 mins.

 

However, the biggest influence on flavor is the roast development time - it seems to be critical not to rush this, by reducing heat before 1st crack and allowing beans to cook very gently before dropping. It seems to me that a good reporting parameter would relationship between RD time and temp increase per second during RD - so for example a 3 min RD with a temperature increase of say 40F (0.22F/sec) from 1st crack to drop will be much different than a 3 min RD with a 60F (0.33F/sec) temp increase.

 

Kevin 

 

 

 

Does anyone have any general principles on scaling up from a 1kg to a 12kg? I understand that generally increasing batch size requires an increase in the initial charge temperature.

Thanks Martin!

 

I opted for the manual roasters so I'm working with "WC. I attended some of Willem Boot's courses in Mill Valley CA. Although he does not yet roast on a Diedrich for training purposes, his courses were a superb introduction to the art of roasting. 

 

It's great to find some roasters using the Diedrich machines on this forum!

 

Best of luck,

 

Kevin 

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