Roasting Multiple Batches in the Popper Coffee Roaster (and Sample Roasting too)!

Popper coffee roaster with multiple roast batches
The Popper roaster after roasting 5 batches of coffee.

How to achieve consistent roast results from one roast batch to the next on the Popper coffee roaster.

This is our basic guide to roasting multiple batches of coffee in the Popper coffee roaster. Popper is a small-batch air roaster, capable of roasting up to 100 grams of green coffee at a time (roughly 3.5 ounces or 3/4 cup by volume). The small-ish capacity means you’ll likely find yourself roasting several rounds of coffee to cover your needs for the week (or even days). We’ve run hundreds of roast tests on these machines, and share our method of achieving consistent, back-to-back roasts here.

Roasting consecutive batches consistently is also one of the main requirements for sample roasting, and we take a look at how Popper stands up to that test as well, and whether or not it might function as a low-cost sample roaster for green coffee evaluation. (Scroll further down this page to see notes on sample roasting)

” Popper* is a coffee roaster” is modeled after the classic, high power popcorn poppers a lot of you learned to roast coffee on – like the West Bend Poppery II. What sets Popper apart is that it has fully adjustable heat and airflow settings, the ability to roast and cool coffee in the same chamber, and also a larger roast capacity. The manual controls are a big part of what separates this namesake from the poppers of yore, and what gives you the ability to roast continually in a controlled way.

If you’re already roasting back-to-back and happy with the results, you don’t necessarily need to change what you’re doing. But if you’re interested in hearing how we do it, or are at all curious how Popper withstands continual roasting, read on.

Consistent roasts require consistent roast changes

This probably goes without saying, but if you want to achieve consistent roast results, you have to be somewhat regimented in your roast process. Thankfully, Popper doesn’t require a whole lot of input or heat changes to keep things rolling smoothly, but we try to replicate any adjustments we make the best we can to minimize roast variance.

I had my heart set on finding a single heat setting that would achieve a 6 to 7 minute roast time overall, with a nice upward slope in temperature, and gentle first crack. I haven’t found that single setting yet. But what I did find, is that Popper’s Heat Dial settings are pretty touchy, and even minor adjustments can make a big impact on my roast curve. A hair too far in either direction can cause my roast to stall out, or send it rushing through 1st Crack VERY fast (3-4 minutes).

 Checking roast consistency of three Popper roasts on the cupping table, the crust tells you quite a bit, and the cup flavors even more!
Checking roast consistency of three Popper roasts on the cupping table, the height of the crust tells you quite a bit, and the cup flavors even more!

It took me quite a few roasts to figure out where the high and low set points are in relation to the paper dial I have glued above it. Once I did, I was able to find two heat settings to oscillate between in order to get that nice gentle roast slope.

Another finding was that Popper’s cooling cycle plays a pretty big role in roast predictability. If you only run a single cooling cycle between batches, it doesn’t cool the machine down all the way, leading to higher drop temps from one batch to the next, and ultimately faster roasts. But by running an extra cooling cycle without coffee in the roast chamber, you bring down Popper’s temperature much closer to where you started, ensuring the next batch starts at a similar drop temp.

Laying the groundwork for roasting multiple batches in the Popper

In order to accurately track the heat changes during the roasting process, we installed a rigid thermocouple to measure the temperature of the coffee, and air around it while it roasts. We did this by drilling a hole through the back of the roaster body on through to the roast chamber, aiming for just above the fan inlets so that the probe will sit within the bean bed during roasting.

The thermocouple we used (sold here) comes with a threaded nut to hold it in place, but we opted for drilling a hole the same diameter as the probe (3mm) so that it stays put on its own, without the nut. Please keep in mind, we are not recommending you modify your popper, and it will void your warranty!

We also affixed one of the paper dial gauges that’s included with the Popper directly over the power knob to more accurately pinpoint the dial settings. This simple upgrade allows you to translate your dial position into a numeric value, which helps immensely for tracking your path to the perfect roast. We also found it helpful to color in the slot on the knob with a bright colored paint so that the settings are easier to see, like we’ve done here.

OK, so onto the roasts. I settled on running 5 x 100 gram batches in a row, since that yields roughly 1 lb. of roasted coffee at a lighter roast level. For my initial test, I only ran 1 cooling cycle after the roast completed – as ‘back to back’ as the Popper can get without using an auxiliary cooling tray.

It became clear to me pretty quickly that the roaster never fully cooled back down to the initial ambient temperature. As the temperature of the roaster increased, the roast times got shorter. A little variance is no big deal, but a full minute difference from one roast batch to the next is not good if you’re shooting for consistency.

As I mentioned above, running a second cooling cycle addresses this issue, but it’s also good for the machine! Popper has a lot of plastic and aluminum parts, more of a kitchen appliance than a commercial roasting machine made that can be run all day and night. Treat it nicely and it will last a really long time. Abuse it, and it will not!

A sewing needle and yellow paint help spot the heat dial setting on the paper dial gauge included with the Popper, just be sure to put it on straight!
A sewing needle and yellow paint help spot the heat dial setting on the paper dial gauge included with the Popper, just be sure to put it on straight!

Check out our video tutorial on roasting multiple batches in the Popper, including a time-lapse comparison of 3 consecutive roasts…

Roasting Multiple Batches in Popper is a Coffee Roaster. Sample roasting too!

A general guide for back-to-back roasting

Keep in mind, this is what worked on my machine, with my ambient temperature, line voltage, coffee, and dial gauge placement. These factors will all differ to some degree from the variables you’re working with. The instructions below should get you close, but expect to tweak it a bit to find the Heat Dial settings that work for you.

  • Affix the Heat Dial guide paper that came with your roaster by cutting it out and linking up around the knob with the 12:00 position straight up. Remember, gluing on the guide is an imperfect science. Our 1:00 position could be a little different than yours, and you may need to adjust the Heat Level knob ever so slightly in either direction to match our results.
  • Stick with 90-100 grams of green coffee. 100 grams should be the max batch size period in Popper! I also roast with the dome top locked in position for these tests.
  • Set the Fan Speed dial to High, and Heat Level knob to around the 1:00 setting (1 hashmark below 1:00 on my roaster), then start your roast timer by turning the Time knob 1 click to the left so that 10:00 displays on the LED.
  • Look for yellowing around 2:00 into the roast, and temps around 315-330F (more or less)
  • The rate of temperature rise (“ROR”) should slow significantly around 4:00 into the roast cycle (6:00 on the LED). The temperature is likely around 350-380F, and the beans should be tan at this stage.
  • Increase the heat by turning the Heat Level knob clockwise by 1 hashmark, which should get the ROR progressing once again.
  • Allow the roast to advance into 1st Crack at this setting. The 1st Crack temps I’ve recorded are in the 410F – 425F range.
  • After about 20-30 seconds, I turn the Heat Level knob down (anti-clockwise) about 1/2 of a hashmark so that I can run through the 1st Crack stage without triggering the over temp cooling safety feature that kicks in at 465F.
  • I start the cooling cycle 1:30 later for a light City roast, or closer to 2:00 for City+. How quickly the coffee develops at this point will depend on how hot the roaster is. You may find yourself making micro-adjustments to the Heat Dial knob to initiate a holding pattern of sorts that keeps the roast from either taking off or stalling.
  • After the initial cooling batch is complete, dump your batch, empty the chaff basket, and run the cooling cycle once more without any coffee in the chamber in order to bring the roaster temperature down completely (around 90F).
  • In short, the benchmarks I look for after starting my roast are yellowing around 2:00 in – (8:00 on the LED – remember, it counts down!), tan/brown by the 4 minute mark (6:00 on the LED), and then cracking anywhere from 1 to 2 minutes more.
  • If the roast plateaus at any point before, turn the Heat Level knob clockwise a hair at a time until the temperature starts to advance again. It’s very easy to overshoot the mark, causing the roast to take off! Adjustments should be minuscule, and just enough to keep you from stalling.
  • Once you’ve found the proverbial ‘sweet spot’, you should be able to stick close to the same power setting for successive batches if you’re roasting the same coffee.
  • Now you’re ready to roast your next batch, simple as that!

Additional observations after running several consecutive roast tests

I’ve run several rounds of back-to-back roasts, and overall, found the Popper to roast fairly consistently once you identify the settings mentioned in our instructional. We’ve checked the consistency by cupping the coffees side by side, with no real perceptible differences in flavor. We’ve also measured the post-roast weight loss, which shows very tight range of 12% to 12.5%, not bad at all! (you can see this demonstrated in the video below as well with a different round of coffees)

Popper Coffee Roaster Chart of Heat Knob Settings and Corresponding Wattage and Temperature Rev 10/2021
Popper Coffee Roaster Chart of Heat Knob Settings and Corresponding Wattage and Temperature Rev 10/2021

Running multiple batches puts some strain on the Popper too, which is reason enough to run two cooling cycles between roasts (don’t skip this step!). You should limit continual roasting to 5ish roast batches for that same reason. It’s good hygiene for both the electronics and fan blower to give them break.

Also, don’t let chaff build up around the base of the machine. Popper’s fan intake is underneath the machine and can get clogged with coffee chaff, straining the fan function, and eventually frying the machine. Popper’s top does a good job of containing the chaff in the connected basket, so you shouldn’t have to worry about this too much if roast with it locked in place.

The Popper works as a sample roaster too, but there are a few things to consider

Throughout our tests we kept the question of whether or not the Popper would make a decent inexpensive sample roaster in mind. After using it ourselves for this very purpose, we can say that it most certainly will. But there are limitations to consider when deciding if it will work for you.

We think Popper is best suited for roasting a low volume of samples, so for either a smaller shop that doesn’t receive a lot of coffee samples, or as a backup for when you don’t want to fire up your larger sample roasting machine. Our Probat P3 uses a lot of power, and takes a half an hour-plus to warm up to roasting temp. Popper’s afforded us the flexibility of roasting a few samples immediately when we want to get to them quickly.

On the flip side, it isn’t suited for roasting 10’s of samples in a single session. Like I mentioned earlier, it’s a consumer grade roaster, and not made to withstand the abuse of a commercial machine.

And finally, there’s a real time bottleneck to consider. You can only roast one batch at a time on Popper, and need to allow for 6 full minutes of cooling in between batches. It takes me about an hour to roast 5 batches of coffee, which could be a deal breaker for some.

Popper can roast really small roast batches too. I’ve roasted as little as 50 grams of green coffee following the basic roasting guidelines listed above. Counter to what you might think, roasting such a small batch size helps slow the rate of rise as you near 1st Crack because the smaller bean mass is dispersed quite a bit, and allows hot air to pass by the coffee.

Other useful links to getting the most out of your Popper coffee roaster

Check out our Popper FAQ, with links to the manual, and our quick startup guide.

Roasting dark in the Popper isn’t difficult. Here’s our instructional on pushing through to second-crack.

Decode the Popper’s heat temp settings and how they correlate to the paper dial gauge.

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