How To Roast Coffee Beans

raw and roasted coffee beans

The Spruce / Pete Scherer 

Roasting your own coffee is economical, fun, and easy to learn.  While this quick-start guide doesn't cover every detail, it does provide a concise overview of the most important points. Coffee roasting is an art, rooted in the senses. Ultimately, you must pay attention to the sights, sounds, smells, tastes, and tactile sensations of the roasting process so that you can connect them to the results in your cup. Your creative engagement will drive your exploration, and you'll be sure to have more than a few great cups of coffee along the way. To begin, of course, you need some coffee beans. Start with an Internet search for "buy green coffee." You will find much to choose from, but don't agonize. Simply begin at the beginning, and buy one that sounds interesting.

Once you've got some green coffee, you must decide how to roast it. Some advice: begin humbly. Get your hands a little dirty and find out if this hobby is for you before you drop cash on a machine. To roast coffee, all you really need is a source of heat, somewhere between 350 and 500 F. Many people have gotten creative here, and you can too. Stovetop, oven, grill, open fire, heat gun, electric popcorn popper, or hand-cranked Whirly Pop, folks have devised roasting methods for them all. Why not start with your stove and frying pan? You can always buy a machine later. If you must buy something, consider the lowliest machine: the electric air popper. Lots of people start there because they are cheap, don't require much effort, and get good results. Although air poppers can be messy and can't fit much coffee, with starter bundles like this on the market, an air popper is hard to beat. If money is no object, on the other hand, buy this.

So, you've got supplies; now make a plan. What should your roasted coffee be like? To answer this, you must understand the roasting timeline. In order to talk about the timeline, the coffee world has developed its own special jargon. Knowing this lingo is not at all necessary for roasting great coffee, but it does enable you to understand and follow the recommendations of purveyors and fellow roasters. It goes like this. You've started your roast and the beans are heating. The first point of interest you will encounter along the timeline is called "first crack." You will know it by the popping or snapping sound you hear. Visually, the beans will have expanded somewhat, their color will be a matte light brown, and they may smell like malt or baking bread, often with aroma top notes like fruit, flowers, or herbs. This point is significant because it's here that the coffee starts to be drinkable. In coffee lingo, this roast level is called "city," and, with more time, "city plus."

The second significant moment in the timeline is called "second crack." When second crack begins, the roast is called "full city." The sound of second crack begins softly but becomes progressively more violent as the roast goes on. The beans have expanded further, sport a consistent medium-brown color with less matte, more shine, and aromas of chocolate and toast. Further down the timeline, second crack becomes louder. The beans will appear dark brown with an oily sheen, and the aromas will be deeply dark and roasted. There may be some light smoke. This zone is called Vienna, and later French. French is the last stop on the timeline, and the beginning of the end of drinkability. Some beans might taste better dark, while some might be best when lightly roasted. That's all part of the fun. In the end, the right roast is the one that tastes best to you. If you're not sure what to aim for, try to master the city roast before going much darker. Stop the roast a short time after you hear first crack, and you'll be fine.

Now that you understand the timeline, here are a few basic tips for navigating it. Professional roasting gets pretty technical, but there are two simple guidelines that home roasters can use for good results. First, keep the coffee moving while it roasts. You can do this by hand—shaking your pan or cranking a whirly pop—or by machine. Either way, moving the beans means even heating and a consistent roast. The second guideline is based on some deep empirical research in the roasting community, and also concerns heat. In a nutshell, you want to heat the beans quickly at first, then more slowly as time goes on. In practice, that means to preheat your roaster before adding the beans, then lower the heat a little at the moment of first crack. Finally, you should know that roasting can be messy. Green coffee beans shed a paper-thin skin, called chaff, that can blow around your kitchen. Also, roasting coffee can produce smoke. Higher-end roasting machines account for this, but DIY roasters may want to roast in the backyard.

When you stop the roast, it's time to cool the beans. Move them away from the heat and from each other, and give them plenty of airflow. You can toss small batches in a colander, and spread bigger batches out on sheet pans. Try to cool the beans to room temperature within three to five minutes. You may want to use a fan. When they are cool, store the beans at room temperature—never in the refrigerator or freezer—and away from light and air, which destroy flavor and aroma. Wait at least twenty-four hours before brewing. During this rest period, the coffee will release carbon dioxide which otherwise would interfere with flavor extraction during brewing. For peak flavor, use your freshly roasted coffee within two to seven days. Now good luck, and happy roasting.