Yesterday I roasted two batches, the first was spot on, the second was a disaster. I am guessing that the thermal conditions were not consistent from batch one to batch two at the start of the roast. Does anyone who roasts with a Cormorant have any suggestions as to how to approach the between batch protocol? I am thinking that the roaster needs to cool down more so maybe gas off, drum off, diffuser open and airflow at maximum? Not sure about drum speed off, but I am thinking that makes sense.

Any suggestions are appreciate. Thanks!

Do not warm it with the drum speed off. That will create a hot spot at the bottom of the still drum.

I heat it up to 40 degrees above my charge temp with the gas at 10 and then turn the gas off until it is 30 degrees below charge temp. Then I turn the gas on (10 again) to go up to my charge temp. If I do this for my first roast of the day I find it easy to repeat that roast and don't have any issues with each batch running a tad hotter and faster.

I also make sure that when BT gets to charge temp that my ET is the same ET as last time at Charge. If not I will cool down a bit and reheat again to get it right.

Doing this I hit all of my milestones within 2-4 seconds for all of my batches. It is actually a pretty nimble machine for better or worse.

This all sounds good. I will give it a try. Thanks! BTW, in your other post you mention a damper. Do you mean the diffuser knob or is there something else. I am not familiar with that if it isn't the diffuser.

There is a flower valve that draws air through the cooling basket. I am not talking about that.

I am talking about the wood handle on the motor side of the roaster that opens and closes a grate below the drum and directly above the burner.

The second image in my thread shows this on the disassembled roaster.

I too find it confusing with this damper/diffuser talk because it usually refers to airflow. But in this case it is about direct or indirect heat application.

I don't own a Cormorant. Instead I roast on a Mill City 1K. It has gas burners and fine airflow control which may be thermally similar to a Cormorant. What I found is that there is a difference between first batch protocol and subsequent protocols. The first roast suffers from a lot of metal which never gets to the same temperatures as after a batch. And depending upon how you warm the roaster, it may never match no matter how long you let it sit warming.

IMO, the worse warming protocol results in very low flames at a target BT or ET temp. There is no beans in the roaster, so it takes very little burner to maintain the temp. But with low burner, the metal outside the drum never stabilizes at the correct hotter temps that occur during a roast.

The better approach is to keep airflow higher, perhaps a bit higher than when roasting, during warmup. That way, burner setting at steady state temps will remain pretty high. The higher burner will heat outside metal more. And as you already do, warm to say 400-420F and then bring temps back down to desired charge temps. This way, the metal throughout the roaster will more closely match temps after a batch.

That said, with my roaster, I still have significant differences in temps when I do everything like this to minimize deltas. First batch is tough to get perfect match to later batches. Maybe with the Cormorant it would be easier.

EddyQ wrote: IMO, the worse warming protocol results in very low flames at a target BT or ET temp. There is no beans in the roaster, so it takes very little burner to maintain the temp. But with low burner, the metal outside the drum never stabilizes at the correct hotter temps that occur during a roast.

The better approach is to keep airflow higher, perhaps a bit higher than when roasting, during warmup. That way, burner setting at steady state temps will remain pretty high. The higher burner will heat outside metal more. And as you already do, warm to say 400-420F and then bring temps back down to desired charge temps. This way, the metal throughout the roaster will more closely match temps after a batch.

That said, with my roaster, I still have significant differences in temps when I do everything like this to minimize deltas. First batch is tough to get perfect match to later batches. Maybe with the Cormorant it would be easier.

Hmmmm...excellent point. I hadn't thought about it that way. Maybe the fact that I get the roaster to 40 degrees above charge temp and then let it drop below before heating back up to charge let's me avoid the issue?

Either way, thanks for pointing that out!

General comment; Rao has good content in "Coffee Roasting Best Practices" on setting up warming and between batch protocols. Highly recommend this book for a number of reasons including this.

Another comment; I try to hit a common TP for a given bean/roast regardless of whether it's the first roast or later roast in the day. I find if I can achieve this common anchor point I can control the rest of the roast the same. To achieve this common TP I will usually drop my charge temp after the first roast. YMMV but worth looking into.

Brewzologist wrote:Another comment; I try to hit a common TP for a given bean/roast regardless of whether it's the first roast or later roast in the day. I find if I can achieve this common anchor point I can control the rest of the roast the same.

+1

On my cormorant, I've noticed that having the diffuser (handle by the motor) in the open position when warming causes the BT/ET to heat up faster than when diffuser is in closed position. Also, once I dropped a batch and didn't notice the diffuser handle slid to the open position during dropping - I noticed it and changed just before charging the next batch. That caused the next batch to behave unexpected... tasted good, though. From now on I always check the diffuser position when I start the next heating cycle.

When it is in the open position the flame is directly heating the drum and more specifically, the outside of the drum first. The probe in the tilt handle position is outside the drum but in the small space between the drum and the metal frame around the drum. For this reason the ET probe will read much higher on warmup and higher throughout with the damper in the open position.

I don't know if other roasters give you the option of direct/indirect heat like this as well as the changes in airflow temp associated with it but it does give us a lot to play with in creating a profile.

Until recently I had only roasted with it in the open position but look forward to learning from playing around with this.