What is the expected Rate of Rise drop at 1st crack? I am getting a 10°F RoR drop in the 1st section of 1st crack as can be seen in the graph. Is this in the "normal" range?
From the same RoR curve, there is a steep decrease up to roughly BT 280°F (4.5 min). Is it possible that it is an early indication of the end of drying?

[quoteWhat is the expected Rate of Rise drop at 1st crack? I am getting a 10°F RoR drop in the 1st section of 1st crack as can be seen in the graph. Is this in the "normal" range? ][/quote]

Normalcy would be in the context of a specific coffee for that drop. In some wet hulled Sumatras I got similar output on Artisan. The roasts were not bad, so I have come to accept that type of drop for the wet hulled Sumatras. Other coffees show differently.

For the RoR after 1C, I think that totally depends on roaster settings going into 1C. For me personally the 10 degree drop that fast would be a little too drastic so I would combat that to get a more constant decrease. I personally go into 1C with a little more velocity than you. What are you doing the 20 degrees before 1C? Any burner adjustments to avoid the flick or any airflow adjustments when 1C begins? What roaster are you using?

On point 2, agreed with roastimo, it kind of depends. Depends on the beans and in my case what batch I'm on that day. Early batches give more fluctuation so I sometimes combat decreases with minor burner increases a couple of minutes into the roast. I've never tested 2 batches, 1 with a decrease and 1 without, to look for a difference so I'm not much help there. Might be a good experiment for me sometime

mfortin wrote:What is the expected Rate of Rise drop at 1st crack? I am getting a 10°F RoR drop in the 1st section of 1st crack as can be seen in the graph. Is this in the "normal" range?
From the same RoR curve, there is a steep decrease up to roughly BT 280°F (4.5 min). Is it possible that it is an early indication of the end of drying?
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Not particularly unusual on my roaster and most of my graphs match yours to the extent they show quick enough recovery back to trend that I don't worry about it.

I can increase airflow slightly in anticipation of the beans going exothermic coming into first crack to carry away a little excess heat. I can then time a small bump in heat, small enough that my BT ROR is still declining, to counter the evaporative cooling associated with first crack. I can't say definitively how much any of this impacts the cup. Probably not much, but I really like my coffee and it makes me feel like I'm doing something.

My inclination is that this blip is less of an impact on roast quality than a well chosen end point. I think 3-4 degrees difference in the drop temp (at 10F ROR, 20-30 seconds) is much more potentially deleterious than the brief dip in your recorded ROR.