coffee roaster roasting coffee beans with a commercial coffee roaster

Coffee Roasting: How to Roast Coffee Beans at Home Efficiently

The only thing better than a hot cup of coffee is a coffee made from freshly roasted beans. Although the roasting process can take some time, I love the satisfaction of sipping my own brand of coffee.

If you’re a diehard coffee lover, you might want to learn how to roast coffee beans at home. You can tweak your coffee roasting techniques to create your own perfect cup of coffee.

Coffee in Its Natural Form

Of course, before I teach you how to roast coffee beans at home, we need to talk about the source: the coffee tree. Without their usual trimming, a coffee tree can grow to be thirty feet tall and has many waxy green leaves.   

a hand holding a bunch of coffee cherries

You might be surprised by a coffee bean’s appearance before it’s processed. Once it’s three or four years old, a coffee tree produces cherries every year, which turn bright red when they are ripe. Once a year (except in Columbia, where trees flower twice a year), workers pick the ripened cherries.

Processing and Drying

Next, the cherries must be processed quickly, before the fruit goes bad. Coffee growers have two methods to choose from: the dry and wet methods.

The dry method is an old technique that uses the sun to dry out the cherries for several weeks. Workers occasionally rake through the cherries to ensure the sun reaches every side, and no mold grows. The coffee must register no more than 11% moisture.

a man drying coffee beans, using a large spade to spread the coffee beans

The wet method uses machines to remove the pulp from the cherry. Then, the cherries are separated by weight using water. The light cherries float to the top, and the heavier ones sink.  The cherries then sit in fermentation tanks for 12 to 48 hours to remove the parenchyma, a thick, gooey substance on the bean.

machine wet processing coffee cherries with water gushing in from the top

Cherries that were processed using the wet method need to be dried after the parenchyma has dissolved. Once the beans reach a moisture level of 11%, they are called parchment coffee.    

Milling the Parchment Coffee

Before export, parchment coffee needs to be processed. First, a hulling machine processes the coffee. If the beans were dry processed, the device removes the entire husk. Wet processed beans are a little easier, in that the machine only needs to remove the parchment layer.

Sometimes, companies will polish their beans. This process removes any remaining silver skin from the beans. Although the beans look prettier, there isn’t much of a difference between polished and unpolished beans.   

Finally, workers sort the beans by weight and size. Companies only export beans that pass inspection and throw the rest out. Many companies sort the beans by machine and hand to ensure every bean is fermented correctly and is the correct size and color.

Exporting the Coffee

The newly named green coffee is now ready for export. In 2018, countries around the world exported nearly 175 million 60kg bags of coffee.  

Why We Roast Coffee

Green coffee isn’t ready to be turned into the liquid black gold we all know and love. A green coffee bean is spongy, soft, and smells like grass. If you tried to brew it, the resulting liquid would be overwhelmingly bitter and acidic. But green beans last longer than roasted ones, without losing any flavor.

Roasting creates a chemical reaction in the green beans as they experience a quick increase in temperature. Whether you’re going for a light, dark or medium roast changes the exact moment you remove them from the heat.

4 different coffee roast colours

The type of roast will also affect the flavor of your final cup of joe. Coffee can be full-bodied, light and acidic, or smoky and bitter.    

Once roasted, coffee beans don’t stay fresh for long. The sooner you brew them, the better your coffee will taste.   

Roasting Materials

Now that you’re all caught up on where coffee comes from, we need to talk about what you’ll need for home coffee roasting. The list is surprisingly short.

Green Coffee Beans

You’ll need to source some green coffee beans. But unlike ground coffee, you won’t find them in your neighbourhood supermarket.

Your best bet is to either go to your local coffee shop or order online. Either way, you’ll need to make some decisions about what flavours you want.

The best green coffee beans for home roasting are also some of the most interesting ones on the market. The deciding factor is your tastebuds. Do you prefer coffee with herbal notes? Then maybe roast some India FTO Cherry AA beans. If you like notes of caramel, you’re better off buying some Indonesia Sumatra GR1 TP.

close-up photo of green coffee beans

Many coffee companies also offer tasting sets of green coffee beans. Especially for new home roasters, tasting sets are useful to discover more about your taste buds without committing to a big bag.

The great thing about home roasting is that if you don’t like the result – you can just try again with a different variety of bean! Home roasting is a fantastic way to explore new coffee roasting profiles from the comfort of your house.

A Note on Sustainability

If you’re a coffee lover and an earth lover, you might be interested in sourcing sustainable, fairtrade green coffee beans. 154 companies have joined the sustainable coffee challenge, and Fairtrade International is active all over the world.

By homebrewing, you’re already doing a service to the environment. One of the coffee industry’s most significant contributors to waste is the use of single-serve plastics, like coffee lids and stirrers. 

Its other environmental impact happens when companies clear large swaths of rainforest. The Rainforest Alliance is an international organization dedicated to protecting our rainforests. If you see their seal on your green coffee beans, that means your company of choice has taken steps to protect the environment. 

Fairtrade International focuses more on the human side of coffee production. If you’re interested in supporting companies who treat their workers fairly, keep an eye out for their symbol.

A Roaster

There are five ways to roast coffee beans at home.  

  • Fry them on the stove using a skillet or a wok.
  • Bake them in your oven on a cookie sheet.
  • Repurpose your hot air popcorn maker.
  • Use your stove-top popcorn maker.
  • Buy a fancy roasting machine.  

Roasting machines cost anywhere from $80 to $400, so there are options for every budget.

Depending on what you use to roast your beans, you might also need an outdoor stove or grill, a baking tray, or a sieve or metal colander.

Regardless of whether you choose a more DIY approach or decide to use a roasting machine, you’ll need a way to store your coffee after roasting. Use the most airtight container you’ve got.  Glass mason jars are perfect for storing home-roasted coffee beans.  

Coffee Roasting Techniques

Now that you’ve gathered your equipment, it’s time to learn how to roast coffee beans at home. First, we’ll break down the different stages the roasted bean goes through as it’s heated up, and then we’ll walk you through how to roast your beans on the stove, in the oven, and with a popcorn popper.

The 10 Phases of Roasting

  • Phase 1: Green: The starting point.  
  • Phase 2: Yellow: An aroma of grass will fill the air as the bean’s colour changes.
  • Phase 3: Steam: As the remaining liquid evaporates, you’ll see steam rising from your beans.
  • Phase 4: First Crack: When you hear crackling, that means your beans have started roasting!
  • Phase 5: City Roast: The sugars inside the beans are continuing to caramelise.
  • Phase 6: City Plus Roast: Also known as a medium roast, at this stage, the beans will start to expand, sugars caramelise, and oils release. 
  • Phase 7: Full City Roast: If you like slightly darker medium roasts, you’ll probably enjoy a full city roast. Continue to the second crack for an ever darker option.
  • Phase 8: Second Crack: The second crack will be even louder and more intense than the first one. Keeping your beans on the heat throughout the second crack will give you a full city plus roast.
  • Phase 9: Dark Roast: Also known as a French roast, this is the last stage before you ruin your beans. You’ll see smoke as the sugars burn off and the beans start to break down.
  • Phase 10: Burn: If you’ve reached this stage, you’ll have to start over.  If your beans are too burned, you won’t be able to brew them.
roasting process chart showing 6 coffee beans from drying to dark roast beans

Especially if you’re shooting for a dark roast, prepare the room you’re roasting in for a lot of smoke. Open windows and make sure the area is well-ventilated. Also, take care when handling your roaster, regardless of what method you choose.

Your beans will be literally roasting when they come out, so don’t touch them with your bare hands!

Try Out Your New Roasting Machine

Using a roasting machine is probably the easiest option. Most roasting machines come with instructions, and they do a lot of the work for you. You can click here to read our reviews on home coffee roasters

Roasting machine. Spinning cooler professional machine. Industry concept . Freshly roasted machine coffee beans.

Roasting machines work by swirling hot air around and keeping the coffee beans in constant motion. This method ensures that the beans are all evenly roasted.

To use your roasting machine, you’ll need to add the correct amount of green beans. Your instruction manual should give you an exact amount.

Next, turn on the machine and watch out for colour changes. Once your beans are the perfect shade of brown, turn off the power and pour them into a sieve.

Keep stirring them in the sieve until they’re only just warm. You did it! Store your beans in an airtight container and use them within a week.    

Using a Hot Air Popcorn Maker

Strangely enough, roasting coffee beans with a popcorn popper is the most recommended DIY strategy. It’s easy, quick, and fun.

First, gather your materials. You’ll need

  • 1 Air Popcorn Popper
  • ½ cup of green coffee beans
  • 1 baking tray big enough to spread your beans out on
  • Thermometer
  • 1 Mason Jar for storing

Next, preheat your popcorn popper for about 30 seconds. Once it’s hot, pour the beans in. Keep a close eye on your beans, watching for a color change, oil, and smoke. Once they’ve reached the phase you’re aiming for (use the roast guide below to help you), turn off your popper.

Quickly pour the beans onto your baking tray and spread them evenly. Every so often, give them a shake to speed up the cooling process.

If you like, use the thermometer to check the internal temperature of your beans. You can compare the temperature to the colour, which will help you learn precisely which colour corresponds to which roast.

That’s it! Once they’re cool, store your beans in a mason jar. Leave the lid off for around 12 hours to allow your beans to degas fully.    

The Stove-Top Popcorn Maker Option

If you’ve got a stove-top popcorn maker lying around, here’s another way to use it.  

You’ll need these materials:

  • 1 stovetop popcorn maker
  • 1 outdoor grill or stove 
  • Green coffee beans
  • 1 baking tray
  • 1 thermometer

It’s best to work outside if you’re using this method. Outdoor grills and stoves can cause fire and gas hazards inside.

Once you’re all set up outside, preheat the popper until it reaches 400 degrees Fahrenheit. Pour in your green beans (the amount depends on your popper’s size and how much coffee you want to drink).  

Next comes the fun part. Turn the handle and make sure you keep the beans in constant motion. Don’t get too distracted. Keep an eye on the colour of the beans and any signs of oil or smoke. 

Once the beans have reached your desired roast level, turn the popper off and pour the beans onto your baking tray.

Shake the tray occasionally to get your beans to cool down faster. Once they’re completely cool, store them in your mason jar. It’s best to leave the lid off for around 12 hours so your beans can degas. Just don’t forget to seal the jar up after – if they’re left out in the open too long, the beans will go stale.  

Roasting Coffee Beans on the Stove With a Skillet

This method works best with a gas stove. If you’ve one, here’s the rest of your supply list:

  • A thick pan, preferably steel or cast-iron
  • 1 sieve
  • Green coffee beans
  • Wooden spoon
  • Oven mitts

Open up your windows and make sure your extractor fan is running at full tilt. Place your pan on high heat (you’ll want it to be around 450 degrees Fahrenheit). 

Once the pan is hot, add your beans. Don’t overcrowd the skillet; your beans should be in a single layer with room to move.

As the beans roast, use your wooden spoon to keep them moving. Keep an eye on the colour, and remove the beans from the heat when they’re the perfect shade of brown.

If you’re hankering for a dark roast, use a different method. You won’t be able to get the heat high enough on your stove, and the smoke can also cause problems inside.

Once the beans are perfectly roasted, pour them into your sieve. Give them a good stir, then let them cool and degas. Lastly, store them in your handy mason jar.

The Oven Option

Using an oven is perhaps the most challenging DIY method. It’s harder to judge the beans’ colour, and you won’t get as much smoke. But it still works. You’ll need a few materials:

  • A vegetable steamer, a perforated pan or a wire mesh colander
  • If you’re using a vegetable steamer, you’ll also need a cookie tray
  • Oven mitts
  • 1 sieve
  • Green coffee beans
  • 1 wooden spoon

Preheat your oven to 500 degrees Fahrenheit. While it’s heating up, prepare your beans. Regardless of what you roast the beans in, you’ll need to make sure they’re in a single layer. This helps them to roast more evenly.

If you’re using a vegetable steamer, place it on a cookie sheet before it goes in the oven. You won’t need a cookie sheet with a perforated pan or a colander.

Once you’ve preheated the oven, slide your beans in (don’t forget to wear oven mitts!) and close the door. Unlike the other methods, you won’t have a clear line of sight, so listen carefully for the crack. Around two minutes after the first crack, take a quick peek at the color. 

If you’re using a colander, you might want to give it a quick shake every minute or so.  

Once you’re happy with the colour of your beans (or it’s been 20 minutes), remove the pan from the oven wearing your mitts, and pour the beans straight into your sieve.

Stir the beans around with a wooden spoon until they’re cool. It’s best to do this over a sink since some chaff will fall off the beans as they cool down.

Store them in a mason jar, leaving the lid off for 12 hours to allow them to degas, and then you’ll have freshly roasted beans in the morning.

Degassing Your Beans

It’s best to let your beans degas to achieve the most flavourful cup of coffee possible. Around 40% of the gas escapes within 24 hours.

Of course, there’s also a question of how to degas your beans while also keeping them fresh.  Each type of bean and roast is different and requires experimenting. Most roasts need around 12 hours to degas.

Just don’t forget to seal your mason jar up after the beans have degassed.

Types of Coffee Roasting

Now that you’ve got the basics of how to roast coffee beans at home, you need to know what makes each coffee roast type unique.

There are four standard categories of roasts: light, medium, medium-dark, and dark, which are determined by their internal temperature after removal from the heat.  Each has a distinctive flavour profile.    

4 different roasted coffee beans from green beans on the left to dark roast on the right

Light Roasts

Otherwise known as light city, half city, or cinnamon roasts, a light roasted coffee will have a mild, pleasant taste. If you’re looking for a light-bodied cup with a hint of acidity, you’ll probably enjoy a steaming mug of light roast coffee.

Another plus for beginners is that you’ll only need to get your beans to around 400 degrees Fahrenheit.

Because you remove your beans from the heat during the first crack and before the oil releases, they’ll still be dry and light brown.  

Medium Roasts

Popular types of medium roasts include city roast, city roast plus, American, and breakfast roast. It’s one of the more popular roasts in the US because while it has more flavour than a light roast, it’s less intense than a dark roast.

A roast is classified as medium when the internal temperature reads between 410 and 428 degrees Fahrenheit, which is still easy enough for a home roaster to reach. 

If you’re aiming for a medium roast, take your beans off near the end of the first crack and when they start to take on a darker brown color.

Medium-Dark Roasts

Unlike the first two levels, medium-dark roast beans have a light coating of oil. The flavors are more pronounced than a medium roast, and the beans are slightly darker. This category encompasses many popular roasts, including full city, full city plus, and Vienna roast.

You’ll need to reach an internal temperature between 437 and 446 degrees Fahrenheit. Turn off the heat just before the second crack for the perfect medium-dark roast.

Dark Roasts

Only for the most adventurous, dark roasts include the French roast and Italian roast. They’re full of flavor and body but challenging to master.

To reach the required internal temperature of 464 degrees Fahrenheit, you’ll have to let your beans smoke a bit. Be vigilant, and don’t let the temperature top 482, or your beans will burn.

Espresso Roasting

Achieving the perfect roast for your espresso can be challenging. Because the process of making an espresso intensifies the flavour of the beans, a dark roast might be too intense for anyone except a true coffee adventurer.

Italian baristas swear by a medium or medium-dark roast. They offer more flavor than a light roast but stop short of some dark roasts’ intense bitterness.

Don’t despair if your first attempt at an espresso roast falls flat. Just use the roast in your french press and try again next week.

Enjoy Your Hard Work

Now that you know how to roast coffee beans at home, you can enjoy a beautiful fresh cup of coffee every morning. The wonderful thing about roasting at home is that every batch turns out slightly differently.

Keep experimenting to find your perfect roast, and you might enjoy the journey as much as the destination.