New to gas roasting - please help!

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
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#1: Post by ShotClock »

After years of using relatively underpowered electric roasters, I have recently acquired a used Cormorant. As you might imagine, this is quite a new experience for me. After a few mostly undrinkable roasts, I have one drinkable (but not very good), and another that looks like it will be drinkable (will try over the next few days).

The coffee is an espresso blend from Sweet Maria's, which I'm quite familiar with. I was aiming for full-city, hoping to hit 1C in ~9 min and drop in 11-11:30 with 20% development time. I had found this to be a reasonable profile on the hottop.

Here is attempt 2, my first reasonable roast:

I charged with the gas at 25 mbar, and felt like it took off too fast. I was trying to slow things down, but never managed to get it slow enough. There was a bit of a crash at 1C, I assume that this is from going in too fast (other roasts with even higher RoR at 1C exhibited a massive crash, and in one case, a complete stall with RoR < 1F/min). Examining the beans, I think this was dropped too quickly, and was maybe city/city+. The result is rather unpleasantly acidic, although there are no grassy or major underdeveloped flavours. From the description on SM, this is probably to be expected at this level of roast,

Here is attempt 4, second reasonable roast:

Here, I charged at 15 mbar, and soaked until 1 min before increasing the gas to 25 mbar. I think perhaps I cut the gas too aggressively toward DE, and lost too much momentum before 1C. I also went in to 1C a little hot, since I was trying to keep the roast short, so there was a bit of a crash. The roast looks like a well developed FC, but I suspect it will be a bit on the baked side.

Am I going in the right direction? Are my targets reasonable? Is my approach to achieving them going to work (once I can operate the controls a bit better)?

Any and all comments and tips are gratefully received!

Edit - fixed the wrong image for the second roast.

ShotClock (original poster)
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#2: Post by ShotClock (original poster) »

Update - after cupping both roasts, they were actually both pretty awful. Unpleasant acidity, bitter roastiness, and some grassy under roasted notes in one of them.

Will attempt to stay on the gas a little longer in the first half, then cut a bit more in the second half so I get to 1C with a bit less momentum next time.

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#3: Post by mkane »

You get the idea. Try not to raise the gas after DE. Practice makes perfect. Keep at it and relax. Coffee roasting is better than meditation.

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#4: Post by drgary »

Here's a current thread where professional roaster Almico writes about how he uses his Cormorant, starting at the post linked below:

Roaster preheat, soak, etc.

What I WOULD do for a good cup of coffee!

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#5: Post by CarefreeBuzzBuzz »

As Alan mentions in the thread linked, the Comorant doesn't store much thermal heat. That means you probably shouldn't soak but might help to get to DE a little faster and don't increase heat after DE.

These roasts don't look underdeveloped, maybe over roasted, in this roaster compared to what you were doing on the electric one. Did you give it a good cleaning?

Instead of focusing on developing time, I have a different suggestion for making this transition.

Update Artisan to 2.4.6 if you haven't. In Statistics, make sure the ∆F is selected. Also in Phases, make sure Phases LCD All is checked. With these two watch the temp difference after FCs. Forget about the % so long as its say 14 or more. Try to see what ∆F after FCs you like for a particular coffee. You could start with comparing that between roasters.

After talking to many people using Artisan, I don't believe the 20% has any magic and people have been able to identify someones taste desire more by looking to these temps. Many coffees don't need 20%.

Also fyi black background themes are hard for some people to read on smaller screens.

If you then like this, note that you can save this data in the file name with Autosave function. Also if you explore Config>Events, Annotations tab, you can show your heat changes and temps on your stair steps. See the Quick Start Guide and Blog.

Good luck.
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ShotClock (original poster)
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#6: Post by ShotClock (original poster) »

Thanks for all of the tips and advice. I hadn't seen the thread with Almico explaining his usage of the Cormorant - it was very illuminating, even if he is using much smaller batches than most of us. I hadn't realised that the thermal mass was so low, so will abandon soaking from now on.

I have been taking advantage of my time of work, and got another couple of roasts this morning. Getting better, but not sure if these will just go on the grinder seasoning pile. Fortunately, grocery store coffee can be George Howell for me, so I won't be forced to drink something unpleasant...

Here is today's first roast. For both of these, I set air to 6V and left the damper open all of the time - just making changes with the gas.

I charged lower, but forgot to bump the gas up to 25mbar beforehand. Had to increase the gas toward DE, but was still too slow at 5:30. A bit of a crash during 1C, but not too bad. I suspect this may be baked, as it was generally too slow everywhere - 6:18 from DE to 1C is 50% more than I was aiming for.

Here's the second roast:

Charge was a little higher, and at 25 mbar this time. I was too aggressive again in cutting gas in the middle of the roast, maybe should wait until after DE next time. Should have also made my final gas reduction 1 minute or so earlier, as I did so right before 1C and got a bit of a crash. This one might be drinkable though, only 12 min, but still slow compared to my plan.

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#7: Post by drgary »

The hump before 1C on both roasts suggests you may be coming into 1C with too much energy.

What I WOULD do for a good cup of coffee!

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#8: Post by LBIespresso » replying to drgary »

This hump leads to the crash and the following flick. Cut gas before the hump and that should help you ease into FC with less of a crash. then you can cut gas at around whatever temp you have at 13 minutes to avoid the flick.

I would charge hotter and kick up the gas earlier. This will get you done sooner.
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#9: Post by akirapuff »

how big are your batches? I charge at full 42 mbar from beginning to DE for a 500g batch.


#10: Post by srosemer »

On the earlier roasts, it looks like your RoR stalled and was followed by a flick and crash. The last roast profile you shared wasn't as dramatic of a flick and crash and your RoR didn't stall so I suspect the result was more to your liking. It looks like you're calibrating your way through things. I only have a few suggestions that may assist you with your calibrating efforts:

1). Use the same roast size each time.
2). Do multiple roasts and develop a warm-up routine so that your first roast is as predictable as your 2nd, 3rd, and so on.
3). Practice to establish a consistency routine for both gas and air to get consistent profiles, then experiment with charge temps, RoR max and slope, etc.
4). Rescale your curves in artisan to show RoR in degrees/30 seconds, with a max RoR of 15-20 degree/30 seconds. To do this go to "Config Curves", go the RoR tab, and change the delta BT Y(x): type in x/2 into the text box. Doing this will enable you to compare your roast profiles to both textbook profiles as well as those of profiles shared by the handful professionals who do share.

You're kind of doing step 3 now so have low expectations on roast quality for a while. Do your best to reduce the number of variables to shorten the learning curve related to the dynamics of your machine. Consider buying a lot of less expensive green beans for the learning process. Your friends, neighbors, and family will enjoy even your worst roasts, as they are likely to be far fresher and more enjoyable then anything they will buy in their local grocery stores,