Slow Coffee Club

Home brewers of Belgrade · Saturdays since 2019

Home roasting

Roasting at home, with the windows open

Coffee arrives at the roaster as a hard, grassy, green seed. Twelve minutes of heat turn it into something that smells like caramel and chocolate. You can do that in your kitchen with a secondhand popcorn machine or a heavy pan. It is messy, smoky, occasionally disappointing and enormously satisfying. Here is everything we’ve learned, mostly from Stefan’s mistakes.

Why bother

Cheap beans, fresh coffee, and a new hobby

Green coffee keeps for a year or more in a cool, dry cupboard. Roasted coffee is at its best for about a month. If you roast at home, you can keep a small shelf of interesting green coffees and roast a week’s worth at a time, always fresh.

It is also cheaper. We buy green beans from Zeleno Zrno, a tiny importer in Novi Sad that sells by the kilo to home roasters, at roughly 1,800 to 2,600 dinars per kilo for very good coffees. Remember that beans lose about 15% of their weight as they roast: a kilo of green gives you about 850 grams of roasted coffee.

Mainly, though, it changes how you taste. Once you’ve stopped one batch thirty seconds earlier than another and tasted the difference, you never think about a coffee the same way again.

What happens in the roaster

The six stages of a roast

Times are for a 90 g batch in a popcorn machine. A pan is slower and less even, a professional drum roaster more controlled. Your nose and ears will tell you more than the clock.

  1. 0:00 – 3:00

    Drying

    Beans go from green to pale, smelling of cut grass and hay. Water is cooking off. Chaff starts to fly.

  2. 3:00 – 4:30

    Yellowing

    Beans turn yellow then tan. The smell shifts to bread dough and basmati rice.

  3. 4:30 – 7:00

    Browning

    Sugars caramelise. Cinnamon-brown colour, smells of toast and caramel. Some smoke.

  4. ~7:00 – 7:45

    First crack

    Audible pops, like popcorn, as steam bursts the bean. Around 196 °C. Coffee is now drinkable.

  5. + 45 s to 2 min

    Development

    The time after first crack. One minute gives a light filter roast; two, a medium. Stop when it smells right.

  6. ~10:00 +

    Second crack

    Faster, quieter snaps like crackling cereal. Oils appear, heavy smoke. Dark roast. Stop soon, or it burns.

Roast curve for roast number 31 Bean temperature over time for a 90 gram popcorn-machine roast of a washed Burundi. The temperature rises quickly to about 140 degrees in two minutes, then more slowly, reaching yellowing at 4 minutes, first crack at 196 degrees at 7 minutes 30 seconds, and the beans are dropped at 203 degrees at 8 minutes 45 seconds. 50° 100° 150° 200° 0123456789 min drying browning dev. yellow · 4:00 · 170° first crack · 7:30 · 196° drop · 8:45
Roast #31, washed Burundi, 90 g. Bean temperature from a cheap probe thermometer pushed into the bean mass, read aloud every thirty seconds by a patient volunteer.

Method one

The popcorn machine

A hot-air popcorn popper is basically a tiny fluid-bed roaster: hot air from below keeps the beans moving and roasts them evenly and quickly. It is the cheapest good way to start. Stefan’s cost 1,800 dinars secondhand.

Choose the right kind. You want a popper with air vents in the side walls of the chamber, so the air swirls the beans. Avoid any model with a mesh or slotted floor directly over the heating element — chaff falls through onto the element and can catch fire.

  1. Set up outside on a balcony or by an open window, on a stable surface, with an extension lead and a metal bowl to catch chaff.
  2. Preheat the empty machine for one minute. This was Stefan’s big breakthrough after thirty roasts.
  3. Add 70–90 g of green beans. Too few and they fly out; too many and they won’t move. They should just about circulate on their own.
  4. For the first two or three minutes, stir with a long wooden spoon to help them along. As they dry and lighten, they will start swirling by themselves.
  5. Watch the colour, smell the smoke, and listen for first crack around 6–8 minutes. Start counting from the first pops.
  6. At your chosen development time, switch off and tip the beans straight into a metal colander.
  7. Cool them fast: toss them between two colanders in front of a fan, outdoors. They should be cool to the touch within three minutes. Slow cooling keeps roasting them.

Method two

The pan, the old way

Before anyone in Belgrade bought roasted beans, plenty of households roasted their own on the stove. Dragan remembers his mother doing it in a hand-cranked iron cylinder over the wood stove on Sunday mornings, the whole stairwell smelling of it. A heavy pan works the same way, if less evenly.

  1. Use a heavy cast-iron pan or a thick-bottomed wok, never a non-stick one. Heat it on medium for five minutes.
  2. Add a single layer of beans, 120–150 g, and start stirring immediately with a wooden spoon. Do not stop. Stirring is the whole method.
  3. Keep the heat medium. Too hot and the outsides scorch while the insides stay raw; you’ll see dark spots and smell burnt sugar early.
  4. First crack typically arrives at 10–15 minutes. The roast will be uneven — some beans darker than others. That is normal and, in a džezva, honestly rather nice.
  5. Tip the beans into a colander, shake outside to blow off the chaff, and cool quickly.

Pan-roasted coffee is rustic. It is not the way to taste the subtleties of a delicate Ethiopian. It is a wonderful way to make the smoky, sweet, slightly uneven coffee of a Balkan grandmother’s kitchen, ground to powder for the džezva.

The roast log

Stefan’s roast log (selected)

Every roast gets a line in the notebook. Here are the ones worth learning from, good and bad. “Loss” is weight lost during roasting: under 13% is usually too light, over 18% heading dark.

Popcorn machine unless stated. FC = first crack. Times in minutes:seconds from beans in.
# Date Coffee Batch FC Drop Loss Verdict
112 Jun 2024Brazil, natural100 g—11:3011.8%Stalled, never properly cracked. Flat and papery. “Baked.”
220 Jun 2024Brazil, natural80 g8:509:4013.1%Cracked! Grassy and sour. Too light, too short a development.
46 Jul 2024Brazil, natural80 g7:409:1014.6%First genuinely drinkable roast. Nutty, sweet. Neighbour impressed.
73 Aug 2024Colombia, washed90 g6:208:5017.9%Took it too far on purpose. Bittersweet chocolate, good in the moka.
1119 Oct 2024Ethiopia, washed80 g7:108:0013.4%Lemon and black tea, but a hint of grain. Needed 20 s more.
1423 Nov 2024Peru, washed150 g, pan12:4014:3015.8%Pan experiment. Uneven but lovely in the džezva. Dragan approved.
191 Feb 2025Ethiopia, natural80 g6:507:5013.9%Chaff caught on the lid rim and smouldered. Roast fine, nerves not.
2317 May 2025Guatemala, washed90 g7:208:4015.0%Toffee and apple. Matched the shop roast almost exactly.
272 Jan 2026Kenya, Kiamuri Ridge90 g7:008:0514.2%Blackcurrant, tomato leaf. The roast that made the club go quiet.
315 Mar 2026Burundi, Ngozi Hilltop90 g7:308:4514.8%Preheated, fan-cooled. Cranberry and brown sugar. Best yet.
3520 Jun 2026Honduras, anaerobic80 g6:407:3513.6%Wild ferment went vinegary when roasted light. Not for us.
3829 Oct 2026Kenya, Kiamuri Ridge90 g7:058:1014.4%Second attempt at #27. Resting for Saturday’s blind test.

Read this part

Safety, seriously

Roasting means high heat, flying chaff and smoke. None of it is dangerous if you respect it, and all of it can be if you don’t.

  • Never leave a roast unattended, not even for a moment. A batch can go from second crack to flames in under a minute.
  • Keep a fire extinguisher or fire blanket within reach. Since February 2024, the club rule is that it sits beside the roaster. Never use water on an electrical fire.
  • Ventilate. Roast outdoors, on a balcony, or under a strong extractor with windows open. Roasting smoke contains carbon monoxide and irritants, especially at darker roasts. Keep pets, particularly birds, well away.
  • Manage the chaff. It is papery and flammable. Empty the chaff bowl after every batch and wipe the lid rim.
  • Popcorn poppers are not designed for this. Running one at these temperatures will shorten its life and may void any warranty. Let it cool fully between batches, and retire it if it smells of hot plastic or the cord gets warm.
  • Hot beans are very hot. Use oven gloves and metal colanders. Never cool beans in plastic.
  • Tell your neighbours. Not a safety rule, strictly. But a bag of coffee prevents a lot of misunderstandings about the smell of smoke.

Resting

Freshly roasted coffee is full of carbon dioxide and tastes harsh and gassy. Leave filter roasts at least three days — ideally five to ten — before brewing. Darker roasts are ready sooner. Store in a bag with a one-way valve, or a jar with the lid loosely closed for the first day.

Buying green coffee

Start with a forgiving, washed Central or South American, or a Brazilian. They roast evenly and taste good across a wide range. Save the Ethiopians and Kenyans for when you can hit your target reliably — they are delicate and reward precision.

Keep notes

Date, coffee, batch size, time to first crack, drop time, weight before and after, and how it tasted a week later. It feels tedious for about three roasts and then becomes the most useful thing you own.