Coffee roasting is not an art, but a craft. And that's why you can easily roast your own coffee at home. But to make sure it's delicious and not too dangerous, we've put together these tips for you.
Anyone who has ever been to a coffee roastery knows how much space roasting machines can take up. We roast on a 12kg roaster, which already weighs a good 500kg and is the size of a small car.
Our 1kg Probatino roaster is also well over 100kg, but still quite large. If you've ever been to a large roastery and seen a 250kg roaster, you'll find that these machines, with all their bells and whistles, are the size of a small house.
But now it's also possible to go much smaller. There are devices that are maximally the size of a shoebox, with which you can roast 50g or even several hundred grams at home. And that's really fun. There's hardly any other way to get as close to the product as when you roast coffee on the smallest possible scale.
A Small Adventure
We've tried various home roasting machines and introduce them on our YouTube channel. One thing up front – I had a blast. I usually roast on a 12kg roaster and advise other roasteries that have 5kg – 60kg roasters. These are sizes I'm used to.
But roasting a few grams now is somehow very exciting. Many things are more delicate, uncontrollable, faster, and – yes – sometimes simply more random. The background knowledge I've acquired over the years on larger roasters is being put to the test here. So if you have contrary experiences with the discussed machines or otherwise, please write to us in the comments section.
Roasting your own coffee is a small adventure at first. It smokes, it cracks, it gets hot, maybe things happen a bit uncontrollably, but you will like your coffee. Even if it's not as delicious as from elsewhere, the work that goes into it tastes really good.
With our little guide, we show you how to roast a solid coffee at home right from the start.
Time and Temperature – how long and how hot to roast?
First of all, we have to disappoint you – we cannot give you exact information on time and temperature. Not because we don't want to, but because we can't.
Temperature
Just as my grind size is not your grind size, my temperature is not your temperature. I recently roasted on two different roasters of the same type. However, the temperature was always slightly cooler on roaster A than on roaster B.
This was mainly due to the fact that roaster A had a different temperature probe installed in the roaster. One that was thinner and thus more sensitive. Roaster B had a thicker and thus more sluggish probe installed.
If we want to measure the temperature in a manual popcorn roaster, we need a temperature probe for it.
So which was the right temperature? I would say neither. Honestly, I don't care what the "exact" temperature is – the main thing is that we stick to one temperature and go from there.
180° in a popcorn roaster* are probably different from 180° in a drum roaster. It always depends on what and where is being measured. Therefore, temperatures are irrelevant. If you already roast at home, you have already gained experience and can use that as a guide. If you are starting from scratch, we recommend setting the manufacturer's suggested temperature.
Roasting Time
Time and temperature are interdependent when roasting.
The hotter the temperature, the faster the roast.
The cooler the temperature, the slower the roast.
Giving exact times doesn't help much here, as different roasting machines apply heat to the beans differently.
In general:
4 minutes would probably be too short, the taste would be quite harsh because the coffee has not undergone enough sugar transformations.
20 minutes is quite long, especially for small quantities – we'd just bake the coffee and literally hollow out its flavor.
Anything in between seems delicious. Shorter roasts for filter coffees and lighter coffees, slightly longer roasts for espresso. That would be universal – but time and temperature specifications unfortunately are not.
Tip Box: Time and Temperature
- we roast the bean from the outside in – and that requires energy
- too little energy = roasting takes a long time = the taste becomes flat
- too much energy = roasting is difficult to control and the taste is unbalanced
- try roasting the same coffee for 8, 10, and 12 minutes, then taste it. That's how you'll find your favorite
What is the right quantity?
One of the great advantages of roasting is that many steps are simply explainable and logical. This also applies to the question of how much quantity should be put into the roasting drum.
Small quantities heat up faster – large quantities heat up slower.
Makes sense.
Especially with small roasters, popcorn roasters, etc., there is hardly any energy stored in the system (roaster wall, bottom, lid, etc.). Most of the energy input comes from hot air or direct contact heat.
When you put green coffee into the roaster (=roasting system), the system first loses energy. Green coffee at 20°C ambient temperature enters a hot environment and first absorbs heat.
When you bake lasagna, preheat the oven, then open the door and put in the cold lasagna, the temperature in the oven first drops. The same thing happens with roasting.
So, if you put a large quantity into any roaster, the roasting will take longer because you are drawing energy from the system.
If you add a small quantity of coffee to the roast, you draw less energy from the system and can roast faster.
Is there a correct amount of coffee?
You already know the answer – no, there isn't. Everything is system-dependent. For now, stick to the manufacturer's specifications. Then see how long the roast takes and refer to the points mentioned above.
If you make adjustments to the batch size, then definitely make them clear. If you roast the 1st batch with 100g and the 2nd batch with 110g, the difference is much smaller than if you roast, for example, 100g and 150g.
When I encounter a new roasting machine during roasting consultations, I always do some more extreme tests, exploring the strengths and weaknesses of the system by choosing larger differences in batches or temperature. This way you will reach your goal faster.
Tip Box: Quantity
- start with the amount of green coffee specified by the manufacturer
- then change the quantity with a minimum difference of 25%
- orient yourself to the times mentioned above – if the roast is finished after 4 minutes, the roaster is either much too hot, or the quantity is much too small
- if the roast is still not finished after 20 minutes, then reduce the amount of green coffee or turn up the temperature
First Crack and Development Time
Over several minutes, you approach the first crack, the first pop, or simply the cracking sound. Then, when the pressure in the coffee bean is so great that it has to escape, you hear a distinctly quieter or louder cracking sound, depending on the roasting system.
Softer coffees tend to crack as if you're crushing peanuts. We often hear this crack in Brazilian coffees.
For harder, denser coffees, such as those from Kenya, the crack is much louder and more explosive, like fireworks going off.
It's fun to hear this crack and associate it with the coffees. Pay attention to this crack and you will understand your coffees much better.
When does the 1st Crack begin?
Did I mention that it's really fun to listen for the 1st Crack? Depending on the flavor you're aiming for, your crack will come earlier (lighter coffees, because faster roasting), or later (more developed coffees, espresso for example).
The 1st Crack comes in increasing intensity, similar to a normal distribution in this picture. First, it's just a single bean that starts and cracks (far left of the picture). Then a second, a third, and a fourth join in (first line from the left). After that, it gets more intense. As soon as you hear the first triplet, i.e., closely spaced crack-crack-crack, that's when we mark the 1st Crack (second line from the left).
The cracking (1st Crack) resembles a normal distribution
This way, we can be sure that the whole batch is starting to crack now. It takes some practice, nerve, and patience not to mark the 1st Crack right at the first crack.
Shortly after the 1st Crack, the whole batch takes off, and it cracks more and more evenly; the majority of the beans (third line from the left) are cracking simultaneously now.
After that, the curve drops until no more cracking can be heard. Should you continue to roast longer and especially hotter at this point, you will approach the 2nd Crack, which is significantly quieter and sounds more like a crackling. For our guide here, we will omit the 2nd Crack.
Why is the 1st Crack important?
Because it provides us with a simple and precise means to roast coffees individually. If I strictly roast only by time, for example, all filter coffees for 10 minutes, all espressos for 14 minutes, and all dark roasts for 18 minutes, then I am doing the coffee a disservice. This is because many coffees behave differently during roasting.
Since we roast many coffees for others, we gain experience with a wide variety of coffees. The more different coffees we roast, the better we can predict the behavior of an unknown green coffee.
Example:
I take a pulped natural from Brazil and roast it for 10 minutes, as this is my "filter recipe." Then I roast a coffee from Kenya for 10 minutes.
The two coffees behave completely differently and taste completely different too. The 10 minutes for the Kenyan coffee might make it appear in its best light – fruity, balanced, well-integrated acidity, while the Brazilian coffee might already be burnt, as it is much softer.
So, if we get used to marking the 1st Crack for every coffee instead of roasting according to total roasting time, the coffees will taste much better quite quickly.
And what happens next?
After the 1st Crack begins the so-called development time. This is the time the coffee spends from the beginning of the 1st Crack until the coffee is removed from the roaster.
An example:
I roast a coffee that cracks after 8 minutes. I mark the 1st Crack. Now I roast for another 90 seconds and then remove the coffee from the system. The development time would therefore be 90 seconds, in relation to 480 seconds. So we can calculate the percentage development time, which in this case would be 15.8% (90sec out of 570sec).
| Roast time until 1st Crack | Development time | Total roast time | % Development time |
| 480 seconds | 90 seconds | 570 sec | 90sec/570sec = 15.8% |
So what does that mean now?
A shorter development time of approx. 5% can mean that I
- almost certainly under-roast the coffee
- create few aromas,
- the coffee still tastes green and unpleasantly nutty to corn-like
A medium development time of approx. 8-10% can mean that I
- get a coffee with a lot of aromatics,
- more acidity, tea-like texture, and
- few roast notes.
A longer development time of approx. 12% plus can mean that I achieve
- intense aromatics,
- more body and roast notes
- and a heavy sweetness
A long development time of approx. 18% plus can mean that I achieve
- many roast notes, fewer light, floral and fruity aromatics,
- less acidity, less texture,
- but a lot of body and dark sugar notes
All these statements are so often "without guarantee" because they depend on the respective roasting system. However, I have tried to treat them as generally as possible, so that it is more universal than very specific.
Tip Box: 1st Crack and DT
- the time from 1C to the end of the roast, which you determine, we call development time
- if you want to adjust the roast profile, first change the time after the 1C and leave everything before it the same as in the previous roast
- different coffees have different development times
- always roast with a pad, pencil, and stopwatch
- mark the 1C and start a lap time on your phone, so you have the total roast time and the DT on one display
The Roasting Curve
Everything that happens in the system during roasting can now be measured with temperature probes and digitally recorded via an interface. This so-called roast log software helps us to roast as precisely and consistently as possible.
In the past – just a few years ago – this software was hardly widespread. However, programs like Cropster or Artisan have experienced immense growth in recent years. More and more roasteries are not only relying on their gut feeling, but also want to convert their data into information, visualize it graphically, and thus learn even more.
We read roast profiles from left to right. The x-axis shows time, the left y-axis shows bean temperature, the right y-axis shows the Rate of Rise (RoR) – the energy increase per 30 seconds.
Three roasting curves from the Kaffeemacher roastery
Temperature probes at various points in the roasting apparatus measure the temperature and record it in software. In the example above, you see three curves from our roastery.
The blue curve is the Ichamama, a light roasted filter coffee.
The yellow curve is our Feingeist, a specialty espresso.
The red curve is an extended full-automatic coffee that we roast on behalf of a private label customer.
The roasting language of the three profiles could not be more different. In terms of time, the coffees vary between 9:10 and 17:30 minutes. The final temperature is also different in each case. What becomes very clear, however, is the temperature increase – very steep for the Ichamama, somewhat flatter for the Feingeist, and significantly slower for the fully automatic coffee.
We will look at how you can draw such a curve yourself, without complex roasting software, elsewhere. What is important up to this point is to understand that differences in time and temperature have a massive impact on the final product.
Wolfram Sorg from Backyard Coffee has written an enlightening article on profile creation: https://www.backyard-coffee.com/blogs/kaffeewissen/entwicklung-eines-kaffees.
Which beans for which taste?
It is probably one of the most beautiful tasks in a roastery: green coffee selection. At the same time, however, it also has many consequences. Depending on the selection of green coffee, you open up or limit the range of application of the chosen coffee.
Green coffees differ in density, size, and shape. They all roast slightly differently.
Highly acidic coffees are delicious for filter coffees, because we dilute them with a lot of water and a light drink is created. However, these green coffees are probably not for everyone when it comes to espresso.
But also vice versa – simpler, tend to be nutty-sweet coffees can make a great espresso, but possibly a somewhat monotonous filter coffee.
This is where you come in. Because every roasting language is individual. Everyone who roasts has their own interpretation of how the coffee should taste in the end.
Green coffee selection – we're opening our warehouse
You have to start somewhere, and buying a whole 60kg bag is probably not purposeful. So we are now also selling 1.5kg and 3kg bags of green coffee. These are the same ones we use in our assortment. So if you want, you can, for example, roast our classic Dreispitz blend.
Which of our coffees do we use for what:
| Filter | Espresso | Taste | Acidity | Texture | Price 1kg | |
| Kenya, Ichamama | yes | not to our taste | fruity, berry | a lot, juicy | medium-heavy and soft | 16.95CHF |
| Brazil, APAS | possible | definitely | nutty, chocolatey | little, mild | soft and gentle | 6.40 CHF |
| Nicaragua, Santa Rita, Leica Washed | yes | possible | sweet-sour, citrus and nutty | medium | round | 13 CHF |
| Ethiopia, Bulga | yes | yes | complex, fruity, intense | medium | a lot, tea-like | 16 CHF |
| Rwanda, Simbi | yes | possible | black tea, honey, oranges | medium | tea-like | 16 CHF |
| India, Faith Estate, Robusta | not to our taste | certainly | kick. woody, nutty | hardly any | heavy | 5.90 CHF |
| Honduras, 18 Conejo | yes | possible | limes, stone fruit, dark chocolate | a lot | juicy | 13.65 CHF |
| Peru, NORCAFE | possible | yes | citrusy, balanced | medium | round | 6.80 CHF |
| Henrique, Demeter, Brazil | yes | yes | chocolate, light acidity, nutty | mild | heavy | 13.65 CHF |
You already know which coffee suits you best – if you need some inspiration, we have put together a small guide for you here.
After roasting: Cooling and storing
We recommend roasting with a stopwatch as standard, marking the 1st Crack and writing down the data. This way, you can create references and compare them again and again.
You determine the end of the roast. Once you have reached the desired development time, remove the coffee from the roasting system.
After that, the coffee must be cooled as quickly as possible. Not with water, that is only done with large quantities, but with air. In our academy, we use these fans that suck air downwards and thus
a) draw away the smoke
b) cool the coffee quickly
You can also just take a pasta sieve and cool the coffee in it. Important: always keep it moving and blow on it to cool the coffee down.
This is how we stop the physical and chemical processes of roasting and prevent uncontrolled further roasting.
The silverskin on the green coffee bean (whitish), adhering, and on the table after roasting. The airflow must remove the silverskin from the system so that it does not catch fire.
How long does the coffee need to degas after roasting?
For our coffees, we recommend:
- min. 7 days for a filter coffee
- min. 14 days for an espresso
However, we usually do a cupping for quality assurance after 24-76 hours. We pour 12g of coffee with 200g of hot water, wait 4 minutes, break the crust and slurp the coffee.
As a guideline, you can use this:
long roast = long degassing time
short roast = short degassing time
It's best to taste the coffees regularly, every day after roasting, and discern the differences.
This way, you'll quickly find the time that's right for you.
What coffee scientist Chahan Yeretzian says about freshness, we discussed in this video.
How can I improve?
Another fascinating aspect of roasting is its totally analog nature. Unlike a digital camera, where you can simply delete a bad photo, you have to master the analog camera, otherwise you've used up space on the film roll. That's roasting.
You put green coffee into the system, roast it, done. Once the coffee is roasted, you can't roast it again. Well, you could, but it makes no sense. You'll just burn the coffee and that's no fun.
Green in, brown out. If you've done everything right, the result tastes good. If not, well, try again. Learning by doing, or as a colleague once said: learning by burning. So there's always a bit of adrenaline involved in roasting, and that's probably why it holds such a fascination for so many people.
Record data in the roasting log
To truly understand how you're improving, you need to record your data. By hand, in an Excel spreadsheet, no matter, the main thing is that you include this data:
- which green coffee
- amount of green coffee
- starting temperature (if possible, otherwise irrelevant)
- time to 1st Crack
- development time
- end temperature (if possible, otherwise irrelevant)
- weight of roasted coffee
By weighing the roasted coffee at the end of roasting, you determine the roasting loss. Expect 14-20%, depending on the type of roast. Especially with simple roasters without a temperature display, it's worth measuring the weight. This gives you a feeling for how much material you roast away.
We have created a simple roasting log for you, which you can download as a PDF and fill out. The more precisely you fill in the data, the more you can compare the different roasts and improve.
Taste, taste, taste
All the numbers can look great, but if the coffee doesn't taste good, even the prettiest numbers are useless. Therefore – challenge yourself and taste every batch, and do so in a standardized way.
How can you proceed?
- always taste after x hours
- this way you compare coffees of the same age
- grind 12g of coffee and pour 200ml of water over it
- approx. 96°C
- use your own water, whether it's hard or soft
- in this case, it's about getting a feel for your craft
- it's best to reconcile this by not changing the basic constants (for now)
- steep for 4 minutes, skim the crust, start slurping after approx. 8 minutes
- or, you have your own ritual, e.g., you brew a French Press or a filter coffee. All that doesn't matter, the main thing is that you always do it the same way. Consistency, consistency, consistency.
We are your coaches
If you have read everything, learned a roasting technique, and now want our feedback, please send us a sample of your work. We will taste it and give you feedback. Our feedback is honest, because we want you to be able to improve.
So: roast, practice, roast, and if you want, we are there for you and will help you figure out how to do it even better.
Tips, Tricks, Safety
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Green coffee selection
- in our Kaffeemacher shop, we offer most of the green coffees we roast ourselves
- You will also find green coffees at Ingo from Roast Rebels
- Kafischmitte also offers green coffees for sale
-
where to roast?
- if you roast in an apartment or house – then definitely under an extractor hood with an open window
- roasting produces a lot of smoke and the silverskin detaches from the green coffee, which may then swirl around
- always keep the coffee moving, so it doesn't burn
- if you have a terrace, balcony, or garage, we also recommend roasting there. For everyone's sake.
-
which devices can you recommend?
- we are still holding back on recommendations because we are still in testing mode
- it's best to subscribe to our YT channel, where we will present the tested machines
- Ingo from Roast Rebels sells home roasters in the mid-price segment and tests them for you
- we ourselves do not sell machines, but we enjoy testing everything that works
- so if you have any tips on what we should look at, please recommend them in the comments.
- you can find the popcorn pot we used here on Amazon*
*We bought the popcorn pot. This is a basic principle for us in all tests. Because we want to evaluate all devices neutrally and without external influence. The link is an affiliate link to Amazon. If you order something via the link, it won't cost you more – but our machine testing fund will fill up a little.
