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Home Roasting Coffee

 Words by Joanna Han & Photographs by Tec Petaja

With the right equipment and a little bit of experimentation, roasting coffee at home can be easier than baking bread or making popcorn. Coffee can be roasted on everything from a cast-iron skillet to a fancy sample roaster, but our machine of choice is a vintage air popcorn popper found at a thrift store for a few dollars. We asked home roaster and Kinfolk reader Thomas Putman to share his instructions.

How long have you been home-roasting coffee, and why did you start?
I started home-roasting coffee about four years ago—I was really just curious about the process and picked it up as a hobby. Over time, I’ve discovered that I like the idea of being self-sufficient—I like roasting coffee for the same reason I enjoy baking bread or making chicken stock from scratch. It’s also great that it’s economical. A bag of coffee from my favorite roaster in town is $22, which I can’t afford on a weekly basis!

Where do you get your green coffee?
I buy my green coffee from Sweet Maria’s in Oakland. They’re great—their website is incredibly informative and it’s a great resource for anything coffee-related. I buy from them in bulk to save on shipping, and I always look forward to picking out new coffees to try.

What are the downsides of roasting at home?
Obviously it’s going to be hard to get an even and accurate roast on a popcorn popper. Consistency is hard to achieve when you roast on such a small scale, and variables like ambient temperature can have a significant effect too. If money were no object, I’d love to get a 1 pound-capacity drum roaster—something that looks nice, like a San Franciscan. But for now, I’m happy with my trusty West Bend popper. I’ve had this thing for over four years and it’s still going strong.

What do you aim for the coffee to taste like when you roast?
Sometimes I try stopping batches just when it starts to even out after the first crack to get something juicer and tea-like — I love light roasts. But usually I like letting it go a little further, just enough to get some caramel-y notes, too. I like getting a bag of coffee from my favorite roasters then ordering green beans from the same region or farm from Sweet Maria’s. It’s fun to see how the home roast compares to the professional roast—honestly, the home roast often tastes just as good.

Any other tips for the beginner home roaster?
Really, just throw some coffee in the popper and get excited about the fact that you’re roasting. You can make it a more scientific process by taking notes and recording weight and temperature if you want. It’s really important to learn how to taste coffee, too, rather than just drinking it passively with breakfast in the morning. You’ll start to appreciate good coffee a lot more.

Air popper with side vents
80 grams (about 1/2 cup) green coffee beans
Bowl or sink basin
Window or fan for ventilation
Scale or measuring cup
2 metal or mesh colanders, preferably with handles
Paper and pen for note-taking

1. Set the popper up in a ventilated space with the bowl or sink basin in front of it to catch the chafe, the papery “skin” of the beans.

2. Turn the popper on and let it warm up; this helps with consistency when you’re roasting multiple batches and allows the coffee to roast more evenly.

3. While the popper is warming, weigh out 80 grams (about 1/2 cup) of green beans. If you plan to roast multiple batches, weigh out all the coffee before you start.

4. Start the stopwatch and pour the beans in the popper, giving it a gentle shake to encourage the beans to start spinning, then secure the lid. Pay attention to the changing aroma of the coffee as it begins to roast.

5. At around 2 minutes (it could be earlier or later depending on your machine), you’ll hear what sounds like popcorn popping—this is the “first crack” and is your signal to start paying close attention. Use oven mitts to remove the lid, and inspect the color of the beans. You can compare it to coffee roasted by your favorite roaster to use as a guide, but ultimately the roast level is up to you. If you let it continue roasting after this first crack, you’ll eventually hear a “second crack”—a sharper series of crackling sounds—which means you’re headed to a darker roast.

6. Once you’ve reached your desired roast level, quickly turn the machine off and carefully transfer the beans to a colander. Swirl it and transfer it back and forth between two colanders to help it cool down and stop the roasting process.

7. Once it’s completely cool, store the beans in a cool dark place in an airtight container.

Other Tips
• Roasting usually takes about 3–4 minutes a batch, but the time will vary depending on the machine and other variables. You can use a thermometer to keep track of the temperature (in a warmer environment, the coffee will roast more quickly). Also consider weighing the coffee before and after roasting to calculate the percentage of weight (moisture) lost.

• Home Roasters is a helpful website with lots of tips for ways to modify machines if you really want to be serious about it.

• Remember not to simply put on a timer and stop after 4 minutes. The best way to roast good coffee using an air popper is by keeping a close eye on the color and noting the changes in aroma.

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