Learning to roast on Quest M3s - Page 4

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
Cwilli62 (original poster)

#31: Post by Cwilli62 (original poster) »

I am having a really tough time getting a good roast. I roast outside so I took a break for the coldest months of winter but now the outside temps where I live are nice during the day. All of my roasts are quite underdeveloped. Shown here is my most recent roast session. On these, I was trying to push the heat at the beginning of the roast. I ALWAYS have trouble keeping my ET down. It ventures into 600F, sometimes as high as 625F though I try my best to keep it lower but find it hard. It has been said that for this machine's health it is best to keep the ET much lower.

"D" is drum setting in Amps (I am still not using the Kill A Watt though I know it would help) expressed as if there is a decimal before the last digit (ex: 100 is 10.0, 85 is 8.5). "A" is fan speed using the same concept. 8.5 is the highest setting on my machine. A friend recently suggested that on previous roasts I was not getting enough airflow so I tried starting it on full speed and leaving it there the whole roast.

Any suggestions or ideas?

Kenya Nyeri Kiandu AB
Ambient temp around 65F
114 g per batch





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Jonk

#32: Post by Jonk »

Have you tried higher charge temperature? In Coffee Roaster's Companion, Scott Rao suggests 380-440F as a reasonable range. This led me to try higher temperatures than I used to do and it seems to work nicely.



Sorry for the lack of annotations. This roast of 190g* Ethiopian Limu started at 1000W, down to 600W already by 6:00. Smoothing set to 0 and delta span 15, FWIW.

*easier to control than much smaller batches in my experience.

I don't measure MET but would be interested to hear what you end up at.

RobertL
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#33: Post by RobertL »

I had a very similar problem to yours. My solution ended up being air flow related. The chaff drawer at the bottom of the roaster wasn't closing completely this was messing up the air flow. The chaff drawer seats at an angle and the top of mine wasn't sealing completely. Like you, my MET was running high and RoR low. I ran an empty roast with and without the drawer cracked open and the results were obvious.

edgndg

#34: Post by edgndg »

2 thoughts:

1. I'd definitely charge higher - I've been doing 380f lately which seems to work well;
2. It really helped me to read the Rao best practices book WRT to the between roast protocol. I had been trying to have sort of a flat, stable temp when I charged. He suggests lowering temp to about 40 degrees below your charge temp and then rising rapidly to hit it - I do use a KOW and I'm doing about 1000w with fan on 4 charging as it hits 380. These are on 200g roasts.

Cwilli62 (original poster)

#35: Post by Cwilli62 (original poster) »

Jonk wrote:Have you tried higher charge temperature? In Coffee Roaster's Companion, Scott Rao suggests 380-440F as a reasonable range. This led me to try higher temperatures than I used to do and it seems to work nicely.

Sorry for the lack of annotations. This roast of 190g* Ethiopian Limu started at 1000W, down to 600W already by 6:00. Smoothing set to 0 and delta span 15, FWIW.

*easier to control than much smaller batches in my experience.

I don't measure MET but would be interested to hear what you end up at.

Before a couple of weeks ago, I was charging at 350F. Dropped the charge to try to extend the drying phase a bit. I suppose, though, that a higher charge temp will help to get that heat going into the beans at the beginning of the roast. I'll give it a try. Although I have been doing batches that are smaller than the ones that y'all are talking about. The idea was to try to get more roasts in per session. So as a second thought, perhaps I will try larger batches in the next session.

Also, I'll start measuring Wattage so that I have the proper common language to compare power settings with you all.
RobertL wrote:I had a very similar problem to yours. My solution ended up being air flow related. The chaff drawer at the bottom of the roaster wasn't closing completely this was messing up the air flow. The chaff drawer seats at an angle and the top of mine wasn't sealing completely. Like you, my MET was running high and RoR low. I ran an empty roast with and without the drawer cracked open and the results were obvious.
Interesting. I just took a look. Embarrassingly enough I didn't even know that that compartment was down there. :oops: There was some charred chaff in it....so..... Anyway, I cleaned it out and will keep an eye on that drawer to make sure that it is closed properly when I roast next week.
edgndg wrote:2 thoughts:

1. I'd definitely charge higher - I've been doing 380f lately which seems to work well;
2. It really helped me to read the Rao best practices book WRT to the between roast protocol. I had been trying to have sort of a flat, stable temp when I charged. He suggests lowering temp to about 40 degrees below your charge temp and then rising rapidly to hit it - I do use a KOW and I'm doing about 1000w with fan on 4 charging as it hits 380. These are on 200g roasts.
I just finished Rao's book and will play around with/get better with my between roast protocol.

I appreciate the insights and thoughts from the community!

equin0x

#36: Post by equin0x »

Three more ideas:

1. Look at your RoR temperature at first crack. There is hardly any development going on you can also see that the bean temp is not going up anymore. That could easily explain why it tastes underdeveloped, probably the degree of development is nearly the same as before the crack.

2. What usually works for me is to do my last power adjustment one minute prior to the beginning of the first crack. Looking at your graph I'd keep it at D70 and lower it only when the crack is already rolling for at least 30 seconds.

3. As you are roasting quite small batch sizes max airflow could be too much. Maybe try medium airflow throughout the whole roast and only max it out a few secs at the end to blow the chaff off.

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Peppersass
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#37: Post by Peppersass »

What size probes are you using and where are they placed? For reference to the description below, my probes are setup as described by erics. My MET probe is 1/16" placed between the drum and outer shell. My BT probe is also 1/6" to the right of the sight glass in the drop door. I have a 1/8" BT probe in the hole where the original analog thermometer was, as well as a 1/6" probe in the exhaust tube. I haven't found the information from those probes to be useful.

14g is close to the lower limit for the M3s. With a batch that small you'll have difficulty controlling the roast. I started out with 150g batches and eventually moved up to 175g to improve control. Not sure I'd go over 200g for fear of not getting enough heat into the beans to carry through the roast without tipping, scorching, raising MET too high, etc.

Typically, I charge in the 365F-385F range, with MET running about 480F-500F to keep the charge temp stable. I'm familiar with the idea of lowering the charge temp (e.g., by opening one of the doors), letting it rise and charging when it hits the target temp, but I haven't done that in a while. Instead, I wait until the TP, then increase MET. For example, if MET at charge is 480F, I'll bump it to 500F-520F at the TP. Then I don't touch heat until 1-2 minutes before FC, typically around the 90 second mark. Then I'll lower MET back to where it was at charge, say 480F.

I should point out that my roaster has an Arduino TC interface with PID. There's a switch to enable/disable the temperature dial, which is bypassed when heat is controlled by the Arduino. So, I set target temperatures for MET in Artisan rather than dealing with amp settings. But I don't think that's significantly better than learning to set MET by amps.

My fan speed is controlled by the Arduino, too, as a percentage of max. 25% gets the fan barely moving. I used to start roasts at 30%, but since replacing my M3 drum with an M3s drum I start out at 40%. Once RoR reaches peak. I increase fan speed to 50%. Right around Brown (about 90 seconds after DE), I increase fan speed to 60%. About halfway through first crack I increase fan speed to max to blow off any remaining chaff (I roast a lot of naturals.), though I'm not sure that's really necessary. When I've forgotten to do it there usually isn't any chaff left on the beans.

For light roasts I aim for around 14%-16% development and drop at the end of FC or slightly thereafter. I'll take it to 18%-20% for a medium roast.

Caveat: After a couple of years of roasting with the M3, I'm still learning and experimenting, but generally I'm getting good roasts.

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Cwilli62 (original poster)

#38: Post by Cwilli62 (original poster) »

Peppersass wrote:What size probes are you using and where are they placed? For reference to the description below, my probes are setup as described by erics. My MET probe is 1/16" placed between the drum and outer shell. My BT probe is also 1/6" to the right of the sight glass in the drop door. I have a 1/8" BT probe in the hole where the original analog thermometer was, as well as a 1/6" probe in the exhaust tube. I haven't found the information from those probes to be useful.

14g is close to the lower limit for the M3s. With a batch that small you'll have difficulty controlling the roast. I started out with 150g batches and eventually moved up to 175g to improve control. Not sure I'd go over 200g for fear of not getting enough heat into the beans to carry through the roast without tipping, scorching, raising MET too high, etc.

Typically, I charge in the 365F-385F range, with MET running about 480F-500F to keep the charge temp stable. I'm familiar with the idea of lowering the charge temp (e.g., by opening one of the doors), letting it rise and charging when it hits the target temp, but I haven't done that in a while. Instead, I wait until the TP, then increase MET. For example, if MET at charge is 480F, I'll bump it to 500F-520F at the TP. Then I don't touch heat until 1-2 minutes before FC, typically around the 90 second mark. Then I'll lower MET back to where it was at charge, say 480F.

I followed the EricS notes as well. I have 2, 18G probes and one 16G probe. The 18G in the original analog thermometer hole is what I am calling BT. The 18G probe above and to the left of the drop door is what I'm calling ET (I never really pay attention to this probe). And the 16G probe is between the drum and outer shell and I call this MET. So I think the positioning of the probes on the front are the same as yours, though the sizes may be different.

Your experience and advice are definitely helpful. From what you are saying, it sounds like you focus primarily on the MET to control/drive the roast. Is that correct? And you mainly use your BT probe to just double-check the charge temp.??



Everyone so far has been suggesting larger batches so I'll definitely try that out. I roast mostly naturals and like my coffee pretty light, as subjective as that can be. As equin0x points out, the BT at FC has been leveling out.

Using my past experience and collecting the information from everyone here, I'm trying to develop a baseline process. Once I can get decent roasts in general, I can hopefully use that baseline with new coffees and tweak from there. For such a simple little machine, it certainly is still tough to get things nailed down. Coffee roasting is indeed an art but I am trying to keep it a fun hobby! However, it is a lot more fun when the roasts don't taste like trash! Haha.

So far general ideas/advice are as follows:
  • larger batches
  • communicate in Watts instead of Amps
  • make sure that there is no restriction of airflow
  • make sure that charge temp. isn't too low
  • start lower with fan speed and increase over time
  • focus on between batch protocol
  • don't tinker with heat too close to FC

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Peppersass
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#39: Post by Peppersass »

Cwilli62 wrote: ...it sounds like you focus primarily on the MET to control/drive the roast. Is that correct? And you mainly use your BT probe to just double-check the charge temp.??
Not quite. I do use MET to control/drive the roast, but my use of the BT probe isn't limited to double-checking the charge temperature. It's much more important than that.

I use BT to mark the time to Dry End (DE), typically 300F, which is an important milestone for evaluating how fast the roast is progressing. Usually I aim for 4-minutes to DE, but for some fast roasts I've shot for 3-minutes. I've read recommendations that the time between DE and Brown (yellow gone, beans tan to brown) should be about 90 seconds, which I think tends to give you the right amount of time in Mailiard. I also use BT to get an idea of how close to first crack (FC) the roast is, which for many beans happens in the 360F-370F range. And BT is one indicator I use for when to drop.

Perhaps more important, the RoR curve is derived from the BT probe. I generally follow Rao's advice to aim for a gradually declining RoR, avoiding the crashes and spikes that can occur during FC. I like to see RoR at about 15-10 F/min when entering FC and not drop much below 7 F/min during FC.

Your description of your probes matches mine, except for the BT probe. You say that you have a 1/8" BT probe in the original analog thermometer hole. I have a 1/16" probe that goes through a hole in the screw immediately to the right of the round sight glass in the drop door. Consequently, it's quite a bit lower in the bean mass and it responds more quickly to temperature changes due to the thinner probe. Whether this makes a difference is open to debate. People who have switched from an 1/8" probe where yours is to the erics mod that puts it next to the sight glass can comment.

Cwilli62 (original poster)

#40: Post by Cwilli62 (original poster) »

Good thorough description. I certainly have some metrics to shoot for and some general best practices to keep in mind. I'll report back after several more roasts to see if I have success making positive changes.