What's too fast during various phase from 300f BT to start of first crack. Especially between 300f and 350-60f BT. Wondering if there are points where you can/should go faster and points to slow a bit. Of course each roasters range would need to be considered for it's heat transfer abilities and limits.
It seems the rate can accelerate easily from 300-350f and then is more energy demanding from there to first. Generally I'm in the low 20s rise/min and high teens coming into first. If I speed the ramp after drying I can get in the upper 20s low 30s at about 320 to 350f but even with good heat transfer am wondering if that rate is too fast?

With the P1 air roaster, I go at around 30F/min, which is the speed limit, in terms of MET, for the highest loads I do on it, 180 grams. I can get that fast on the Quest with 120 gram loads, but I've slowed down to around 20F/min instead.

My take is that on the P1, and maybe all air roasters, a slow first ramp just flattens the taste and reduces the sweetness. On the Quest I'm finding that a slowed down first ramp adds a nice malt/oak/toast thing to the coffee that I can't get at all from the P1. On the other hand, going very fast leaves the roast tasting kind of raw rather than getting the transparency of the P1. It's a bit like the difference between an oak and steel barrel aged wine; the best way depends on the wine and your mood.

The Quest is a lot more of a fun roaster, albeit more work, than the P1. So I've been playing favorites by exploring these oak barrel flavors, and haven't worked on the differences. However, I'm pretty sure you can developing these flavors on an air roaster is difficult or impossible. This makes the Quest, and maybe all drum roasters, better for Bourbons and the related East African varietals. On the other hand, for the big fruit bomb Ethiopian varietals, where just about all roast flavors are a distraction, I think the air roasters (and the heat gun/bread machine style roasters) may be better.

My speed limits from 300-400F (Poppery I with BT, MET, variacs on fan and heater) derive from a couple factors; From 300-370F BT, the limit is determined by how much heat (how high MET) the beans can soak without getting uneven and roughed up. Setting the MET 80-90F above the BT is about the maximum on my roaster and this will get 160gram of beans to 33F/min or so. I think 30F/min is a good 'safe margin' speed limit.

What happens above about 370F BT; On a fast ramp, I've reached my MET for first crack (usually 460-465F) I will hold this MET for the duration of first crack. As the BT continues to climb closer to MET, the roast must slow down here. (380-400F BT, may take a minute or more) I generally don't like the results if MET temps exceed 470-475F for too long. I save that (if needed) for the last minute of roast.

Edit:(had to fix some MET's that were off by 100F)

This is very timely information! I had a conversation this afternoon with another home roaster about this very subject. I recently roasted two coffees (Rwandan and Colombian) on my P1 using 23f/min from 300 to 280 F. I felt both coffees were too flat and not dynamic enough. I was wondering how fast I could go. I'll try 30 F/min. I don't have my ET probe in yet, but my PID (Fuji) did arrive today.

Thanks

OT P1 tip: You may want to take off the case, and insulate the air space between the roast chamber and the case. This will virtually guarantee that if you follow a reasonable profile on the beans, you won't go too high on the MET. If you have an uninsulated roaster, the MET can get quite high on a fast ramp to the first.

another_jim wrote: ..............................
My take is that on the P1, and maybe all air roasters, a slow first ramp just flattens the taste and reduces the sweetness. On the Quest I'm finding that a slowed down first ramp adds a nice malt/oak/toast thing to the coffee that I can't get at all from the P1. On the other hand, going very fast leaves the roast tasting kind of raw rather than getting the transparency of the P1. It's a bit like the difference between an oak and steel barrel aged wine; the best way depends on the wine and your mood.
..................

I'm still dreaming I can have both these roasters rolled into one; Variable forced air convection, mechanical agitation, the convection/blower to heat both the vessel and/or the beans directly. The HG/BM requires higher air flow directly to the bean mass, the vessel heated indirectly and a popper requires constant manual stirring at the much lower air flow rates required for this kind of roast.

Slowing a roast by lowering air flow instead of ET has different effects on the result.
I don't understand why, I've been working this for about 3 months now; maybe a simple ET-BT time/temperature effect or the high air flow in a fluid bed 'stripping the volatiles' as I have read a theory or speculation... Whatever, it is clear to me the air flow knob is a good one to have a control on.

Right now it looks like the Quest has the most convection control of any home drum roaster.
(....or the only one with a blower that enhances convection.)

Convection effect on the Quest: for a 200 gram load, keeping the drum temperature fairly constant, maybe 75 seconds faster with max air (and max heat to hold the ET fixed) for the ramp to the first than with minimal airflow.

The effect gets more dramatic as the bean load is decreased, up to about 2.5 minutes for a 1/4 pound load; at which weight 8 to 9 minute sample roasts are possible. I read an article where the convection effect is calculated in terms of airflow/bean load, so that lower charges don' just get faster roasts, but a wider range of profiles. Weight changes on the Quest seem to confirm that. So now I do fast 112 gram sample roasts, and leisurely 150 to 225 gram drinking roasts. However, even on the sample roasts, I get more of that oak-malt drum taste than with the P1.

For a solid drum I would speculate that bean bed depth might be a better variable than bean load in the airflow/bean load calculation, at least when comparing different diameter/length drums.
With a lower bean depth in the drum, the average bean spends more time against the drum in the hot boundary air layer.

On a separate thought, could the drum surface temperature be hotter at max airflow and same ET reading?

Good concrete question! I think you're right about the layer depth. Not sure about the drum temperature, what would make it hotter at higher airflow?

Frost wrote:I'm still dreaming I can have both these roasters rolled into one; Variable forced air convection, mechanical agitation, the convection/blower to heat both the vessel and/or the beans directly. The HG/BM requires higher air flow directly to the bean mass, the vessel heated indirectly and a popper requires constant manual stirring at the much lower air flow rates required for this kind of roast.

In the Quest M3 roaster you could stick a heat gun through the trier hole. I have an old Sears heat gun that has a reduced tip that would fit inside the hole. That would be make it a hybrid

Cheers