How to Roast Coffee in a Whirley Pop Popcorn Maker


Of all the nutty kitchen projects at the Root Simple compound, by far the simplest and most rewarding has been home coffee roasting. Why more people don’t roast their own is one of the great mysteries of home economics. I learned how to do it at a workshop put on by the Institute of Domestic Technology, but, with a little trial and error, you can figure it out on your own.

A hand-cranked wood stove top coffee roaster circa 1890-1910. Image: Wikipedia.

A hand-cranked wood stove top coffee roaster circa 1890-1910. Image: Wikipedia.

The History of Home Roasting
Up until the 20th century if you wanted coffee you had to roast it yourself. Folgers, did not exist yet. But by the end of WWII, the Man deemed that all of us should drink crappy, stale, industrialized brown swill, so along with Wonder Bread and Twinkies, we got bad canned coffee and folks forgot how to roast. Then, sometime in the 1990s, the Man gave us Starbucks and demanded that we go into debt drinking slightly better coffee. It’s time to rediscover home roasting.

Why Roast Your Own Coffee?
The main reason to roast your own is that coffee, once roasted, goes stale within a week. With your Whirley Pop you can roast just what you need for a week. Another reason is that you can get really high quality, fair trade green beans for half the price of roasted coffee. And, since you are doing the roasting you can control the flavor exactly to your liking.

Choosing a Method
There are four general ways to roast coffee: drum roasters, hot air popcorn poppers, stove-top popcorn poppers and just a plain skillet. Each method has pluses and minuses. I’ve tried hot air popcorn poppers and stove-top popcorn poppers (such as the Whirley-Pop pictured at the top of this post). Between the air popper and the stove-top popper, I prefer the stove-top popper because you have more control over the roast and the device itself is inexpensive and suited to this use. The air poppers, on the other hand, tend burn out quickly when used for coffee roasting. I’ve never tried roasting in just a skillet (a traditional method in Ethiopia, by the way) and I’ve never sprung for a drum roaster due to the expense and lack of counter space in our kitchen. The stove-top popper seems to me a good compromise between expense and control of the roast. The folks behind the Whirley Pop make a more durable stove-top popper that I might switch to if I have to replace my current popper.

Fitting a Whirley Pop With a Thermometer
For years I’ve used a plain old unmodified Whirley Pop with excellent results. But recently I drilled a hole in the top and fitted it with a short, pocket-sized candy thermometer so that I can follow the progress of the roast through temperature readings. I’ll do a post about how to install a thermometer in the future, but until that time, you can look at these directions on the Sweet Maria’s website.

Whirley Pop Coffee Roasting Procedure
Roasting coffee is pretty straightforward and is basically all about adjusting the heat on your burner so that you don’t either roast the beans too quickly or too slowly. It takes a few times to get the hang of it, and while installing a thermometer in your popper will definitely help, you can certainly do it without the thermometer–it will just take a little more practice to get the timing right. The following directions are based on the ones in Kenneth Davids’ book Home Coffee Roasting. One big-ass caveat: your results may vary depending on your stove. These directions work on our O’Keefe and Merritt with a diffuser over the burner. An electric stove or a professional stove will work but will be different. I just tested this recipe on a portable butane burner and got better results with these slightly different directions from Sweet Maria’s. The caveat out the way, here’s how I roast coffee:

  1. Set a gas stove burner on low or your electric stove on medium and pre-heat the Whirley Pop for a minute or two. On our old gas stove, I use a medium burner setting and a heat diffuser. While the Whirley Pop is pre-heating, make sure you’ve got a colander at arm’s length and ready to dump the beans in when they are done roasting. Pre-heat the Whirley Pop, regulating the burner so that the temperature steadies at 475°-500°F (246°-260°C) and then put the beans in. If you don’t have a thermometer, pre-heating will be a matter of guesswork, most likely a few minutes at a low burner setting. Take notes each time you roast, and you’ll get a good system down soon, even without a thermometer.
  2. Add no more than 8 ounces/226 grams–by weight–of beans to the popper. If you use more than that and the beans won’t roast evenly. You could add less and roast more often for fresher coffee but I’m too lazy for this.
  3. Start turning the crank. For the first few minutes nothing much will happen other than you standing around turning the crank. You have to crank continuously or the beans will roast unevenly. Occasionally reverse directions for a second to un-stick any beans that get caught under the stirring mechanism.
  4. Watch the temperature. If it dips below 325°F/162°C, adjust the burner. Your goal is to hit and maintain a temperature of 350° to 375° F (176°-190° C). Note that the temperature of the beans will actually be much higher since they are in contact with the bottom of the Whirley Pop. If you don’t have a thermometer this will be a matter of trial and error as well as paying attention to the browning of the beans and the smell of the roast.
  5. Several minutes into the roast the beans will begin to turn light brown. Your first major milepost is “first crack,” the moment when they start popping like popcorn (though not quite as loud). This will be likely be around the 9 minute mark.
  6. You could stop at first crack for a very light roast, but most people keep going, shooting for a darker roast. After first crack, start paying very close attention to the smell and color of the beans. If you keep roasting, around the 12 minute mark you’ll reach second crack, which is lower in volume and sounds like crinkling cellophane. When to dump the beans out of the roaster depends on what kind of roast you are shooting for. Keep reading.

When to pull the beans
Don’t become a slave to the thermometer. Your thermometer is just a guide to get you started. More important is to use your ears to listen for the crack of the beans, your noise to smell the smoke and your eyes to judge the color of the beans. After several attempts you’ll get a good idea for where you should set your burner. Some roasting aficionados will mark their stove knobs with a Sharpie to pinpoint the ideal setting.

For a very light roast (too light, for my taste): Pull the beans in the middle of the first crack.

For a medium breakfast type roast: Pull when the first crack has ended but before the second crack begins. The beans will be a medium-brown.

For a “full city” roast: Pull just as the second crack begins. Beans will be starting to really smoke at this point.

For a dark roast: Pull in the middle of the second crack when the smoke starts to get pungent. The beans will be dark brown.

For a French roast: pull as the second crack reaches its peak. Beans will be very dark and shiny.

Cooling the beans and removing chaff
As soon as you finish roasting you need to cool the beans down as quickly as possible. Pour them into a metal colander or bowl. I take them outside at this point and pour them repeatedly between a colander and a metal bowl. The chafe will drift away in the process You don’t have to remove all of the chaff, so don’t get to obsessive about it. Note: decaffeinated beans do not have chaff.

Storing beans
Put your roasted beans into a lidded container but don’t put the lid on too tight. The beans outgas a lot of CO2 for the first 12 hours and continue to put off CO2 for a few weeks. CO2 is your friend. It pushes out the oxygen that makes beans go stale. This is why you should get an inexpensive coffee container with a valve. Roasted beans keep for around six days before starting to lose flavor.

Store your green beans at room temperature, away from sunlight. They keep very well in their green state. The clock only starts ticking after you’ve roasted them.

What can go wrong
Not much can go wrong other than having the burner too high or too low or pulling the beans too soon or too late. After you roast a few times you’ll get a good idea about how high to set your burner and roughly how long it takes for the particular style of roast you like. I would say that my most common mistake has been to pull the beans too early leading to a grassy and more sour taste.

When I first started roasting coffee I was surprised at the diversity of beans available. Some are tiny and some are large. This will effect the length of the roast. If you’re the note taking type, I tip my hat to you. Notes will help you will get more consistent results.

Roasting is a smokey process and will set off your smoke alarms. I do my roasting inside but shut the door to the kitchen to prevent the smoke alarms throughout the house from going off. Some people do their roasting outside on the side burner of a barbecue.

Where to Get Green Coffee Beans
I’m a big fan of Oakland, California based Sweet Maria’s Coffee. They carefully source their coffee and have very reasonable prices even including shipping. You can also ask your local coffee roaster if they will sell you green beans.

I shot a video of how I roast coffee that I will post as soon as I can make some time for editing. For Angelinos, I’ll also note that Kelly and I will be doing a coffee roasting demo at the Natural History Museum this Friday July 8th. That’s tonight, so we hope to see you later!

Now get roasting!









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  1. I have never used a coffeemaker or made a cup of coffee and only had two cups in my life. I gagged those down–needed to stay awake in one case and had a headache the other time. However, I am intrigued with your coffee roasting and all the information and specifics.

  2. Cool, I had the old aluminum one for years until the little gears wore out, I have been using the ‘Sweet-N-Easy’ stainless steel stove top popper to roast my coffee for a couple of years with much better and consistent results, not only is it stainless but it’s got a heavy bottom for better heat distribution and retention and the mixer is on top and direct drive so there are no gears to wear out. Love home roasted coffee, better taste, custom roast and way more affordable than even the bulk bins at the health food stores!

    • As soon as mine wears out I’m going to get a Sweet-N-Easy. The Whirley Pop is really flimsy.

  3. By the way what do you use to brew your coffee? I have tried just about everything, regular espresso maker, stove top espresso maker, all glass pyrex stove top percolator, French Press, Aero Press, I am now on to the Chemex, I think that it may be the best yet, as far as the true expression of the coffee flavor, I don’t like the paper filter use, but they go in the compost, there is a gold reusable one available, but the maker doesn’t recommend it, might try it and see. Mmmmmmmm, coffee!

    • I’d love to try a Chemex someday. Right now I use a metal French Press and I’m pretty happy with the results.

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