Yes, it really IS possible to roast coffee beans using a hot air popcorn popper! Though of course the machine will be useless for anything but coffee afterwards due to the oils the coffee will deposit, but…ah, the aroma!!! Coffee roasting is truly something everyone should experience, and if you have an old air popper sitting around, why not give it a try? There’s a pretty good writeup over at BaconPress, and you can find the green (ie, unroasted) coffee beans online at Sweet Maria’s. Sweet Maria’s also has instructions for roasting coffee with a popcorn popper, which you can find here or copied in the extended version of this post.
The instructions below were copied from Sweet Maria’s, the world’s best resource for buying green beans! This isn’t the best way to roast coffee, but it’ll still be better than store-bought beans.
Set up the popper in a ventilated place near a kitchen exhaust fan or window, if possible. It’s nice to have strong overhead light so you can look down into the popper chamber to accurately judge the roast as it progresses. Have all your supplies within reach. Put the same amount of coffee in the popper that the manufacturer recommends for popcorn. For the West Bend Poppery II, 4 oz. is the maximum, or 2/3 to 3/4 cup.
Put the plastic hood (including butter dish) in place, and a large bowl under the chute. We put our popper by the sink so it blows chaff right into the basin. Turn the thing on.
Watch for fragrant smoke and the “first crack” of the beans in about 3 minutes. Wait another minute, then start to monitor beans closely for desired roast color by lifting out butter dish and looking into popping chamber, or, better yet, by smelling the smoke and listening to the crackling. Total time for a lighter roast should be around 4 minutes, full city roast around 5, and darker roasts closer to 6.5 minutes. Roasts develop quickly, so be vigilant. You want to pour the beans out of the popper when they are a tad lighter than the color you desire, since roasting continues until beans are cool. Agitate beans in metal collander with a big spoon or toss between 2 collanders until they are warm to your touch. You may need oven mitts for this. You may want to walk out to a porch to aid cooling. Coffee should be stored out of direct light (and not in a fridge or freezer) in an airtight glass jar, but with a fresh roast, wait 12 hours to seal the jar tightly; it needs to vent off C02. Warm, fresh roasted beans are wonderful, but the coffee attains its peak 4 to 24 hours after roasting. If you store it as recommended, we’ll call it fresh for 5 days. When you open that jar in the morning, you will know what fresh coffee truly is.