Roasting Green Coffee 101
We know that life with coffee is good and life without coffee is bad. But beyond those basic facts, what makes coffee coffee is a total mystery to most of us.
Today, however, we’re revealing the rich, complex, and interesting side of coffee.
By roasting our own.
We’ll get into the specific tools needed later on, but as long as you have a gas grill or a portable burner, a cast iron skillet, and about 30 spare minutes, you’re ready to start roasting.
Where to Buy Green Coffee Beans
Depending on where you live, green coffee beans may be purchased from your local coffee roasting company. Do a web search for coffee roasters nearby and call to ask if they’d consider selling some of their inventory. Chances are, they’ve been asked before and will gladly part with a pound or two.
If you can’t find green coffee within driving distance, the internet has your back — as long as you buy from a reputable source like Sweet Maria’s (sweetmarias.com) or Bodhi Leaf Coffee Traders (bodhileafcoffee.com).
Primos Coffee also makes green coffee beans that many people say are amazing. Check with Amazon for pricing.
All three companies source their beans directly from the farmers and coops in the countries of origin to offer what is truly some of the best specialty-grade coffee in the world.
Making Sense of Green Coffee Lingo
The “spec sheet” of a green coffee reveals exactly where on the planet that coffee grew including the country, region within the country, the farm and farmer who grew it, the elevation of the farm, and other interesting facts about the surrounding terrain and climate.
Information about the varietal of the coffee — bourbon, typica, caturra, etc. — is also typically provided (if known) along with how the coffee was processed — wet, dry, or pulp-natural.
To the seasoned coffee roaster, all this background information tells the backstory of a specific coffee and provides clues for how it might taste. When you’re just starting out, however, don’t spend too much time comparing minute details between different green coffees you’re considering.
Simply read through the tasting notes provided by the retailer and go with the coffee you find most appealing. The roasting process remains more or less the same regardless of the type of coffee you’re roasting so you really can’t lose.
Understanding the Roasting Process and Why You Need to Roast Coffee in the First Place
Everything that makes brewed coffee so wonderful — the flavors, the aromas, the caffeine — are almost entirely unavailable in the bean’s raw state. But by applying heat to the beans during the roasting process, coffee’s most prized chemical compounds and solubles become available for extraction through brewing.
On average, it takes anywhere from 7 to 15 minutes to roast a batch of coffee. During that time, the raw coffee beans change from green to brown with a few distinct stages along the way. By understanding what’s happening during each stage, you’re able to make the changes and adjustments needed to yield the most delicious tasting roasted coffee possible.
Here is a rough breakdown of the coffee roasting process and its progressive stages:
Initial heating and drying (1 to 3 minutes): As soon as the green coffee beans come into contact with the heat source they begin absorbing heat. When the internal temperature of the beans rises, moisture within the beans starts evaporating as steam, producing the aroma of warm, wet hay. During this stage, the coffee remains its natural green color for the first few minutes.
Yellow (3 to 5 minutes): Once the coffee beans have dried significantly, they gradually change from green to a tan-ish yellow color. The aroma changes from wet hay to that of baking bread. You’ll also start noticing small pieces of chaff separating from the coffee and blowing off — yes, it gets everywhere.
Brown (5 to 8 minutes): When all the moisture has been roasted out, the beans turn from yellow to a proper brown and start looking like coffee as we generally know it. The beans will have increased in size slightly at this point, but will still be small and hard compared to the fully roasted beans. More chaff will separate and disperse across your workspace.
First Crack (7 to 12 minutes): During the drying, yellow, and brown phases, the coffee beans are endothermic, meaning they’re absorbing heat. Once the beans have absorbed the maximum amount of heat, they change from endothermic to exothermic and start releasing heat.
This transition is known as “first crack” because an audible “popping” sound is produced when gasses trapped within the beans rapidly expand, fracturing the bean’s physical structure. During this process, the beans begin producing substantial smoke and still more chaff.
It generally takes anywhere from one to three minutes for all the beans in the batch to undergo first crack. As soon as first crack concludes, the beans will be at a light roast level and brew-able for the first time.
If you enjoy crisp, clean flavor profiles that allow you to taste the natural notes of the coffee, end the roast here. If you like more body and boldness to your brew, keep roasting a few more minutes until second crack.
Second Crack (12 to 16 minutes): After first crack wraps up, there’s a brief period of silence. During this time, the beans continue getting darker as they move into the medium roast territory. Then, after anywhere from 10 to 90 seconds, another exothermic event known as “second crack” occurs.
You’ll hear another round of audible popping noises, but this time slightly softer and shorter lasting. If you end the roast as soon as second crack gets going, you’ll have a fully developed medium roast which is always a crowd-pleaser. Letting the beans roast through second crack and beyond will produce an ever-darker roast until the beans ultimately burn.
Knowing when to end the roast is everything.
Tools for Coffee Roasting at Home
First, start by making sure you have an adequate outdoor space for roasting. A substantial amount of smoke can be created so proper ventilation is essential. And of course, keep a fire extinguisher nearby just in case.
Then, round up the following items:
- Gas Burner — Many gas barbeque grills have side burners that are ideal for roasting coffee. If your grill isn’t equipped with a side burner, the cast iron skillet can be placed directly on the main grilling surface, assuming your grill puts off enough BTU’s. Portable gas burners or camp stoves — either propane or butane — work great for roasting coffee and electric hotplates can be used in a pinch, although many are underpowered and not ideal for the application.
- Cast iron skillet — Cast iron distributes heat very evenly which is important when creating an even and consistent roast. You can roast in the same cast iron skillet you use to cook your bacon and eggs, just make sure to clean and dry it thoroughly before roasting coffee — coffee is quick to absorb outside aromas, and if you aren’t careful, you’ll end up with a breakfast-flavored brew. See Amazon for options.
- Wooden spoon — Stirring constantly is another key to successful cast iron skillet coffee roasting. A standard wooden spoon or spatula is the tool of choice.
- Cookie Sheet — When the beans are done roasting you need somewhere for them to cool. Standard cookie sheets work great, and if you happen to have a perforated sheet or metal colander with mesh or small holes, that’s even better.
- Oven mitt, hot pad, or towel — Used for handling the cast iron skillet when hot.
- Measuring cup or scale — You can simply drop a handful of beans into the pan and start roasting with good results. But if you want to be more precise and be better able to repeat your roasts, measuring your beans is critical. Measuring cups work great but digital kitchen scales are more accurate — use what you have.
- Timer or Stopwatch — When striving for consistent roasts from batch to batch, tracking the progress on the clock is extremely helpful. Digital timers with large numbers make tracking roast times easy at a glance, but the timer on your smartphone is always a convenient option.
- Fan or fan-like object — After the beans roast they need to be cooled quickly, either by hand with a fan-like object (a magazine or small cutting board works well) or with a box fan.
Time to Roast: DIY Coffee Roasting Step by Step
Before you dive into the procedure, commit to staying with your pan of roasting coffee from start to finish. The coffee must be stirred continuously and if you walk away for even a few seconds, the beans will scorch producing unfavorable burnt flavors. Make sure you have all the necessary tools compiled and ready for action because once you start roasting, you must stay glued to the task.
Step 1: Preheat Cast Iron Skillet
Ignite your gas burner and set the flame to high. Place your cast iron skillet on the burner and let it heat up for 2 or 3 minutes. You’ll know the skillet is hot enough when you sprinkle water and it dances across the surface, boiling off immediately.
Step 2: Measure or Weigh Out Green Coffee Beans
While the skillet is preheating, measure out the beans you’re about to roast. Ideally, you want enough beans to cover the entire bottom of the skillet in roughly a half-inch thick layer. For a standard 8-inch cast iron skillet, 1 full cup of beans (roughly 185 grams on the scale) is just about right.
Step 3: Add Beans to Pan, Start Stopwatch & Stir!
Once the skillet has preheated fully, reduce the flame to low and wait 30 seconds or so for the skillet’s temperature to drop slightly. If the skillet is too hot upon starting the roast, there’s a chance the green beans will scorch.
Then, pour the beans into the pan, start the stopwatch, and start stirring immediately. Remember: Once the roast starts you can’t stop stirring!
Your goal is to move every bean in the skillet with every pass of your wooden spoon. Experiment with different stirring patterns — try circles, spirals, zigzags, or a combination — until you fall into a nice rhythm. It’s also extremely helpful to keep a grip on the skillet using an oven mitt or towel so you can shuffle the skillet every few seconds to keep the beans well agitated.
Step 4: Monitor the Roast and Adjust the Heat as Needed
You should start smelling the aroma rising from the beans as soon as they start heating. With the roast in full swing, your aim is to use your senses to monitor the roast and make heat adjustments as needed. Initially, your main concern will be to watch for any signs of scorching which will appear as small brown splotches on the outside surfaces of the beans.
At the first suspicion of scorching, lower the flame immediately and consider lifting the skillet away from the flame momentarily. Make a small flame adjustment then wait 20 seconds or so for the temperature change to take effect. You’ll need to continue making adjustments in this way throughout the duration of the roast, and with practice, it becomes very intuitive.
During the initial drying and yellow stages, the flame can be kept relatively low. As the beans start turning brown, however, more heat is needed to build the momentum necessary to carry the beans through first crack and beyond.
Whatever you do, don’t stop stirring.
Step 5: Moving Through First Crack
Somewhere around the 5 or 6-minute mark, you may hear the initial few pops of first crack. But don’t be surprised if the full onslaught of first crack doesn’t kick in until a few minutes later. There always seems to be a few early-bird cracks that sneak in.
In terms of brew-ability, the beans are ready to be ground and brewed anytime after first crack. From there, the beans will continue to darken until they’re incinerated. If you are a dark roast fan, don’t let the roast go too far past second crack — at that point, you’re riding a fine line between full-bodied dark roast and charcoal.
Roasting coffee in a cast iron skillet practically forces you to stick to very small batches. While it may take 3 or 4 batches to produce a pound of roasted coffee, each batch offers a new opportunity for experimentation and learning. Keep this in mind and try roasting your coffee in as many different ways as possible — end one roast very early just after first crack for a Scandinavian-style light roast and end the next batch much later to produce a classic bold dark roast.
Keep stirring and continue increasing the flame little by little until first crack is fully underway. When you start hearing steady pops — it’ll sound like popcorn in a microwave — lower the heat slightly.
Ideally, you want to have enough heat to continue moving the roast forward but not so much that the roast “runs away from you” and burns the beans.
Step 6: Deciding When to End the Roast
Ending the roast is as simple as dumping the beans onto a cookie sheet or into a colander. But what’s difficult is knowing exactly when to cut the gas and eject the beans.
7. Cooling the Beans
You haven’t stopped stirring, have you? Good. Once the beans have reached your desired roast level and color, simply turn off the burner and use your oven mitt to empty the beans out of the cast iron skillet onto the cookie sheet or colander.
Use your wooden spoon to spread the beans across the cookie sheet, then use a magazine or something similar to fan the beans and aid cooling. If you’re using a colander, shake and/or stir the beans until they are cool to the touch. If you plan on roasting several consecutive batches of coffee in one session, or happen to be roasting in hot weather, it can be a huge help to set up a box fan to accelerate bean cooling drastically.
Brewing and Storing Your Home-Roasted Coffee
Once your coffee beans have cooled to room temperature, they’re ready to be ground, brewed, and sipped. Any beans you don’t brew in one sitting should be stored in an airtight container and kept out of direct sunlight.
Try to keep the beans whole until just before brewing and keep them out of the freezer.
Because of the gasses in the fresh-roasted coffee, you may notice that the very first batch you brew is very bright, sour, or otherwise just “off.” Don’t throw it out just yet. Give it a day or two to let the coffee “de-gas,” as they say, before trying it again.
You’ll likely find that after a few days of rest the coffee is smoother, more balanced, and overall more enjoyable, just as every cup of coffee should be.
Thanks for stopping by!