Have you ever thought about roasting your own coffee? Well, it’s a lot easier than you might think. With a few simple pieces of equipment and some green unroasted coffee beans you can start roasting your own coffee minutes before you brew it. Home roasting is fun and it can save quite a bit of money if you’re a regular coffee drinker. There’s nothing more satisfying than sipping a cup of your own fresh-roasted beans.

Here we’ll cover the four most common home-roasting methods including: stovetop, electric popcorn popper, oven, and specialty home-roasting machines. Each of these methods has the potential to produce great tasting coffee, though some are easier to master than others.

Whenever roasting coffee in your home there are a few things to keep in mind:

  • Coffee requires high temperatures to roast and therefore both coffee beans and equipment must be handled carefully. Oven mitts or work gloves work great.
  • When coffee is roasting, especially dark roasts, it can produce smoke with a pungent odor. This smoke will slowly increase as the temperature rises. It is a good idea to have some sort of ventilation. You can roast in a garage or on your porch.
  • Because coffee is roasted at such high temperatures (up to 450°F or more) there is some risk of fire if the beans are mishandled. Once the roast is underway the beans MUST be kept moving until the have been cooled to the touch (the oven-roasting method is an exception). Beans being roasted begin to generate their own heat after a certain point in the roast and will heat until they catch fire if they are not cooled in time. So, it is very important to remember that hot beans must be stirred! Having a fire extinguisher on hand is a good idea.
  • You should be present at all times during the roasting of your coffee beans. Roasting is a delicate process and requires attention. So, always keep an eye on the beans.

Before we get into the specifics of the different roasting methods, let’s review some basic roasting concepts.

Depending on the roasting method you choose, the entire roasting process can take from between 10 and 30 minutes, though, it’s usually 15 to 20 minutes.

Probably the most important factor in the outcome of your roasting will be the type of green beans you choose. Coffees from different countries and growing regions have a wide range of characteristics. The best way to get to know the differences between various beans is to experiment with a variety of coffees and compare their flavors. Beyond this, practicing the art of blending different roasted coffees is another excellent way to familiarize yourself with coffee characteristics.

During the first half of the roasting process, the beans are essentially drying out. Green coffee has a moisture content of around 10%, although it can vary considerably based on ambient humidity, the origin, and age of the beans you’re using.

In the early stages of roasting, you may see some steam escaping from the beans and the coffee will have the smell of fresh grass. At this stage the beans are very dense and do not have much ‘coffee-like’ flavor yet.

Slowly, the beans will lose their green color and begin to turn a tannish/brown. You will also detect the smell of baking bread at this stage. The beans are on the verge of actually roasting rather than drying.

As the roast advances you will hear a crackling and popping sound. Once this sound begins, roasting has commenced. The popping sound (called the ‘first crack’) is the result of residual water inside the bean breaking free from carbon dioxide. This pinot makes the beginning of ‘pyrolysis’ where the beans begin to generate their own internal heat and smoke starts to emerge from the beans. Sugars inside the beans are caramelizing and the true coffee flavors are developing. It is at this stage that ‘chaff’ or the outer skin of the bean will separate and fly off the surface of the bean. The roast can be stopped anytime after pyrolysis has begun, depending on how dark you want your coffee.

The cracking noise will slowly subside and the beans will get darker and darker. After a short while a ‘second crack’ will begin to be heard which represents the breaking of the internal structure of the bean. Once this ‘second crack’ has started you have entered the category of ‘dark roast’. The smoke in this stage is more opaque and has a strong coffee smell.

The ‘peak’ of the second crack is about as far as you’ll want to go. Much beyond this will produce a thin, burnt tasting cup (though some people truly enjoy this charred taste). It is important to note that not all roasting methods can heat the beans to this point so some experimentation is necessary.

As you familiarize yourself with the roasting process, there are several ‘mileposts’ to watch for:

  • The color and smell of the steam and smoke.
  • The sound the coffee makes.
  • The color of the beans.

Every bean will roast differently and the interaction of these ‘mileposts’ will tell you a lot about what is happening to the beans as they roast. As your techniques advance, you can begin to track the time and temperature of the roast by keeping a ‘roasting log’ that tracks the major variables of the roasting process.

The final stage of roasting is cooling the beans. Because the beans produce their own heat during the roast, it can take a couple of minutes to cool them down completely. The beans must be kept moving while cooling or they may heat themselves until they catch fire. This means you’ll want to cool the beans about a minute before they appear ready.

Let’s start with the most traditional method: Stovetop. Stovetop roasting (which also works great over a fire) is the best way to really see the roasting process unfold. Coffee was first roasted in pans over campfires. Even until the early 1900’s most people roasted their own coffee at home this way.

To begin you’ll need:

  • A pan. You can use a cast iron skillet, wok, frying pan, or better yet, a hand-crank stovetop popcorn popper such as the Whirley-Pop. Please note that whatever pan you choose it will no longer be suitable for food once it has been used to roast coffee.
  • A metal colander for cooling the beans after roasting. Avoid plastic colanders, which can leach ‘plastic flavor’ into the cooling beans.
  • Oven mitts or gloves to handle hot items.
  • A wooden spoon for stirring beans while roasting and cooling.
  • Of course you’ll need ¾ cup to 1 cup of green, unroasted coffee beans.

Start off by preheating your pan to 500F. Once the pan is heated, pour in your beans and cover the pan. Once the beans have entered the pan they MUST be kept moving throughout the entire roasting process or there is risk of fire.

Roast the beans on high heat, keeping them in constant motion. Every minute or so you can uncover the pan and stir the beans with your wooden spoon. You should always recover the pan quickly so heat isn’t lost. This is also a good time to check the color and smell of the beans.

As the beans roast you will begin to detect changes in their look and smell. The smells will change from grassy to baking bread and finally to coffee.

As the beans brown you will begin to hear a crackling and popping sounds. As the sound grows, smoke will begin to come from the beans. At this time ‘chaff’ will separate from the beans and may fly around some. We will remove the bulk of the chaff during the cooling phase so don’t worry.

Any time after this point will produce drinkable coffee.

Keep checking the beans and note their color and the look and smell of the smoke.

Once the beans have reached their desired darkness, you’re ready to cool. Remember that the cooling process itself can take one to two minutes. This means that the beans continue to roast after you’ve begun cooling. So, begin cooling about a minute before they look and smell ready. This process will take some practice so don’t worry if you don’t get it right the first time.

To cool the beans, dump them into the metal colander and stir them with your wooden spoon. If you have a small fan you can cool the beans faster by turning it directly on the beans. Chaff, the outer skin of the bean, will be blowing around at this point. You’ll want to remove as much of this as possible (try brewing a cup of chaff-tea if you want to find out why).

Once the beans have cooled to the touch, they are ready to cool and store.

The next method of home roasting we’ll look at is the use of an electric popcorn popper. This is the easiest method for a beginner to achieve great tasting coffee with more consistency and less practice. It also has the advantage of blowing the chaff out of the beans automatically. Additionally, electric popcorn poppers can be regularly found at thrift stores for $2-$5. The most popular type of popper for roasting is the West Bend Poppery II, but any type of popper with the correct hot air inflow (see below) will work.

There are two VERY important things that must be kept in mind when using this roasting method:
First, though they work well, electric popcorn poppers are not designed to roast coffee. So, not only will it void any warranty you may have on your popper, but also it is not uncommon to burn out the motor after 20-50 roasts. Also, not all poppers have the ability to roast coffee well. As the motors slowly degrade they will become unable to maintain the high levels of heat necessary for roasting so you may have to try multiple poppers to find one that works well. The voltage in your homes outlets can vary from time to time and this can also affect your ability to get consistent results (some more advanced home-roasters use a voltage variac machine to achieve constant power. These machines also allow you to adjust the voltage going into the popper which can give you greater control over the roast).

The second thing to remember is that the popcorn popper MUST have the correct air inflow chamber. THIS IS CRITICAL! Hot air must enter the roasting chamber from the SIDE walls of the chamber NOT FROM THE BOTTOM! If you attempt to roast coffee in a popper with the incorrect hot air inflow you are at great risk of causing a fire.

To begin you’ll need:

  • Electric popcorn popper with SIDE ENTRY hot airflow.
  • A metal colander for cooling the beans.
  • Oven mitts or gloves.
  • A bowl to catch chaff blowing out of the popper.
  • A wooden spoon for stirring the beans while roasting when necessary and for cooling.
  • About a half cup of green coffee (use whatever the recommended volume of popcorn for the popper is).

Start your popper and place the chaff collection bowl under the opening of the popper (this bowl will not only collect chaff but also any stray beans that may pop out during roasting). Slowly fill the popper with the recommended volume of beans (usually about ½ cup). As the hot air begins to circulate, the beans should rotate a bit with the flow of air. If the beans do not rotate at the beginning, give them a gentle stir with the handle of your wooden spoon until they begin to spin on their own.
As the roasting begins, chaff will separate and fly off the beans and smoke will appear.

When the smell of the smoke changes from ‘baking bread’ to coffee and the beans start to crackle, begin to pay close attention and be ready to cool your beans when they have reached the desired roast.

Any time after the cracking begins you can cool the beans, but the longer you go the darker roast you’ll get. Don’t forget to allow for one to two minutes of cooling time when the beans will continue to roast on their own.

When you’re ready to cool, stop or unplug the popper and IMMEDIATELY pour the beans into your metal colander and stir vigorously for a minute or so or until the beans are cool to the touch. Any remaining chaff can also be removed at this point by simply blowing on the cooling beans.

When you are done roasting, wipe out the popper with a dry cloth to prevent the build-up of oils that can not only slow down your next roast but also creates a fire hazard.

The next roasting method we’ll discuss is oven roasting. Though oven roasting can produce good drinkable coffee, it is probably the least consistent and most difficult home-roasting method. This is primarily because it is impossible to keep the beans in constant motion and therefore the beans do not receive consistent heat on all sides. Also, when the beans are stirred a great amount of heat is lost through the open oven door.

Despite these difficulties, experimenting with different roasting methods is the best way to learn roasting techniques and become a better, more consistent roaster. So don’t be afraid to give it a shot!

To begin you’ll need:

  • An oven or toaster oven.
  • A cast iron skillet or baking sheet.
  • A metal colander.
  • Oven mitts or gloves.
  • A wooden spoon for stirring the beans.
  • ½ cup to 1 cup green coffee beans.

Preheat your oven to 450F. Put about a half inch of green coffee in the bottom of your skillet or baking sheet. Place the beans in the oven and shut the door.

Once the beans are in the oven you’ll want to stir them with your wooden spoon every minute or two. When you do this it is important to DO IT QUICKLY because a lot of heat is lost through the open oven door. If the beans are not stirred often then they will develop burn spots.

After a few minutes you will begin to see smoke coming from the beans and you’ll hear the beginnings of the cracking. Watch the beans closely from this point on because they will develop fast.

As the color and smell of the beans change keep stirring and get ready to cool (don’t forget that the beans keep roasting after you’ve removed them from heat).

When the beans have reached the desired roast remove them from the oven and dump them into the metal colander. You MUST stir the beans continually during cooling; this will also help remove the chaff that loosened during the roast.

Keep stirring the beans until they are cool to the touch.

Once you have mastered the above techniques you might want to move on to a machine specifically designed for roasting coffee at home. Though home roasters can be pricey ($100-$750+) they have a number of features that can really improve your roasting success:

  • Home roasting machines usually have ample power to achieve darker roasts.
  • They have chaff collection devices
  • They can roast considerably more coffee at a time than some traditional methods.
  • They often have built-in cooling capability
  • Because they are made for roasting coffee they can often achieve greater consistency than some traditional methods.

If you are thinking about investing in a home-roasting machine, it is important that you do your research and decide what features you’ll be looking for and what price range will work for you. Any of the top machines will produce great coffee though they all have strong and weak points. If you have further questions regarding home roasting machines or home roasting in general please contact us and we can provide you with more information.

The leading home roasting machines are:

  • Caffe Rosto- A great ‘fluid-bed’ roaster with plenty of power
  • Hearthware- One of the best selling roasters out there
  • Hot Top- A real drum roaster with ½ lb. capacity. Pricey and smoky but great.
  • Alpenrost- Another drum roaster that works well and is much cheaper than the Hop Top.
  • Zach and Dani’s- This roaster has built-in smoke eliminator.

Remember that though these machines work great, with practice you can achieve a comparable roast with the traditional home-roasting methods.