Getting started with home roasting
What green coffee is, what you need for a first roast, where to do it, and how much coffee to buy.
Why roast at home
Green coffee is the seed of the coffee cherry after it's been processed and dried, before roasting. It keeps for months stored cool and dry, while roasted coffee is at its best for a few weeks. Roasting your own means coffee that's always days off roast, a much wider choice of lots, and a lower price per cup: green coffee typically costs well under half of what the same coffee costs roasted.
It's also easier than it sounds. A first roast takes about fifteen minutes with a popcorn popper or a pan, and the result is usually better than you'd expect.
What you need
Every method comes down to heat plus movement, so the beans brown evenly. You can start with things you may already have.
- A heat source
- A hot-air popcorn popper (the kind with side vents, not a mesh screen at the bottom), a heavy pan on the stove, a heat gun over a metal bowl, or a home coffee roaster. Poppers and pans are cheap and roast small batches; dedicated roasters cost more and give you control and bigger batches.
- Two metal colanders
- For cooling: pour the beans back and forth between them, or shake one, until the beans are cool to the touch. Outdoors this also blows off the chaff.
- A kitchen scale and a timer
- Weigh the green coffee going in, note when first crack starts and when you stop. That's all you need to repeat a roast you liked.
- Somewhere to roast
- See below: smoke and chaff decide where you can roast more than anything else.
Smoke, chaff and safety
Roasting makes smoke, a little at light roasts and a lot once you reach second crack. A strong range hood can handle light roasts in small batches; otherwise roast outside, in a garage with the door open, or next to an open window with a fan. Expect your smoke alarm to have an opinion the first time.
Chaff is the papery skin that comes off the bean as it roasts. Air roasters and poppers blow it out, so roast where a little flying chaff doesn't matter, or have a bowl or a chaff collector under the chute.
Never leave a roast unattended. Beans and chaff can catch fire, especially in poppers and at dark roasts, and many popper manuals warn against roasting coffee for that reason. Stay with it, keep the batch small, and unplug the popper when you're done.
Your first roast
Weigh out a small batch: around 70 to 100 g for a popper, enough to cover the bottom of a pan in a single layer. Heat, then add the beans and keep them moving.
Watch the color go from green to yellow (it smells like grass or hay), then tan and light brown (bread, toast). After a few minutes you'll hear first crack, a popping like popcorn. When it slows and stops, your coffee is at about City; a minute or so later it's City+ and then Full City. The roast scale explains each level and what it tastes like.
Stop a little before the level you want, since the beans keep roasting while hot, and cool them fast in the colanders. Let them rest at least overnight before you brew: fresh-roasted coffee gives off a lot of gas, and most coffees taste better after one to three days.
Choosing and buying your first coffees
Start with a forgiving coffee: a washed coffee from Brazil, Colombia, Guatemala or another Central American origin, with a recommended range that spans several levels ("City+ to Full City+"). They taste good across a wide window, so your first roasts don't have to be perfect. Leave naturals, decafs and very dense, light-roast-only lots like Kenyan AAs for later; they brown unevenly or need more careful heat. Washed coffees from these origins are a good place to look.
Buy a few pounds of two or three coffees rather than one big bag: you'll learn more from comparing. A pound of green makes roughly 13 ounces roasted, since the beans lose water as they roast, and green coffee keeps well for six months to a year in a cool, dry place.
Every coffee in the green catalog is priced per pound at its smallest real bag, so sellers with different bag sizes compare directly. Shipping often matters as much as the price per pound on small orders, so it pays to buy from one seller at a time.