April 2021 Roasts
Bean: Colombia Sergio Cocha Cauca FW from Sucafino (see link for specs)
Machine: Giesen W15A (at Settlement Roasting Collective)
1st batch
When comparing this roast to the others we need to keep in mind that this batch was the first batch of the day for the roaster (can be different in a co-roasting space) so even though we gave the machine plenty of time to warm up, the front plate doesn't get fully heated until after the first roast because it needs beans roasting against it (airflow alone isn't enough).
Roast weight 12 kg / 9.9 kg (-17.5%)
First crack: 09:44 - 193.1°C
Duration: 12:32
Dev. time: 02:48
Dev. time ratio: 22.3%
Start temp: 210.7°C
End temp: 205.5°C

Download the CRC file here.
2nd batch
Roast weight 12 kg / 9.9 kg (-17.5%)
First crack: 09:15 - 193.4°C
Duration: 12:09
Dev. time: 02:54
Dev. time ratio: 23.9%
Start temp: 213.5°C
End temp: 205.4°C
Download the CRC file here.
Comparison of batch 1 and 2
Blue is the 1st batch, red is the 2nd
So firstly, both were 12kg charges and had the same 17.5% moisture loss. The 2nd batch started a bit higher but both end temperatures are the same. Difference in the roasters thermal energy given first batch was the first of the day for this machine.
In the second batch the gas goes to 100% a bit earlier but then steps down way faster to try to push the ROR down before first crack. The finish temp is hit a full 30 seconds before the first batch.
In blind cupping soon after the roast, the second batch had more body and sweetness than the first.
The modulation chart from Cropster shows pretty modest differences in Maillard and Development phases:
Very happy with the result in the cup for that second batch.
3rd batch
Roast weight: 12 kg / 10.2 kg (-15%)
First crack: 09:21 - 193.2°C
Duration: 12:04
Dev. time: 02:43
Dev. time ratio: 22.5%
Start temp. 214.9°C
End temp. 206.1°C

Comparison of batch 2 and 3 (3 is blue):

Looking at this comparison, while I reduced the gas earlier on the 3rd batch, I did it in smaller steps and so hit first crack later. Roast time was the same so the 3rd batch spent less time in development, which you can see in the modulation chart comparison (3rd batch is the top bar):

4th batch
Roast weight: 12 kg / 10.2 kg (-15%)
First crack: 09:02
Duration: 11:32
Dev. time: 02:30
Dev. time ratio: 21.7%
Start temp. 213°C
End temp. 206.1°C




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