A chart of the Popper roast chamber temperature and heat coil power based on the setting of the heat knob, as well as some new tips for roasting!
We have been working on mapping out how the position of the heat knob impacts the temperature in the Popper roast chamber.
This might seems straightforward, but it has been hard to relate the readings to the real world roasting experience. These temperature settings are based on running the roaster empty, and measuring the hot air as it enters the roast chamber. They are not the temperatures measured with coffee in the roast chamber.
Nonetheless, while we continue to improve on roast profileRoast Profile refers to the relationship between time and temperature in coffee roasting, with the endpoint being the "degree of roast". Roast profiling is the active manipulation of... ideas, with coffee in the roast chamber, it seems useful to share this information. The settings were done by an engineer at the factory and I corroborated the temperatures on multiple units here.
Two things to be aware of though. How you measure temperatures, and how a probe is placed matters greatly. That’s why I have been more interested in charting bean temperatures in roasting. But bean temperatures in an air roaster come with additional complications, because they vary by batch size, type of coffee, and how much a probe is actually reading a contact temperature with a bean versus the hot air stream.
The second surprise here is that in the final production unit of Popper, the roast setting between 2 and 3 isn’t meaningful! The power to the coil is the same. This was a surprise to me, even though I had tested the difference in prototypes. And I need to change our “initial roast recommendations” in the literature based on this. If you start at roast at 2, you might as well start it at 3, full heat! In fact, I now think it is best to roast initially at 1:30 on the heat dial (and fan on High … always start roasts on High fan speed!)
On the flip side, the fact that the heat dial has a “dead zone” between 2 and 3 is no shocker either. Any electric appliance with a digital or analog dial like this is going to have a lack of uniformity in the measured effect of incremental change. On an electric stovetop lets say, the difference between a setting of 4 and 5 will not correspond in temperature degrees to a change between 6 and 7. The reality is no control of this kind produces uniform results across the range. (And in fact a gas valve is no better, but at least you can “eyeball it” by looking at the flame!)
So please consider this chart as a starting point to better understanding the process when roasting with Popper!
| Popper Roaster | Low Fan Speed | Low Fan Speed | High Fan Speed | High Fan Speed |
| Heat Knob Position | Coil Power (W) | Temperature (F) | Coil Power (W) | Temperature (F) |
| 9:00 | 0 | 82.5 | 0 | 82.5 |
| 9:30 | 0 | 82.5 | 0 | 82.5 |
| 10:00 | 42.7 | 92.4 | 48.6 | 92.4 |
| 10:30 | 113.7 | 139.8 | 118 | 130 |
| 11:00 | 397 | 195.8 | 403 | 187 |
| 11:30 | 397 | 196 | 403 | 190.9 |
| 12:00 | 666 | 277 | 672 | 267 |
| 12:30 | 925 | 365 | 930 | 351 |
| 1:00 | 1098 | 436 | 1106 | 418 |
| 1:30 | 1096 | 445 | 1102 | 419 |
| 2:00 | 1173 | 465 | 1177 | 445 |
| 2:30 | 1173 | 465 | 1176 | 445 |
| 3:00 | 1173 | 462 | 1177 | 445 |
Popper Roast Profile Tips
Roasting with Popper means finding out what works for you … the machine doesn’t have programs or make roast decisions for you. (If you have one I am sure you know this already!) It’s a tool and of course, tools can be used in various ways. So it’s good to learn by experience, your own experience, but here are some general tips that supersede what comes with the printed material with the roaster:
- In our opinion, a good starting roast profile is 85 grams (weighed out), with Fan set to High and Heat set to about 1:30 on the dial (ie, 1:30 on a 12 hour clock face).
- Coffee should rotate initially, even if it is quite slow, and pick up speed in the first 30 seconds – 1 minute
- You might hear the start of First CrackFirst crack in one of two distinct heat-induced pyrolytic reactions in coffee. It is distinguished by a cracking or popping sound in the coffee, and occurs between 390... as early as 4 minutes into the roast (which would read 6:00 on the digital timer). But first crackAn audible popping sound heard during roasting. In coffee, one refers to "first crack" and "second crack," which come from two different classes of chemical reactions.: An audible... should be slow and extended at these settings. If it is rapid, reduce heat to 1:00 on the heat knob.
- In the middle or toward the end of first crack, reduce the temperature to 1:00 or 12:30 on the heat knob.
- You can finishSimilar to aftertaste, but it refers to the impression as the coffee leaves the palate. Aftertaste is the sensations gathered after the coffee has left the mouth. We... out the roast this way, or if you want further bean development, headed toward second crackAfter First Crack, a roast reaction around 440 to 450 degrees that is distinguished by a snapping sound. Second Crack is the second audible clue the roaster-operator receives..., change the Fan Speed knob to Low setting. This will increase the roast chamber temperature and help the roast develop more.
25 Responses
Is this an error?
“reduce the temperature to 1:00 or 12:30”
Thanks for the question … it isn’t a typo, but I know instructions can get confused because the way we refer to the heat knob settings as a clock face. So what it is saying is to start the roast at about 1:30 as if, when facing the roaster, the heat knob is a clock face with a range from 9:00 to 3:00 with 12:00 at the midway point. And depending on how the 1st crack is sounding, reduce the heat to a setting that would be 12:30 to 1:00 (again, heat know as a clock face) when you are hearing first crack. None of these are references to roast time
lets say i roast 5 batches of the same coffee,exactly the same , then let them rest. 24 hours later i brew 1 batch. can i expect to get a little bit different flavor on the next batch that will have been rested for 48 hours and 72 etc?
Hey Kevin,
Great question. The coffee will continue to off-gas CO2 during the period of rest between roast and brew, but I honesty wouldn’t expect a huge change in flavor between just a couple of days for most wet process coffees. We do recommend longer resting periods for some of the coffees with more outlier flavor profiles – Sumatra, dry process Brazil, etc – and that’s because there does seem to be a perceptible difference in flavor between day 1 and day 3, for example. The flavors seem to coalesce with the extra couple days rest, whereas they’re much more disparate straight from the roaster, and even at just 24 hours.
For me, part of the fun with these smaller batch size roasters is having that flexibility to taste different batches over time, or slightly different roast levels, etc, and get a better idea where the proverbial ‘sweet spot’ lies, or just to see if you do indeed taste any differences.
Hope that helps. Let me know if I can answer any other question!
-Dan
If I wanted a light roast, at what point should I initiate cooling mode in relation to first crack? At the start, middle, end? Thank you!
Hey Jim,
How soon you pull the batch after 1st crack is underway, will depend on how hot the roaster is. Generally speaking, stopping the roast toward the end of 1st crack should yield a lighter roast level (roughly City). If your Heat dial is at like 2:00 position, you are likely to hit 1st C within the first 4 minutes, and I’d look to start the cool cycle around 1:00 after the first audible snaps. I tend to keep my Heat settings around the 1:00 position, which gets me 1st Crack around 5 minutes, then pull my roast after 1:30 more.
Hope that helps. Feel free to reach out with any other questions.
-Dan
The Popper seems ready-built for an Arduino-based modification to control roast using a temperature probe. There is a 2.5mm pitch rectangular connector on the power control board to which the Arduino can be attached to drive the heater and fan triacs and have access to onboard 200mA 5VDC power. If you want to encourage this effort, you might consider publishing schematics as well as the make and model of that connector.
Otherwise, it seems like a firmware change to the Popper control board could make temperature control linear with respect to heater knob orientation. The usable range of that knob is currently very limited.
Thanks a lot for your thoughts on this James – I myself haven’t done the modification but am eager to … honestly I was hoping someone would share some insights on this or offer a guide. I think some new approaches coming from the home roasting community could really open up great possibilities for control of the Popper. I can look into publishing more info to assist with this, but have been dealing with some resistance from the factory engineers over transparency on this. I’ll keep at it though.
I am definitely interested to tune the heat knob function so it covers the useable range better!
An optical encoder would be better than the potentiometer
good tip – will need to research this
Roasted 100g at 1:30 with fan on high. Movement was slow but beans were circulating. However the roast did not complete and beans were half roasted as the heat shut off too soon and adding time had no effect. I am guessing the overheat mechanism triggered.
tried again with 90 grams same result. Seems like the overheat mechanism is faulty. Any ideas?
Hmm … this seems unusual. But yes it could definitely be an issue with the overtemperature switch. re-positioning it or bypassing it could be the cure. There’s a video focusing on it here:
https://www.youtube.com/watch?v=enEu0NmhkDU
Hi Thompson and all, first time roasting Popper on my granite countertops and the fan vibrations seem to be causing the temperature control to vibrate hotter pretty aggressively. Any tips to make the rheostats stiffer? About to try with some rubber shelf liner under the Popper.
Hi Nicky – this has not been an issue before, and I wonder if your machine has the 4 rubber footpads intact? It could be that the fan is out of balance. Have you used the machine in other locations successfully?
I’m about 10 batches in on my popper and have only been getting flat, dry tasting coffee. My last few roasts were 4 minutes at 750w then up to 950w till first crack(5:30 total time). Then about 1:30 development. Any recommendations?
I would consider going to opposite direction – initially roast at 950 watts and step down for a slower , more controlled first crack… it’s what I used on the Burundi I enjoyed this morning…
Looks like the heat setting potentiometer is not very precise. The wattage jumps quite a bit and I could never get somewhere around 950w. It jumps literally from 910 to 1050.
I understand this might be a budget limitation. If I want to upgrade that variable resistor for a more precise control – any suggestions what should I get?
Yes you are the second person to experience this jump from those approximate wattages. It is a variable resistor and the next production will have 7 stages vs 5. (But i definitely wish it was possible to not have these “steps” in wattage vs a smooth transition. It sounds like you know your stuff, but my understanding based on the technical details (from the UL report) is that the DC motor and AC fan restrict this. I have found, and probably you noticed that the wattage levels don’t trigger at exactly the same point in the know rotation when going clockwise vs counterclockwise. On the plus side it can help me find the wattage level I want to try both directions. Don’t think that helps your case but want to mention it. The other thing I wanted to see is if working with the line voltage can help ” fine tune” in a low tech way. 4000w motor controllers/thryisters have become really cheap. they aren’t great quality I am sure, but I have been using several versions on popcorn poppers with good result. I wanted to see how playing with line voltage a little on the Popper roaster might allow some tuning, in fact was going to try it here at home as I write this but found I didn’t have the wattmeter here with me. I’ll try it tommorrow though
Mine never worked right and once I got a power draw meter I found the cause. Defective rheostat so the power draw was either too little so the temperature was too low or it jumped to too hot. Nothing in between. Now past warranty but I am disappointed it never worked.
Sorry to hear this. There should be basically 6 heat levels. Its possible the adjustment was jumping past the most useful ones. Here was a table from a bench test, trying to correlate knob position to the wattage levels https://library.sweetmarias.com/popper-heat-settings-roast-temperatures-and-roast-profile-tips/
Quite possible to swap out the control board and the machine will function well. Are you interested in opening it up and switching the board out?
Hiya. I’ve been exploring the possibilities with this roaster for almost a year now. I’ve got a Wattsup device that I use in front of the popper, and have added the Phidgits bundle that breaks out 2 K-type thermocouple as detailed here in the Artisan site – https://artisan-scope.org/phidgets/2x-tc-set/ . Before that I was using the Wattsup with a single thermocouple and display meter that I bought here. I jusst started using Artisan.
My popper heat knob has nowhere near the control that is documented in the table near the top of this blog post. There’s a distinct jump from 700-ish watts to 1020 watts, with no ability to find a value in between. There are several other large ‘gaps’ between min and max.
Reading the dialog here and other SM Library articles there are some ideas offered on how to make this ‘roaster’ more controllable.
Has anyone implemented any of these ‘workarounds’ ? There’s mention of adding an in-line thrystor (Thompson), and getting the schematics from the board/electronics mfg. – did that ever happen?
‘J’ mentions adding an optical encoder would be the way to go.
James Robinson mentions “There is a 2.5mm pitch rectangular connector on the power control board to which the Arduino can be attached to drive the heater and fan triacs and have access to onboard 200mA 5VDC power…” – I’d love to know more, and take it further. I think if you went that far, might as well make heat and fan controllable in Artisan 😉
I think there are other mentions about the lack of fine control on this unit in some of the other library posts. Has any progress been made by anyone? Maybe I’m trying to take the capabilities of this roaster too far, but I think the lack of fine heat control is a shortcoming, and/or a defect that could be solved given the right skillset and information. Heck, I’d be happy for a procedure or just a replacement part recommendation that would work to swap out the crappy pot that’s there now with something that works better.
Thanks for any input and/or insight.
Hey Frank, thanks for the thorough explanation of what’s going on with your Popper. The first thing to address is the missing middle power step. Some of the steps are big, but there should definitely be one between the 700 – 1000 range, which is needed for practical roasting. It sounds like yours is missing for whatever reason, and we’ve only seen this in a couple other roasters. We’d be happy to send you a replacement board that functions correctly, where you can adjust and see the range between 700 and 1100 represented. There are still big steps where fine control is needed, which is why we augment it with the combination of the volt controller and watt meter.
As for the modifications that are mentioned in the thread, I’m going to pass those along to Tom and see if we can find out. He’s traveling at the moment, so it could be a couple days before one of us replies with more info.
On the replacement board, please shoot me an email and we’ll get you sorted out! [email protected]
Thanks again,
Dan
Am I reading the heat knob settings and corresponding wattage chart correctly? With the fan on high and the heat knob at the 1:30 position, the wattage is 1102, but at the lower 1:00 position the wattage is higher at 1106.
Hmm – well 1102 and 1106 watts is not a difference that is going to matter much. So from this is appears that the 1:00 and the 1:30 position on your popper are falling within the same wattage level “step”. You might need to be going outside of this – to 12:30 position to get the lower watt step, and to 2:00 to get to the higher step. The exact watt levels depend on a lot of things with the electric supply (age of home, distance from main panel …) .
Not sure this will read correctly in comments but here is a comparison of 2 watt checks I did at 122v on popper recently – but I used only :00 position settings
Popper Test 1 122 v Test 2 122v
9:00 47.1 47
10:00 212.5 214
11:00 439 435
12:00 718 714
13:00 962 953
14:00 1110 1101
15:00 1170 1167
My experience exactly is described by Donald in the November post above. Two settings anywhere near roast range –
one too low, the other way too high (1140 -1160), (have experimented with 80-130 grams) only an nth of a turn on the knob.
At 120v. I posted something to this effect in another thread, but these seems to be the more appropriate one.