Roasting Dark with Smoothly Declining RoR

Roasted a couple of fairly dark Sumatras today that have pretty linear RoRs. This has been a challenge for me for quite a while so I thought I’d share the profiles:

https://beta.roast.world/@bradm/roasts/skFffArTK1u5ayzhtmYcm

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https://beta.roast.world/@bradm/roasts/Yhh_PYl8EhwEpY70N3r1z

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I’ve been having pretty good luck lately starting at P8 with 325g batches. Was originally worried that this much power with such a small batch might lead to scorching or tipping but haven’t seen any yet. To be on the safe side with this soft Sumatra bean, the first batch above started at P7 for a minute before going up to P8. I timed the fan increase to F3 in anticipation of an RoR jump at FC, which seemed to work pretty well. Dropped just before SC.

The second roast above was a back-to-back roast and a honey process bean, so I dropped the preheat to 190C and increased the initial P7 interval. The fan increase to F3 had a noticeable cooling effect on the RoR, but this bean loves to spike at FC so I added a short power dip. Again seemed to work pretty well, and dropped this one with a couple of snaps of SC in the pan.

I’m optimistic about these roasts, but… time will tell. Also eager to hear what others think.

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Thanks for the post Brad. I’ve had trouble getting to 2nd crack while trying to achieve the smoothly declining RoR (SDR) curve. These curves are textbook!

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I rarely go to 219C, but have a new bag of Sumatra to roast for friends, and will use this as a template. It looks real good. Thanks.

RIght, I don’t roast this dark too often either. Hoping these Sumatras will be the Java half of some holiday crowd pleasing Mokka-Java, combined with that Ethiopian Shantawene!

First brews today after 3 days rest: both roasts were initially quite bitter, but smoothed out nicely upon cooling. Some nice sweetness and complexity emerged in the honey process bean. Both roasts taste much darker than they look. No visible oil spots yet.

I, personally, have failed to reach SC in a satisfactory amount of time with a declining ROR. I do 1KG roasts, and after a lot of attempts at going dark with a declining ROR, have now switched to a rising ROR a minute or so after FC. I read somewhere in Sweet Maria’s blog about a declining ROR not always being possible, especially for dark roasts.

Entering FC at an ROR that is 7+ (at least) gives me a a comfortable level of momentum to control my roasts thereafter.

Ditto here. BTW, what is your batch size?

300 grams.

I’m adding heat after FC as well. See https://wilsonscoffee.com/pdfs/roastkit.pdf for a discussion of how Neal Wilson designs his roast profiles. If you inspect his profile plans for medium and dark roasts, you’ll see that his RoR increases after FC as well.

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Day 6 update: This roast of the honey process Sumatra bean (second pic in earlier post)

https://beta.roast.world/@bradm/roasts/Yhh_PYl8EhwEpY70N3r1z

has completely mellowed, losing the off-putting bitterness from day 3. A few oil spots are showing on the beans now. The brew has great creamy body with dark chocolate and walnut, and light sweetness with notes of cedar and spice that strengthen in a long finish. Very happy with this one. It will not last long :slight_smile:

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Any thoughts on how you would approach a larger batch size 500g or 800g? Increase charge temp? Higher power start? I have been struggling going from smaller batches to larger batches and getting similar results.